[gdal-dev] Geodetic Problem
David Baker (Geoscience)
david.m.baker at chk.com
Tue Mar 16 19:25:10 EDT 2010
Thanks for the references... I will look them over. I am correct that the c# binding will not have access to the Geod calc's?
David M. Baker
Senior Geologist - Chief Technology Advisor
Chesapeake Energy Corporation
david.m.baker at chk.com
From: Frank Warmerdam [mailto:warmerdam at pobox.com]
Sent: Tuesday, March 16, 2010 4:13 PM
To: David Baker (Geoscience)
Cc: 'gdal-dev at lists.osgeo.org'
Subject: Re: [gdal-dev] Geodetic Problem
David Baker (Geoscience) wrote:
> 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.
The above will give a pretty good approximation, degrading as the
distance increases. However, the proper way to do this is using
great circle operations. The PROJ.4 "geod" program can do this:
There is more information on geodesic operations at:
I set the clouds in motion - turn up | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
This email (and attachments if any) is intended only for the use of the individual or entity to which it is addressed, and may contain information that is privileged, confidential and exempt from disclosure under applicable law. If the reader of this email is not the intended recipient, or the employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender immediately by return email and destroy all copies of the email (and attachments if any).
More information about the gdal-dev