Friday, December 27, 2013

Google Earth as an Aid to Chart Reading

We have an exercise in our online course on navigation that asks students to choose useful bearing targets when heading east along the south side of the Strait of Juan de Fuca, just passing Freshwater Bay. We have students from all over the world, and most do not know the area. This is not a problem, because we are focusing on chart reading, and that is the same worldwide. Skills you learn from one chart are usually easily transferred to other charts, in other parts of the world.

With that said, there are nuances to chart reading, and sometimes the terrain may be more complex than might appear from a chart. Also some cryptic notes on the chart or in Coast Pilot may not be clear till seen in person.

Thus enters Google Earth, which does indeed let us see coast lines around the world. Here is the example at hand. Below is the chart of Freshwater Bay, and in the background we see two mounts clearly marked. These were part of an answer to our practice question, so we add this new dimension to that answer.

Now turn to Google Earth and find this location (you can type in a lat lon, as one way), and you will get after some zooming, rotating, panning, etc the following view of the bay... looking south from over the water.

The round spit on the left is Angeles Point, which by the way is where the USCG defines the limit of mariner's sea time between coastal and inland. Every mile you log west of there is coastal time; east of there it is inland time.  It is a bit arbitrary.

We can now use Google Earth to look up from here, from a lower perspective. This one is more from a plane than a boat.

Now we begin to see more or less what you would from the water, but it still might be difficult to find the two mounds we are looking for.  So me must get out the binoculars, which we do on Google Earth by holding the shift key and moving the mouse up the screen.

This works very well, but not quite as good as we might hope for.  The two peaks that are charted are there because they are indeed more prominent than shows here.  The graphics cannot quite match the actual shading that is seen in life.  The background behind these would be notably darker so the peaks stood out.

Below is the areal view with push pins set at the lat lon of the two mounds, that shows a bit better why these show up more distinct from the water.

To have more fun with GE, you can also travel inland and look back out the river valley that these mark, as shown below, looking north.

If you have not played with GE in this manner, you might give it a try. It takes a bit of tweaking and practice. You might want to go to Settings (Preferences) and choose the option to exaggerate the vertical scale, and of course have 3D turned on.  I find it works best using a mouse than a touch pad.

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