Thursday, February 27, 2020

Obtaining Buoy Data by Email for the Model Accuracy App.

Model Accuracy is a unique program that allows navigators to compare their logged wind and pressure data over a recent past period with one or more model predictions in order to evaluate the model. For typical use underway, the computer does not need to be online (via satcom), because the grib files and wind data are already stored on the computer.

The program also offers a way to compare the models to buoy data, and indeed when the computer is connected to the internet, it has a super convenient way to download the buoy data to make the model comparison. Underway, however, this link does not work unless the user has set up a rather complex interface from program to satcom.

What we want to show here, however, is we can get the needed buoy data underway from Saildocs so that this powerful function of the program is still active underway.

The program needs to have the model GRIB data in one folder (say, MyGribs) and the logged observations or buoy data in another folder, say MyData.


Step 0.  
For this method it is best to record some information ahead of time about the buoys you will want to use. Go to NDBC for your buoy of choice and record the lat, lon, and height of anemometer in meters. In this example using buoy 41010 we get:

28.878 N 78.485 W (28°52'39" N 78°29'6" W)
Site elevation: sea level
Air temp height: 3.7 m above site elevation
Anemometer height: 4.1 m above site elevation

Rewrite the red part as:

28.878 -78.485 4.1 

(in decimal lat-lon, w lon is negative). We will use this later.

If you did not get this info ahead of time, then send this query to saildocs:
and you will get back the latest report, which includes the Lat, Lon of the buoy that we need. Then just assume that the height is 4.0 m.  Most are 3.5 to 5.0

Step 1.
To get the data: send email to, with this single-line, plain-text message


For two buoys use two lines same but for buoy number.

You will get back a long text file, one for each request, whose top part will look like:

Step 2.
Select the data part leaving off Saildocs headers and footers, then save to a text file and change to courier font to see something like this

Step 3.  
From your records of the buoy data at NDBC, insert at the top left the lat-lon and anemometer height in meters as shown below and then change the file name to


This is buoy number_yyyymmdd_hhmm.noaa.txt, where the hhmm is the UTC that you downloaded the buoy data. It will be in the Saildocs header.

So it now looks like:

Step 4.
Save this file into your MyData folder and carry on with Model Accuracy as if you had fetched the data online.

1 comment:

Unknown said...

Very nice checklist! Thank you for sharing this!