I used the USATF New England Association Office for this example. Google Earth says the decimal coordinates are latitude 42.335895° and longitude -71.149826°.
I went to the USGS Elevation Service web page.
http://cumulus.cr.usgs.gov/XML...asmx?op=getElevation
I was prompted for several values....
X_Value (Longitude): -71.149826
Y_Value (Latitude): 42.335895
Elevation Units (feet or meters): meters
Source_Layer: NED.CONUS_NED
Click on the image to enlarge.
It will return an XML file containing the elevation of 32.7786979675293 meters.
<USGS_Elevation_Web_Service_Query>
<Elevation_Query x="-71.149826" y="42.335895">
<Data_Source>NED 1 arc-second: Contiguous United States</Data_Source>
<Data_ID>NED.CONUS_NED</Data_ID>
<Elevation>32.7786979675293</Elevation>
<Units>METERS</Units>
</Elevation_Query>
</USGS_Elevation_Web_Service_Query>
Click on the image to enlarge.
You can experiment with the values. Try entering -1 as the Source_Layer and -1 as the Elevation_Only values. The data source will change from a 1-arc second to 1/3-arc second source.
The elevation has 13 decimal places. I cannot imagine an elevation that accurate (1 micron is 1 x 10^-6 meters), but it may be a useful resource.
Google Earth said the elevation at those coordinates is 32 meters.
Thank you. -- Justin
ps. I stumbled on an iPhone Elevation App that makes use of the USGS Elevation Service.
Click on the image to see more.