Tuesday, October 25, 2016

How to Master Electronic Chart Navigation with the Starpath eNav Trainer

Electronic chart navigation means using a software program on a computer or other device that is designed to display electronic charts with built in electronic charting tools and a connected GPS receiver that shows your vessel moving across the chart. There are dozens of such programs available offering various levels of sophistication to assist the navigator in both route planning and navigation underway. Once mastered, these electronic charting systems (ECS) provide the state of the art in navigation safety and efficiency for all vessels, power or sail, commercial or recreational.

But as with all new technology, there is much to be learned before we can take full advantage of all the resources the programs offer. We start with the manuals, and oftentimes detailed videos on the functioning of the programs, to learn the basic operations, such as how to load and view charts, and set up optional displays. And we learn the tools they offer such as setting waypoints and making routes, measuring range and bearing, using range rings, and more.

We learn that most of the ECS programs will also accept AIS signals telling us the location and motion of nearby traffic, and we learn the ECS offers various alarms and alerts we can set for safe navigation underway.

Much of the basic use we can learn from the static situation of just having our vessel at a fixed location on the chart, and then we have to head out onto the water to see how these resources operate when underway.

How eNav Trainer Can Help

The Starpath eNav Trainer offers a way to master the use of ECS underway from the safety of your armchair, desk or classroom. The key is a realistic simulation of the GPS signals you would receive if you were indeed underway and moving. Sitting at your computer, your program thinks you are actually on the water. In another window on your computer or from the screen of your phone or tablet, you have the vessel controls that drive the boat your ECS is monitoring. Just as when on the water in your own boat, you turn right on the controls, and you see your boat turn right on the echart display. Speed up, slow down, drive however you choose. If you run into a charted buoy, you won't get hurt, but you will have something to think about!

With this simulation resource, you can practice with the navigation tools of your program, many of which are vessel centered, and you can practice setting various alarms, and see them work in action. You can make routes and practice following them. For example, often there is an option to set a range ring on a way point and let the program automatically change to the next waypoint along the route when you cross that range. The eNav simulation is a way to see such operations in action under various conditions.

To add more realism to the challenge—and demonstrate the value of practice—the eNav Trainer also adds current flow to the waterway. With current present, you vessel will not make good the course you are steering, so you can practice following a route in these conditions. The eNav simulates a heading sensor, so your echart program knows which way you are headed, as well as the COG you are making good at any time. Learning to read and interpret these two crucial outputs is another thing you can master with this tool. You can even practice docking in current.

The eNav Trainer also offers crucial practice with collision avoidance using either real or simulated AIS traffic. If you have access to live AIS signals—there are numerous Internet connections that provide these—then you could drop your own vessel into, for example, a very busy San Francisco Bay, Puget Sound, or Chesapeake Bay, and practice simply driving from one side to the other without violating the Navigation Rules. Or choose the Port of Shanghai or Singapore for even more difficult traffic challenges.

But is it likely best to start out slower with eNav's simulated AIS traffic. When you choose to run several vessels in a simulation, each will appear as an AIS target to the others. Practicing on your own, you can open two control panels, choose one for your own vessel and the other for the AIS target. This way you can present the approaching AIS target as you choose, and then study collision avoidance with it, testing the CPA (closest point of approach) alerts your program offers.

With two or more navigators practicing together, each can control their own vessel, and monitor it in their own ECS program. They can be the same brand of ECS or different. Then each will see in their program their own vessel as well as the other, which will appear as a moving AIS target. Both then practice collision avoidance together.

When practicing from remote locations, the two (or more) navigators can communicate via the eNav's simulated VHF radio, which offers crystal clear audio connections between users.

In short, there are unlimited training exercises users can work through to master the navigation tools of their chosen ECS, just as they will appear when underway. This can lead to expertise and confidence in the use of electronic navigation that is hard to come by without many miles of actual experience—not to mention that you can practice all the scenarios you do not ever want to encounter underway.

In Summary...

The Starpath eNav Trainer is a realistic GPS, AIS, and heading-sensor simulator designed for individuals or groups so they can master the full use of their chosen electronic charting systems (ECS) and to practice realistic navigation maneuvers with other moving vessels, either simulated or real, viewed as AIS targets on their screens.

This Internet based simulation can be used with any brand of ECS, using raster or vector echarts, for any part of the world. Simultaneous users, driving individually simulated vessels, in a mutually chosen waterway, can be located in the same classroom, or they can be located in different parts of the world. They just set their ECS chart displays to that waterway and see each other on the chart.

Modern electronic charting systems are sophisticated software with many powerful options for enhancing safe navigation. Many of these tools, however, are difficult to learn and practice without being underway. With eNav Trainer you can practice navigation and collision avoidance in current and in traffic, learn how various automated safety and convenience features and alarms of your program actually work, practice various display options, and so on. With real-size vessel icons, you can even practice docking or coming along side another moving vessel. When simulating multiple vessels, you can jump the control from one vessel to another to see how each perceives the other in various maneuvers.

Details of how the eNav Trainer is setup in your computer are given at eNav Trainer Help.

Monday, October 24, 2016

Network Connections to Navigation Software

In anticipation of our new Starpath eNav Trainer (an integrated, multi-vessel GPS, AIS, VHF, and heading sensor simulator), we have here a few notes on how to make a network connection to your navigation software.

The process is very similar for all software, with differences only on how you access the needed input screens. Then each program has separate ways to verify the connections. The use of network connections in navigation software is increasing, because more instruments offer this option to interface onboard sensors as well as make external Internet connections for various aspects of actual navigation.

In this case, we are using this connection to provide a powerful training tool that will help mariners learn and master the special features of their navigation software of choice, and then go on to provide practice with realtime interactions with other simulated vessels viewed as AIS targets. With it you can also learn more about AIS protocol as well as study collision avoidance with AIS targets. The AIS targets studied can be either those provided by eNav or live AIS signals received by another connection.

To make this connection, you will need to know the IP (Internet Protocol) address of the eNav server, along with the port number used on that IP. An IP address is the same as a URL for a webpage. In some programs you can input the URL text or the IP numbers; some accept only the numerical IP address. 

The IP and port numbers used by eNav are dynamic numbers that will change for various users, but once you have your session set up in your navigation program they will remain unchanged. You can close the program or switch to live GPS (via a serial or USB connection), and then later return to simulation practice.  Navigation programs store connections once made, and they remain available until you choose to remove them. Within each program there is the option to enable or disable specific connections as needed. To switch to live GPS, the eNav connection should be disabled.

When taking part in the eNav Trainer service, the IP address and port will be provided to you on a web page that looks like this:

The eNav user's Vessel Assignment page that provides the network connection data. We use TCP (Transmission Control Protocol) for the connection, which is sometimes written TCP/IP. 

To illustrate the network setup process, we give several examples below, first as a text outline, followed by a short video showing the actual steps in action.

To have your navigation software recognize the connections outlined below, the eNav link must be active on the eNav server. If you have the emailed link showing the IP and Port (shown above), then that means the connection is active. 

If the connection is not active, or the input numbers were not correct, the connection will not be completed. Some programs alert you to this error, others do nothing. No possible damage can be done. When the connection is active and entered correctly, it will log on immediately and start receiving the signals. 

You can set up and confirm the initial connection to eNav without having your vessel positioned where you eventually want it (anywhere in the world) and without the appropriate chart(s) installed. After this initial connection, If you check your program’s GPS position report to see “where you are,” you will find that you are located in Puget Sound, Seattle, WA (47º 43.0’ N, 122º 25.0’ W), just north of Shilshole Bay Marina.

That is the default starting location for all vessel simulations, which is on US RNC chart: 18446 or ENC US5WA14M  (Puget Sound, Apple Cove Point to Keyport).

This note covers just this one step of setting up the network connection. The process of setting up vessel location and other information is given here: Control Panel and vessel set up. Using the procedures described there, you can move your vessel to any location and make other specifications for the simulation and navigation training. 

To end a simulation session using any navigation program, first use the eNav vessel control panel to anchor your vessel, then you can just close the program, and when you return you can carry on without further set up. f you want to use another source of GPS for actual navigation, then go back to the network setup window and disable the eNav TCP connection and activate your new GPS source. Usually you do not have to remove it, just disable it. Then you can turn it back on when ready to practice more.

1. From the main menu (top left), select Configure Vessel and Electronics…

2. Select Data Ports, then Port Settings

3. Press Add Network Port and select

      Type = NMEA 01830 Over TCP
      Label = your choice of vessel name
      Address = (use actual one provided to you)
      Port = 38424 (use actual one provided to you)
      Options = Listener checked, Talker and Repeater un-checked
      Press OK, and close the window.

You should see a yellow band on the top of screen with notification of a simulated GPS signal. This notice can be closed. 

To confirm the signals, close the Instrument Ports window, and open Troubleshooter. In the top line Port, select your vessel name. You will then see the sensors detected: GPS, Compass, AIS. You can close or view actual data if you choose. Then return to main program and zoom out on the chart to see where your vessel is located. See Control Panel and vessel set up for next steps, which include positioning it as you choose.

To disable the connection and save the configuration, just uncheck the Listener box.


1. Start the program and be sure to select Navigation mode when booting.

2. The Connection Wizard should show up open, but if not select it from the main menu (top left). If not listed there, then reboot the program and be sure to start in Navigation mode.

3. In Connection Wizard, check Manual Port Configuration, then Next

4. Check Add/Configure TCP Connection ( Advanced), then Next

      Distant IP Address = (use actual one provided to you)
      Distant IP Port = 38424 (use actual one provided to you)

You should see the data stream in at this point, Press Next to confirm that you are receiving GPS, AIS, and Heading sensor data, and then Close.

Zoom out on the chart to see where your vessel is located. See Control Panel and vessel set up for next steps, which include positioning it as you choose.


1. From main Expedition menu, select Instruments / Number of Network connections, and increase the number active by 1, and press OK

2. Back to main menu Instruments / Serial and network ports.

3. Select your new network number on the left

      Instruments = NMEA 0183
      Connection = TCP Client
      Address =  (use actual one provided to you)
      Port = 38424  (use actual one provided to you)
      Boat = your choice
      Redirect and Commands on the right not needed
      Check Use position fix and Validate checksums
      Default NMEA sentences should be ok. (we use GGA, RMC, GSA, HDT, GSV, AIVDM, and AIVDO)
      Click Apply. 

To confirm the data, press Raw data. You should see the NMEA sentences streaming in. Then OK and OK.

Zoom out on the chart to see where your vessel is located. See Control Panel and vessel set up for next steps, which include positioning it as you choose.


1. Click the wrench icon, then Connections, then Add Connection

2. Click Network then

      Protocol = TCP
      Address =  (use actual one provided to you)
      DataPort = 38424  (use actual one provided to you)
      Checks in Control checksum and Receive data on this port. No check in the Output on this port.
      then Apply

You should see the top right GPS signal icon go green. To confirm the data, in the same connections window, choose show NMEA Debug Window. It will likely open behind what you are looking at, so move that window to see the data, then you can close both of them.

Zoom out on the chart to see where your vessel is located. See Control Panel and vessel set up for next steps, which include positioning it as you choose.

There is an Enable check box in the list of ports that can be used to disconnect and save the configuration for later use.


Polar View

1. From the menu Ship, select Port Manager

2. Click Add, then

      Enter a vessel name if desired (not crucial)
      Select Network Client
      IP address:port   :   38424  (use actual values provided to you)
      Autodetect SeaSmart unchecked.
      Direction = Input
      Protocol = TCP
      Retry delay (sec) = 2 (not crucial)
      Connect timeout = 4 or 5 (not crucial)
      Activation = Manual
      Press Add

3. The Port Manager window will then show up with your network connection. Highlight it and then press Start. And close that window.

You may not see any change at this point, but you can check the input from the main menu / Ship / NMEA Console, and then you will see the signals stream in.

To see your vessel on the chart, from main menu, select Live Ship Mode, and then your vessel will appear on the chart. To disable the simulation, from the Port Manager, click stop.  See Control Panel and vessel set up for next steps, which include positioning it as you choose.

Wednesday, October 12, 2016

Wed Oct 12, 2016: Time to Start Your Barometer Calibration

We have a nice Low approaching the Pacific Northwest so beyond its other implications, ie gusts to 50 kts forecasted for Puget Sound, and much rain, we can look to the brighter side, and take this opportunity to calibrate barometers.

Just start a log and write down every few hours or so what your barometer reads... and do not move its location, meaning do not change its elevation above sea level.

Then by end of week end you can look up the local pressure reported for your nearest location and compare the two.

We expect a drop from about the present 1024 down to 993 tomorrow around 4 to 6 pm.

GFS forecast for Seattle Area

In Seattle area, check your pressures at WPOW1, the West Point Lighthouse, which presents a graph like below, but also tabulated data.

You can also use custom pressure links we have set up at www.starpath.com/local.

Or check "UW meteograms" from link at www.starpath.com/insidepassage for another prediction. Note their statement that these take a few minutes to build once requested.

For those away from Seattle, find your closest reference station at www.starpath.com/barometers

UW meteogram. 

Here is the latest weather map, from 5 am this morning.

Here is our main reference for barometer use and calibration

If you get good data and want help analyzing it, then just send us a copy of it to helpdesk@starpath.com  ie two columns, one of time and date, one of pressure from your barometer. Include your lat lon and the height of your barometer above the ground. We can find the ground height from here.  Record pressures to the nearest tenth of a mb.

Monday, October 3, 2016

Great App Idea from UKHO

Successful navigation depends on accurate resources, meaning in large part the hydrographic products such as nautical charts, coast pilots, light lists, tide and current tables that we find in every nav station, pilot house, and bridge around the world. There is an immense amount of data compiled in these charts and documents, much of which is subject to change, so it is obvious that any way mariners can help the agencies keep these up to date is a step forward that benefits all users.

All hydrographic offices around the world offer some means of reporting discrepancies found in their products. There are online forms that can be used, or a call to the local ATONs office at the USCG is always appreciated. But these days, the first thing that comes to mind when we have a common problem to solve is: "There ought to be an app for that!"

Well... as it turns out there is an app for that, and we can thank the United Kingdom's Hydrographic Office (UKHO) for it. In the Apple App store it is called H-Note. It is a free iOS app that very conveniently lets users prepare a report of any discrepancy in charts or publications direct to the UKHO.


I have test tested this, and they got back to me the next day, with an acknowledgment.  Furthermore, I have since spoken with them and indeed we can use this app to report discrepancies or additions for any chart or publication produced by an official national hydrographic office.  They do this because they distribute charts from many nations for all waters of the world, so they have close ties with all related agencies worldwide.  Naturally, we would not expect them to address discrepancies in third party charts or unofficial navigation pubs, which are beyond their control.

Typical input screens are shown below.

The key here is convenience and a consistent format. And indeed they are asking for all the key information they need to address the report. The Publication Affected input even has a drop down that lists all of the UKHO pubs, but you can overwrite these with the pub in question, if it is not on the list.

The idea is beautifully simple. Using the app, mariners can report chart or nav pub corrections with a quick message from their phone. Underway you can actually tag the location with your device's GPS to precisely mark the location of your observation, though you may not be able to transmit it till you have an email connection. You can also take a picture of the real object you are commenting on as well as a picture of the charted object in your ECS and include those with the report.

The app works by preparing a formatted email with your added images and then sending it to UKHO. Thus you do not actually need an Internet connection to file a report, but just an email connection. With something equivalent to Iridium Go, you would "Submit" the report from the app and then it would go out as an email to your high seas email program in your computer, and wait there till your next connection satellite connection. Then it would send automatically with your next incoming or outgoing mail batch. This assumes that while underway you have set your phone to use the mobile mail service as your outgoing mail server, which is common practice with this type of equipment.

On inland or coastal waters, the message would just sit in your outbox till your next phone network connection underway. In short, the process of sending a report is so easy that one is much more likely to actually send it. Following up on a logbook entry after a long or tiring voyage is less likely. On a day sail, you can report that your favorite buoy is off station as you sail by it... pronounced "boy" in this case.

US Counterpart

Actually we have had in the US a very similar system for efficient reporting of hydrographic discrepancies for many years. It is called NOAA's Nautical Discrepancy Report System.

The form is then submitted over the Internet and serves the same purpose as the UKHO app. But since learning about the UKHO app, I can see the value in having this as an app. For one thing, with the app you do not have to be online at the time you file the report, and the app can read your GPS position automatically. Also drop down menus with as much filled in as possible ahead of time is always a help. It is hard to beat just pulling your phone out of your pocket and sending a report as you spot a need.

Maybe NOAA will consider something like this, or maybe they already are. In the meantime, there is a way to get this onto your phone. You can email (or txt) the link to the NOAA Discrepancy Form (http://ocsdata.ncd.noaa.gov/idrs/discrepancy.aspx) to yourself, and then check mail or messages on your phone. Clicking the link in your phone will open that page in a browser in your phone, and at that point you can save that link to your phone's home screen. On an iPhone, you do this with the Send-to link at the bottom; then choose Add to Home Screen. Enter an email address (so you can get an answer back), and in two clicks you are ready to fill out the report and send it.

I have tested this NOAA form by sending in an obscure minor correction and did indeed hear back the next morning with an acknowledgment and encouragement to send whatever we discover.


And now, in a sense, to my main point, which I will only mention for now, as we are preparing more notes on this topic.

We are working on new training materials for electronic chart navigation, which has led us to even more study of electronic navigation charts (ENC). For years we have appreciated the challenge to navigators of moving from traditional paper charts to electronic charts—especially to the use of ENC vector charts based on IHO standards.

These are the charts of the future for all navigators, and indeed they are the daily charts in use by many professional mariners around the world. The ENC have tremendous facility for providing much more information than possible on a paper chart, but they do not always reach the full potential of information they could. In some cases a charted object actually includes less information than we get from the corresponding traditional printed chart symbol. With the on going active help of mariners using the products, these issues can be resolved.

In short, I look at this Hydrographic Notes app idea pioneered by the UKHO as a step toward essentially cloud sourcing the hydrographic information needed to keep the ENC presentations optimized and up to date, and we heartily look forward to its popularity.

Monday, July 18, 2016

Tropical Storm and Hurricane Advisories using FTPmail from NWS

In a recent note I explained how to get these crucial Hurricane Advisory reports underway using email request to saildocs. For completeness, we should also look at the primary source for getting the same information directly from the NWS using ftpmail.

I am reminded to do this because I just discovered that there is an excellent presentation of the ftpmail service in the back section of the NWS publication on radio fax schedules (rfax.pdf), and you would not guess that from the title—in fact, you would not guess it from the Table of Contents, either, because it is in Appendix B, and there is no Appendix B in the Contents. Nevertheless, it is there and it is very helpful.

So with this document you not only get the latest HF frequencies and broadcast schedules for conventional HF FAX weather map transmissions, you also get the ftpmail instructions with interactive links, as well as a long list of other marine weather resources.  It appears they have updated this pdf  with regard to the HF schedules and it does have a table of contents for the fax schedules, but other parts of the publication are not fully updated.

To help focus on the FTPmail part, we have pulled out that section and added a table of contents for the ftp products, and removed some outdated and redundant sections. You can get this document here:

This is an important program to know about and test using.  It includes essentially all NWS products, both maps and text—for local waters as well as oceans.  For some graphic map products, saildocs still has the advantage as they reduce them by a factor of 2 before sending, so this is a big factor for sat phone communications.  But saildocs do not offer all the maps that are available, so we need the ftpmail service.  We have made another convenient pdf for getting either the larger size maps from NWS directly or by email request to saildocs for the reduced file size.

Sunday, July 10, 2016

Tropical Cyclone Advisories by Email Request

If you sail in hurricane zones or their broader waters, you might eventually see something like this:

The unforgivable red arrows on this map mark two entirely different things. The horizontal ones show the directions  of motion of the Lows; the down bound ones are associating the text notice with the systems they refer to.

The NWS tells us to see the Advisory, because they know that no map they make, nor any map that anyone makes, will tell us what we need to navigate in the vicinity of the path of these storms. (We do have a cyclone danger area map available by rfax, but it does not layout the winds).  We also know that the grib formatted GFS forecasts for these systems are not dependable, especially in the early days of formation... and we have to interpret "not dependable" as including "very wrong." 

So it is crucial that we know how to get these Advisories underway.... and we can, once again, be very grateful for the wonderful services of saildocs.com, as they will send them to us promptly with an easy request—though we should keep in mind that saildocs is just tapping into the NWS's long established FTPmail program, which is the primary source.

Send an email to query@saildocs.com and in the body of the text have these 6 lines

send met.12
send epac.disc

send epac.disc4
send epac.tech_advis4

send cpac.disc4
send cpac.tech_advis4

Then in a few  minutes you will get 6 emails back, all small text only.

The first is an overview with some TC data covering all of Metarea 12.  The second is the forecasters discussion of what they forecasted.

The data for Metarea 12 is given in 3 separate parts in the text file.
The "4" in the next requests identify the 4th Pacific storm of the season, which is Celia.  Blas is #3, and the next is Darby,  #5.  Change this number in the request to the number of the storm you are following.

The last two requests (Central Pacific) are only needed if you and the storm are west of 140W.

It is worth sending that email now to see what you get. You can cut and paste the above request lines, then remove any signatures that come up.

Here is what you get in the tech_advis report looks like for Celia, storm #4 of the 2016 Eastern Pacific season.  Note that each Advisory has a number so it is easy to keep track of what you have. They are issued every 6h.


WTPZ24 KNHC 100232

0300 UTC SUN JUL 10 2016




50 KT....... 30NE   0SE   0SW  30NW.
34 KT....... 80NE  60SE  60SW  80NW.
12 FT SEAS..140NE  60SE  60SW 110NW.


FORECAST VALID 10/1200Z 14.5N 120.6W
64 KT... 20NE   0SE   0SW  20NW.
50 KT... 40NE  30SE  30SW  40NW.
34 KT...100NE  70SE  70SW 100NW.

FORECAST VALID 11/0000Z 14.6N 123.0W
64 KT... 30NE  20SE  20SW  30NW.
50 KT... 50NE  40SE  40SW  50NW.
34 KT...110NE  80SE  80SW 110NW.

FORECAST VALID 11/1200Z 14.6N 125.3W
64 KT... 35NE  25SE  25SW  35NW.
50 KT... 60NE  50SE  50SW  50NW.
34 KT...120NE 100SE  90SW 120NW.

FORECAST VALID 12/0000Z 15.0N 127.3W
50 KT... 60NE  50SE  50SW  60NW.
34 KT...130NE 100SE  90SW 120NW.

FORECAST VALID 13/0000Z 16.7N 130.7W
50 KT... 60NE  50SE  50SW  60NW.
34 KT...130NE 100SE  90SW 120NW.


OUTLOOK VALID 14/0000Z 19.0N 134.5W

OUTLOOK VALID 15/0000Z 21.0N 138.5W




Our job is to

(1) Plot these positions on the chart and also sketch in the quadrants marking the 34 kt wind zones for the next 2 days or so. 

(2) Plot the extended 34-kt radii using the Mariners 1-2-3 Rule that expands the radii by 100 nmi for each 24h of forecast. If the radius is 20 mile now, it should be extended to 120 nmi for tomorrow at this time, and 220 miles for the next day. 

(3) Then try to maneuver to avoid this extended regions (Mariners 34-kt rule).

Note that the 34kt-wind Rule was designed for ships, so they obviously apply to small craft as well. It is not marking unmanageable conditions—experienced sailors can sail in 34 kt winds—but it is just a way to mark that region wherein the storm can change quickly either in direction or intensity. Staying out of that extended region (Mariners 1-2-3 Rule) is the recommended policy of both the NWS and the US Navy.  We have seen tragic loss of life at sea in recent times because that rule was violated.


Here is a video example of applying these Advisories in the echart program Expedition.


Deep back up  for all of this are the HF time tic broadcasts that include storm warnings every hour. These can be received by a simple shortwave receiver.

...AND, of course, the NHC has a Twitter feed for the E. Pacific @NHC_Pacific, but i do not know yet how we might use that.  It should be a useful way for fast info.

Friday, July 8, 2016

Wind Model Comparisons for Start of Pacific Cup

Before the start any data available are legal, but after the start only free public data are legal. We compare here a couple numerical predictions using Buoy 46026, located 18 mi west of San Francisco, of interest, for example, for the start of the Pacific Cup, San Francisco to Kaneoe Bay, Oahu.

Here is the data from Buoy 46026 followed by several numerical  forecasts. [When this post first went up, these were embedded links that updated automatically so we could follow the forecasts. Now we have replaced these with the complied data up till July 11, and these are static.] 

We are basically testing here the forecasts made at 18z on July 7 to see how they pan out for a day or so, with a main goal to simply illustrate one way to test models when preparing for a race.

These are both pictures captured from the NDBC site for Buoy 46026.

To follow are the forecasts presented as metorgrams at the location of Buoy 46026 from Expedition. Note that this function defaults to presenting the full time span of data from the latest download, but you can then zoom it for better comparisons.

So the procedure is, look at the wind speed and direction from the auto-updated pictures above and then look below to see how the models forecasted that back at 18z on Jul 7.

GFS at 28 km (0.25º) goes out >96h at 3h steps, updated every 6h

HRRR only goes out 15h at 1h steps, updated every hour
HRRR ony goes hour 15h, so very good for that period, but then need something longer.


NDFD  every 6h, 3h steps, 3 km, out

PW-GFS every 6h, 1h steps,

Note that several models call for 20 kts by 02 to 08z July 10, so it will be interesting to see who has this the closest... [Note added 7/1; we see the wind did indeed go to 20 kts at about the right time, though a bit later earlier or later than some predicted—but these are the details one might want to evaluate.  We did not know this at the time of the original post at 18z, July 7.]  

The hi res regional models do not go out far enough to see this back at 18z on the 7th.  They are intended to be run more frequently.  

Apply this for other cases you might care about. You can look at a buoy of your choice in the waters you care about at the NDBC site, and then load the various models in Expedition and just plot a meteogram at the buoy location and watch how the forecast pans out.

Note that you can check buoy data directly by sending this to query@saildocs.com

send http://www.ndbc.noaa.gov/mini_station_page.php?station=46026
Find buoy IDs at the ndbc site.

...and you will get back the data below, from which we see the models are pretty good, but NAM and GFS are off more than the others, and HRRR has timed out.

Station 46026
37.755 N 122.839 W

8:50 pm PDT 07/08/16
0350 GMT 07/09/16
Wind: WNW (300°), 11.7 kt
Gust: 13.6 kt
Seas: 3.3 ft
Peak Period: 12 sec
Pres: 30.03 steady
Air Temp: 56.8 °F
Water Temp: 56.3 °F

Wave Summary
9:00 pm PDT 07/08/16
0400 GMT 07/09/16
Swell: 2.6 ft
Period: 12.1 sec
Direction: SSE
Wind Wave: 2.0 ft
Period: 4.2 sec
Direction: WNW
Enter a station ID:

Or you can subscribe to that and get it back every hour, or 3h etc. Best to check with saildocs on that procdure.

Sunday, July 3, 2016

Light Lists—A Modern Look

The Light List (LL) is a crucial USCG publication for navigation for several reasons. The primary one is it includes information about the aids to navigation (ATONs, ie buoys, lights, day marks, radio aids) that is often not available on nautical charts, such as the nominal range and height of some lights, and other descriptions. This is especially true when relying on paper charts or using echarts in the RNC format, which are just graphic images of the paper charts.

Cover of the US Light List

A partial exception comes into play when using official US vector echarts (ENC) as these charts do include ATON data that are updated when the charts are updated, so in principle with automated ENC updates, you have all the latest ATON information as of about 10 days. They are updated every week, with about a 3 day processing time.  Thus an updated US ENC is much like having the latest Light List on board—but we are then at the mercy of our echart program that we count on to alert us that a new edition is available. 

But even with updated ENC, we should at least download one copy of the LL so we get all the extensive support tables and information that appears in the front part of the book.  We have long held that your best lesson on lights is to just read the 25 or so introductory pages to an US LL, including especially the Preface and Glossary included. There are also many helpful illustrations on these pages.  So the second important reason to have a LL is to learn how to interpret the lights, buoys, and other aids we run across on the waterway.  The LL is especially value for interpreting daymarks and it is growing increasingly important to understanding AIS aids. Those using USCG DGPS will also find crucial data there

But the point of this note is not the value of the LL, but how to get it onto the boat or your phone, and to keep it up to date.  The printed version is the same as it has been for years. Namely, once a year they publish an annual edition that is updated as of week 52 of the previous year.  The US government no longer prints these, but private companies have picked it up and do so.  They sell for about $53. The Canadian counterparts cost $30 printed, and the British Admiralty versions cost about $68. Both US and Canadian books are available as free pdf downloads, but not the Admiralty products.

We have then these options for getting the US LL into our computers or phones:

(1) US annual editions 

The point to stress here is this link gets you the full book, introduction and data, but it is not updated. This download will be the version of the LL that was up to date at the end of the previous year, ie week 52 of 2015. You get the same product here downloading in April as you would in November.

You have two ways to keep this Annual LL up to date. You can download just the changes that have occurred this calendar year since the annual edition was published, or you can download the full book as of the week of the download, but this file will not include the important front matter mentioned above.

(2) Summary of changes only

Using this solution you would have to have a copy of the annual edition as these are just the changes. These are small files (~250 kb). The practical application would be look up your light in the annual edition then do a quick check in the updates file.  You can do this fairly quickly because every ATON in US waters has a unique number, and that number is listed on the left of every entry, ie for ebook editions we just search on that number.

(3) Updated editions with optional front matter.

This seems a good approach. Just download the front matter once (~3 Mb) to have this important info somewhere available to you, then download the full set of data as needed to keep your LL up to date in one file. Then when underway you have just one file to look at. These files are about 800 kb.

The date of each of these is printed next to the download link in terms of weeks. The one I am looking at now is called Week 26 of 2016. Week 26 is June 27 to July 3, so this being the 4th is right. Again, the weekly updates can be up to 3 days late. It is also shown on each page of data as shown below.

When leaving for a trip, go to link (3) download both files (front matter and latest contents) and you are done. You have the front matter and you have the LL up to date at the time you leave.  That is the best we can do.  

Broadcast Notice to Mariners
If a crucial light does change once we are underway, then we can hope that it is reported by the USCG on their twice daily VHF broadcasts of the Notice to Mariners. They announce this on channel 16 then give the reports on 22A.  Publication 117 Radio Aids to Navigation tells when these are broadcasted if we want to focus on that without relying on the channel 16 announcement.

Or, for the navigator who has everything, you can request that all warnings and significant changes to ATONS be sent to your email directly at this page:

This is actually a wonderful service that you can try now, and then see how it might work for you with your onboard email service. It will also tell you when chart updates are available or other maritime notices... ie Navy bombing practice.

Canadian Light List
The Canadian books are also available with front matter and index separated from the main data, plus they offer the option to choose just the regional parts you need.  Thus when traversing Canadian waters as in the R2AK, you would select the regions needed and combine them for a custom version.

The Canadian LL is in principle updated monthly, but it is sometimes delayed as it must be released by the Canadian Coast Guard, which is a different agency than makes the actual updates.

When it comes to deciding the actual dates, we are almost certainly safe by just downloading those files, but there is some apparent inconsistencies in the date descriptions.  The individual sections are annotated with a date as shown below...

...but the actual pages in this section are each marked as last updated 5/16.
And when we check the front matter section, we get a bolder statement, with a still different date of 6/16.

In short, I think this means:  this LL was updated with all corrections as of June, 2016, and within the Straits of Georgia section, the last change (whatever it was) was made in May, 2016. This does not explain the date on the download page (2/16), which might be just an error. (They are checking that for us and I will learn shortly.)

Thus for our "truth meter" for deciding which light data were right in the short course, we can assign June, 2016 to the Canadian LL data.

But back to the ENC point raised at beginning...
If you own the latest official Canadian ENC charts for your region of interest,  the ATON data on them is the latest available and can be relied upon as being same as the LL or better.  This is also true for the US ENC. The official Canadian ENC come with 2 years of updates for the cost of $199 for all of BC.  Canada also has an email subscription service for chart and ATON updates at https://www.notmar.gc.ca/email-en.php

It is another matter to track down the  date of latest ATON data included with commercial echart programs that offer Canadian vector charts such as Navionics, C-map, Garmin BlueChart, MapMedia, and others.  These companies have a license to reproduce the charts, but no obligation to keep them up to date. When they do an update, we do not know what has been updated or what was the latest official chart was used. Some of these companies are known to be slow on updates, and in many of their apps you simply cannot tell what the latest edition actually is.  I have earlier addressed an issue related to that: Don't Blame eCharts for Anything.

Side note on ENC vs RNC.
We have several places pointed out the value of having ENC charts installed, even if you prefer routine navigation with RNC, because they are more familiar looking. The interesting thing I have learned is Canadian printed charts (now all Print on Demand) are also updated weekly, just as the US ones are, but the Canadian RNC made from these printed charts are much delayed, being at most once a month, and often longer.  They are not updated until the Canadian Light List is updated, which is on a monthly schedule, but often delayed as noted above. Thus they hold off on updating the RNC until the Light List is issued.

Put another way, with Canadian charts we have the unusual circumstance where the printed chart could be up to a month or more newer than the RNC that represents it, which is one more argument to have both the ENC and the RNC. Not only does the ENC sometimes add data to the description of the aids, it is almost certainly up to date if latest chart has been installed (which is not the case for the RNC).

Latest chart editions
To be sure you have the latest chart editions at departure, you can download these pdf files. For the US, we can assume that all formats are updated at the same time; for Canadian charts as noted above the printed charts can be earlier than the echarts.

            US Charts Dates of Latest Editions

            Canadian Charts Dates of Latest Editions


For an extended discussion of how to use the Light List see Inland and Coastal Navigation. The Light List is structured in a unique way, separating main waterways and secondary, and sometimes a light on the corner of these is tricky to find if we do not know its name, or it does not have a name. What we do know is, all lights and buoys are in there, somewhere, and each has a unique number.

A special thanks to the Canadian Department of Fisheries and Oceans, CHS, NOTMAR Division in Victoria for their useful information on details of charting and chart publication.

Navigation Lights—The R2AK Short Course

No matter how sophisticated our navigation electronics might be, safe navigation at night boils down to keeping track visually of where you are relative to navigation lights—on buoys, lighthouses, or posts in the water.

Recall that the lookout, Maureen Jones, warned the third mate in charge of the Exxon Valdez that the crucial Bligh Reef Light was on the wrong side of the bow as they sailed forward, onto the rocks. In fact she warned him twice. [*]

Efficiency is also at stake when you have limited navigation aids on the boat or aids to navigation on the waterway. You might turn into the wrong channel or miss the one you want  if you misjudge when certain lights should or should not be visible.

We have more in-depth treatments of this important topic in the book Inland and Coastal Navigation, but we present here the short version that we prepared for the R2AK team for a quick review, which accounts for examples from Canadian waters.

Define the terms.

Visible range (VR) is how far off in nautical miles you can see the light from your elevation.

Nominal range (NR) is the brightness of the light expressed as how far you can see it in nautical miles when the atmospheric visibility is 10 nmi

Geographic range (GR)  is how close to the light in nautical miles you must be for it to be over the horizon, as viewed from your specific elevation above the water

Luminous range (LR) is the effective nominal range when the atmospheric visibility is not 10 nmi.

h = our height in feet above the water level.

H = charted height (ft) of the light above MHW… not often do navigators account for tides in these computations but in extreme cases they could dominate the answer.

Figure the values

• VR is the smaller of GR and NR to the light.  We can look up NR, but we must compute GR as it depends on h and H.

• NR is on the chart, or failing that we find it in the Light List, which is available for US and Canadian waters in pdf format. US Light List for AKCanadian Light List for Pacific Coast (need several parts)... doesn't every navigator want to have the Light List in their phone?

• GR (nmi) = SQRT (h) + SQRT (H).  

GR Notes.  There are tables in the Light List that list GR for various values of height, from which you find the value for you and for the light and add them, but the height steps are generally too large to be useful for small craft. Sample at the end here.

The CND Light List has a nomogram to determine GR based on h and H, but again, this is an easy computation for better results.  Both of these solutions are presented at the end here, but a phone calculator is best solution.  Sample at the end here.

Also, when comparing those published solutions you will note that our formula gives a smaller value, i.e. the official solution has a factor of 1.17 in front of it, so our GR is 17% shorter.  Our value is easier to remember and usually more accurate. The slightest chop on the water will reduce this value by that much, not to mention that the entire analysis is not better than ±10% or so, not even counting the effect of Luminous range. On the other hand, omitting the effect of tide can have a large error for cases where H is relatively low (under say 50 ft) and the tide range is large (over 10 ft or so). Refer to the "long course" notes for sorting that out.


Assume your h = 9 ft, so GR will always be SQRT (H) + 3 nmi.  A light that is 25 ft high has a GR = SQRT (25) + 3 = 8 nmi.

If the NR to light in question is 6 nmi, then you will not see it till you are within 6 nmi.  In other words, the light is well over the horizon (on a clear day with binoculars you might be able to see the lighthouse in daylight), but the light is not bright enough to see it at night till you get to 6 mi off.

On the other hand, if the NR is 13 nmi, then you will not see it till you are within 8 nmi.  That is, it is shining out into space a distance of 13 nmi, but is below the horizon till you are within 8 nmi of the light.

From the book Inland and Coastal Navigation

Look up the NR form chart of Light List; then compute the GR from h and H, and then VR (when you see the light), will be the smaller of the two.  You will see it closer than this visible range, but not farther.  Your h is not always constant, depending on your boat.

You can look from the cockpit, or from the deck, or from standing on the boom, etc. It is beyond this “short course” to investigate what it means when you see the light standing on the boom, then jump back in the cockpit to tell your mates, and you can no longer see it. Back up on the boom, and it is there again. Hint: it is called bobbing a light.

Example 1

Lights in question viewed on Canadian RNC #

Light on Lasqueti is only described as "FL," meaning flashing.  (See page 33 of the AK Light List for the definitions of characteristics, shown later here.)

With no color given we can usually assume white.  But to figure how close we have to be to see this takes more work because we do not know how high or bright it is from the chart, i.e. we do not know GR or NR from the chart in this case.

Go to Canadian Light List, sample below.  If you search or check the Index on Lasqueti  you will not find it, which is a good exercise in this business.  So we have to guess a name, i.e. try looking under “Prowse,” and that finds it, and now you know the name of that light is False Bay Light.  The beauty of the pdf version is it searches better than an print index.  There you will see this:

From the Canadian Light List

We see for this light (using h = 9 ft… i.e. a sailor standing on the deck of M32x on the way to Ketchikan)!

GR =  3 + SQRT(5.5 * 3.28 ) = 3 + SQRT(18) = 3 + 4.3 = 7.3 nmi, or

GR = 7.3 nmi

Note our formula uses feet, but the Canadian tables are in meters, which accounts for the 3.28 factor.  A little practice with a cell phone calculator makes this very fast.

The NR of this light is listed as 5 nmi, i.e.

NR = 5.0 nmi,

which is smaller than the GR, so the VR of this light is limited by its brightness;  you will not see it till you are some 5 mi off.   These are ±10% type numbers, maybe ± 15%.

Answer:  Visible range = 5 nmi.

Now you can go on the chart, but a waypoint at that light, and then a range ring on that waypoint with radius of 5 nmi to show clearly when you will see it.  This is illustrated in the video below.

Example 2.

We also see Sisters Is light in the raster chart (RNC) above marked as:  Fl (2) 15s 21m 21 M.   In the Light List we learn that this group flashing light has a period of 15s, same as on the chart, meaning that is how long it takes the pattern to repeat, not the time between flashes  This would imply the light is 21 m high (69 ft) with nominal range of 21 nmi. 

However, it appears that this latest version of the Canadian raster chart (RNC) is not correct.  We have to assume the Light List is correct. It says 24.3 m high = 80 ft, with a nominal range of 16, not 18.  That is the virtue of the Light List. Refer to the Truth Meter at the end here.

Note that the latest official Canadian vector chart (ENC) shown below has it right, or at least consistent with the Light List.

Lights in question viewed on Canadian ENC #

It is much easier for an agency on a budget to keep the vector charts (ENC) updated compared to the RNC, which are copies of the printed charts.  We compare these to the latest Navionics charts below.

This vector chart, however,  has the False Bay NR wrong, i.e. shows 6 but Light List says 5. Back to the Truth Meter.

So for Sisters Is. Light  GR= 3 nmi + SQRT(80) = about 12 nmi.  Its NR = 16, so in this case the visibility of this light is limited by our low perspective.  For most small boats looking at bright lights it will be the GR that is the limitation.

Answer: VR =  12 nmi.

Below shows how me might plot these on a paper or echart to keep track of VR.

The red circle shows range of False Bay Light; blue circle is range to Sisters Is Light. So we should see Sisters Is Light not far  beyond the Ballenas Is waypoint, headed NW, and if the route ended up along the southern shore, you would not see the False Bay Light at all. The faint colored lines are the tracks of a few boats from the 2015 R2AK.

End of Lesson. To follow are a few background pics.

*   *   *

Here is a table of light characteristics from the  US Light List.

And here is a table of GR values from the US Light List
The notes above propose computing directly, but some navigators (in more comfortable conditions than on an M32x) might prefer to just have this table handy and use it.
Here is the Canadian solution to the GR computation, but this definitely requires a nav station.

Here are the displays of these lights in the Navionics app called Boating US and Canada, which is quite a good bargain and the charts seem pretty good. It sells for $16, whereas the full set of Canadian echarts that can be run in any echart program costs $199 each for RNC and ENC. Rose Point has a nice set for $99 each that run in Coastal Explorer. For this race we made the routes in Coastal Explorer and then transferred them to both the Garmin 78s and the Navionics App... both of these processes takes some hokey pokey that I will write up in the near future.

Lights in question viewed in Navionics charts (PAC493). The pictures  are out of order. Sisters should be shown on the left. The team used two Android phones and one iPhone 6

The only thing left to add is the "Truth meter" table that compares dates of all these resources, which agree fairly well, but not precisely.

coming soon...

[*] It is not clear if this fundamental observation was early enough to have prevented the grounding had he responded to her first alert, or if maybe had they all looked more closely to lights on the horizon earlier it might have been prevented, but it was indeed awareness of where the light should be by one person that told everyone they were in trouble.

She was sailing as an AB, but actually had a Third Mate License of her own. These notes are from published testimony. I have no special knowledge of this incident nor of the the people involved.

Saturday, July 2, 2016

Using Polarized Sun Glasses as a Viking Sunstone

This note is an annotated, illustrated version of a Chapter 8 section of the book Emergency Navigation, called Finding the Sun as a Viking Would. This note comes to be written now because we had made a (cryptic) Youtube video on this topic some years ago for the students of our online course in emergency navigation, and frankly it was not very clear what was going on in the video without the background of the course or that book.  But the video gained some attention and several commenters ask for clarification, so this is an attempt to do that. It is frankly a pretty neat technique, so I can appreciate the frustration of not knowing what was going on in the video.  Something seemed to be working (according to the narrator, me), but it was not obvious what!


Leif Karlsen, in his book Secrets of the Viking Navigators, gives a good argument that the Vikings used crystals of Iceland spar to find the direction of the sun when just below the horizon or when obscured by fogbanks on the horizon, common at latitude 60° N where they did much of their ocean sailing. The technique he proposes works very well. We have done it many times using these Viking sunstones, which are readily available from gem shops online (you need a clear crystal, 1 to 2 inches on a side). This technique can pinpoint the direction to the sun to within a few degrees, and it was in fact used for many years in a more sophisticated arrangement as the basis of the Kollsman Sky Compass in the early days of polar exploration by air.  Leif’s original instrument is still on display and the Nordic Heritage Museum, just around the corner from Starpath HQ. I had the pleasure of working with Leif on the project for many years. His study is the definitive work on the most likely way the device was actually used in Viking times, but we had to publish a special peer-reviewed article to confirm his right to this claim.

You can simulate the sunstone method with about the same precision using any polarized film, such as the lenses of  polarized sunglasses or some polarized camera filters. Some older sextant models also have polarized filters on the sunshades.

In addition to that, you need a small piece of cellophane. Many clear packaging tapes, the transparent windows of a CD sleeve, or the protective packaging of many products are often cellophane. On the other hand, some clear plastic products that look like cellophane, are actually another type of plastic and will not work for this application.

To prepare the lens, attach a piece of cellophane diagonally across the lens as shown in the left inset in the graphic below. Look through the lens with the cellophane on the far side (sky side) of the lens. The lines with the arrowheads in the figure represent the edge of the cellophane, crossing the middle of the lens.  

Figure 8-4 from Emergency Navigation. The bottom left inset shows a cellophane tape on the glasses; the bottom right inset shows the direction to look. The top part shows 3 examples of applying this technique.  The middle one is what you see when looking in the right direction. The three images of that group would be on top of each other when actually yawing the orientation to the right and left of the true sun direction.   The groups on either side of that show what it looks like if you are not quite looking in the right direction when you yaw the device to the right and left.  You still find the direction to the sun, but it is not as easy to locate that on the horizon.   Start by looking in the direction that is opposite to your best guess of the sun’s bearing. You will not know exactly where to look, as that is what you are trying to discover. Once facing that best-guess direction away from the sun, angle your view up from the horizon by an amount that you estimate would put you about 90° from the line straight to the sun. Referring to the right inset, if you point to where you think the sun is, your thumb will point in the best direction to start looking for maximum polarization. If the sun is just on or below the horizon, you would look straight up. If the sun is about 30° above the horizon, you would look in the opposite direction at about 60° above the horizon.

In the video example, we used inexpensive polarized sunglasses that had no frame at all (Bartells in Ballard), it was just one piece of plastic formed into glasses. The we just cut them in half.  I think we used the clear packing tape we get from U-line, and taped a strip across the glass diagonally as shown.

Then you want to hold this up and look at the sky through the glasses and tape (tape on the opposite side you are looking at), but you do not look in the direction you think the sun is—even without seeing it (already set or obscured) you know very roughly the direction to the sun. Rather, you want to hold this up in the direction that is 90º from that direction. In other words, it the sun had just set (roughly the case in the video), then you would be holding this up, looking directly overhead. For cases when the sun is overcast or behind clouds but not near the horizon, then you would look in a direction opposite to the sun at an angle from the sun as illustrated in the picture.

An important requirement is that this direction you are looking, i.e. 90º from the estimated sun direction, has to have some clear sky. If you look 90º from the sun and it too is covered by clouds, this will not work.  Thee can be some level of overcast, but there must be some level of clear sky in that direction.  The closer you are to looking at 90º to the actual sun, and the clearer the sky is in that direction, the better it will work.

The three center group of drawings in the picture above show what you will see when you are facing the proper direction of maximum polarization, directly opposite the true bearing to the sun. When the cellophane edge is perpendicular to the horizon, the lens will be the same shade on both sides (cellophane side and no-cellophane side). When you rotate it slightly to the right and left (that is a yawing motion), the sides will change brightness, as shown in the two figures adjacent to the center one.  There are three groups of pictures here, we are talking now about the middle group, which is what you see when you are looking in the proper direction.

The two rotated views are shown to the right and left (in the center group), but they would actually be in the same position as the middle one, just rotated to the right or to the left. The video will illustrate what we actually see.

On the other hand, if you are not facing opposite the true direction to the sun, you will see what is shown on the right or left of the center figures. If you are facing to the right, the edge of the cellophane will lean right when the sides have the same brightness, as shown, and when facing to the left of the proper direction, you will see what is shown on the left.

In short you can find the direction to the sun even when pointed slightly wrong, but you will not get a good vertical line as shown in the middle group, which takes more judgement on locating the bearing on the horizon.

This is a subtle process that takes some practice… and patience. But once the procedure is grasped, it can then be repeated much more readily. The sequence is: Look in the approximate right direction and then in the approximate right elevation. Then, starting with the cellophane edge perpendicular to horizon, rotate the lens to find the orientation of that edge line when the two sides are about the same brightness. When you are in about the right direction, the two sides will switch in brightness quite prominently—providing you do indeed have a polarized filter and true.

I have always found when using the sunstone or these glasses in a hand held mode—as opposed to the device Leif invented for using a mirror—that it is easier and more accurate to hold a ruler along side the crystal or in this case the polarized glasses. The ruler enhances your perception of the yawing motion for better precision.  Also in the video I also used a mirror.  I just held the ruler and glasses up in one hand overhead and looked at it with a mirror in my lap. These modifications are (very crudely) sketched in the pictures below. (I will improve these when we can.) Also shown below is an illustration of the right direction to look.

You can try both methods to see what works best for you. Just looking up works fine and is likely best. We used the mirror just so someone could make the video.

Here is the video showing an actual measurement.  The screen caps preceding it below show what is meant by "right" and "wrong" heard in the video. 

Here is the explanation that is printed in the video description:

This is just after sunset, with a bright patch on the horizon to locate sun direction as a test. It is using a mirror facing straight up to view the glasses that have a piece of cellophane tape pasted diagonally across the glass. This can be done without the mirror by looking straight up to the taped glasses, but i could not take a video of it that way. The video was taken with an iPhone.

This is a modern version of using polarized film (cheap clip-on sunglasses, cut in half) as a Viking sun stone (Icelandic Spar). It is a way to find the direction to the sun after it has set or when it might be behind a cloud bank. Maximum polarization is in a direction 90º from the sun direction, which is straight up with the sun near the horizon.

I am holding a meter stick along the edge of the cellophane tape to enhance the rotation angle, which helps pinpoint the direction.

When you watch the video, I am rotating the ruler and glasses to the right and left and noting which side is dark or light, and when the two sides are the same brightness, the the edge of the cellophane and in this case ruler are pointing to the sun... which was set below the horizon for some period of time as i was doing this.  I was using a mirror in this case only so i could make the video, which would he hard to to looking up. In this case a friend was taking the video over my shoulder looking down at the mirror. Doing this on your own there is no need for a mirror. It just gets in the way.  By the way, the obvious way to practice is do it (without a mirror as you can then see where you are pointed, and do it just at or after sunset so you know indeed what is the right answer.

Too far right. One side is darker than the other.

Just right, both sides same color. The Ruler is pointed to the sun, even though the sun is not viable at the moment. It could be set (as in this case) or obscured behind a fogbank or clouds.

Too far Left. One side is darker than the other.
 ----------------------------------------------- Here is the video -----------------------------------------------

A couple details  (my guess is, no one wants more details at this point!)
This technique works because scattered sunlight is polarized. If you imagine a line straight up to your zenith and another line straight toward the sun, then these two lines define a plane. The electromagnetic oscillations within sunlight that have been scattered by air molecules are perpendicular to that plane, whereas in direct sunlight these oscillations are randomly distributed in all directions. Sunlight that has been reflected from a surface (glare from the water, for example) is also polarized, which is the motivation for polarized sunglasses. This light is horizontally polarized parallel to the reflecting surface, which means that sunglasses designed to block this glare are vertically polarized. An easy way to test that a pair of glasses is polarized is simply to look at such a reflective glare and rotate the glasses (looking straight through the lenses to the glare, roll the lenses, without pitch or yaw), and you should see the intensity of the glare change quite noticeably. On land you can do the same with bright glare from a window or car hood or bumper. When the glasses are working properly, you can see though the glare-producing windshield into the car; without them, or with your head turned 90°, you see only glare.

If you are using a lens of a pair of sunglasses, chances are the polarization axis is parallel to the bottom of the glasses, which means you will find the brightest or darkest light transmission with the lens parallel or perpendicular to the horizon. If  this is not the case, find the best orientation and draw a line across the bottom of the lens when rotated into the darkest or brightest orientation—or mark the horizon with a piece of tape if you don’t have the right pen for the job.

When you attach the cellophane it should go diagonally across that axis.  Once you have this "polarization compass" assembled, look again to the correct direction and rotate the device. You will notice now that the right and left sides alternate in brightness; when the two sides have the same level of brightness, the edge of the cellophane is pointing to the sun. The trick is to hunt around for the best direction; rotate the compass, note the sharpness, turn left a bit, try again, turn right and try again. When the angle is optimum, look up a bit and then down, etc.

As shown in Figure 8-4, you are finding a great-circle arc that points to the sun, so when looking to the left of the proper vertical plane, the line will point right, and when looking to the right of it, the line will point left.

Once you find it with access to clear sky at 90º, the location of the brightness transition becomes very sharp. In short, this really works well.


Final note.
After coming back to this video because of the several notifications we were getting here, I looked around at other videos online about the use of the sunstone itself.  There are quite a few. They vary from almost right, to totally bizarre.  I will try to get help and make a quick video of how to use an actual sunstone for this purpose.  It is easier than this.