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» Online Classroom   » Tech Support   » Barometers   » ALL — Finding your elevation

   
Author Topic: ALL — Finding your elevation
David Burch


 - posted December 19, 2005 12:45 AM      Profile for David Burch           Edit/Delete Post 
In some barometer reading exercises you may want to know your elevation. One way to get that is from a topo map. Here is an example using the fine resource of www.topozone.com. There are likely other sources as well.

Use your lat/lon or street address to find the right map, then somehow figure out what the contours mean. In the sample here, they are shown every 5 meters, and you can see that Starpath HQ is located about halfway between 50m and 45m, so we call it 47.5 m and then 3.28 ft per meter gives us a ground elevation of about 156 ft. The main office floor is about 2 ft above that, and the barometer on our shelf is about 5 feet above that, so we use 163 ft as a check for absolute pressures, when we care to... though as explained elsewhere, we generally offset our barometers to read sea level pressure directly, which is easy to set as explained.

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Another method is to use Google Earth ( See Vol 18 of Starpath Newsletter), you can simply put your cursor on your house and read off the elevation. We have just done this one comparison, but it is certainly easy.

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Here we have the cursor just outside of our front door. The topo map gave 156 ft, the Google Earth data datum is 173 ft, which is reasonably consistent -- from the top of the picture to the bottom is a change of about 15 ft.

This method is super convenient if you have a new computer (see notes in the link above). It does not work well or at all on older computers.

Please let us know your results if you make a test of your own and we will post them here.

From: Starpath, Seattle, WA
David Burch


 - posted June 09, 2009 12:31 AM      Profile for David Burch           Edit/Delete Post 
You can now get very accurate elevation at
www.starpath.com/barometers.

Remember to enter a very precise lat-lon if you want a precise elevation... ie one side of a street is not the same as the other side.

From: Starpath, Seattle, WA


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