# [gdal-dev] Geodetic Problem

David Baker (Geoscience) david.m.baker at chk.com
Tue Mar 16 16:31:33 EDT 2010

```Frank and the List,

I have a geodetic problem I hope GDAL/OGR can solve.

The setup:

I have two radio towers each the same height and at the same elevation being 10,000 meters apart.  I know the latitude and longitude of the first tower and those coordinates reference WGS84 (though they could be any geographic CRS, NAD27, NAD83, etc.).  I also now the baring to the second from the first measured from true north at the first tower.

The problem:

Given the above information and using the prebuilt tools, GDAL/OGR utilities, what workflow would one use to calculate the latitude and longitude of the second tower?

The hints I have gotten so far say to use a conformal projection (UTM maybe?) centered at the first point with a scale factor of 1, a local projection.  Calculate the Cartesian offsets from the first point to the second based on the azimuth of the given baring.  Using the baring calculate the x and y offsets to the second point and use offsets to find the x and y of the second point in the local coordinate system.  Then, reproject the x and y of the second point to the latitude and longitude in the CRS of the first points latitude and longitude.  If this is correct, I guess the question is, what would the proj4 parameters be for such a local projections.

Thanks,
David

David M. Baker
Senior Geologist - Chief Technology Advisor
Chesapeake Energy Corporation
405-935-3715 office
405-496-5373 cell
david.m.baker at chk.com<mailto:david.m.baker at chk.com>

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