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USGS Elevation Query Web Service Method

Posted on 2012-04-10
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Last Modified: 2013-11-19
I am trying to use the USGS Elevation Query Web Service Method to retrieve elevation (MSL) for a point specified by geographic coordinates ( latitude and longitude).
The documentation page at USGS doesn't make any sense to me. I can't figure out how to pass the parameters to the method in a url.
http://gisdata.usgs.gov/XMLWebServices/TNM_Elevation_Service_Methods.php#

I see that I need to pass X_Value and Y_Value (lat & lng) to the method using
http://cumulus.cr.usgs.gov/XMLWebServices/TNM_Elevation_Service.asmx?op=getElevation

But, I can't find a way to specify the parameters.

This looks to me like it should be a simple thing to do if I only knew the syntax of the query.
I am awarding 200 points based on this assumption. If someone points out to me that this is a more complex problem than it looks like to me, I will increase the points accordingly.
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Question by:Cal_George
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Ray Paseur earned 200 total points
ID: 37832001
See the "HTTP GET" example on this page.  I am not sure this will work, but it's at least got an example of how to call the web service.
http://gisdata.usgs.gov/xmlwebservices2/elevation_service.asmx?op=getElevation
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by:Cal_George
ID: 37834407
Thanks Ray,
I saw that link on the page from my original post too. But, your response got me thinking about it a little deeper. I viewed the source on that page and found the parms that it posts before invoking the action.

I think I can post those values and use a submit button to return the xml result.

It would be nice to be able to see what proc is called from
gisdata.usgs.gov/xmlwebservices2/elevation_service.asmx/getElevation

I am actually trying to determine if two locations (potential radio sites) can see each other.

What I am actually trying to do is determine multiple points along a path or course. I can then compare those elevations to the radius of the Fresnel zone to determine line-of-sight between the two points.

Currently, I can derive elevation of the two points. I can calculate the true course and distance between the points. I believe I have even found a formula to determine the geographic coordinates along the course.

I am not sure that I can come up with a way to query multiple points along the path without user interaction every 100 to 200 feet along the way.
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by:Cal_George
ID: 37834437
OK, Ray,
You got me on that one. I didn't scroll down far enough.
There is a clear example on that page in a font that is so small I had to blow it up 5 times to be able to read it.
Good solution. I should  have gotten this without submitting the question. Maybe someone else will stumble into this thread when it really matters to them.
Cheers,
George
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Author Closing Comment

by:Cal_George
ID: 37834443
Good answer.  This will do the trick.
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