GIS GeoCoding (Random question)

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Devildog74
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Posts: 719
Joined: 04-Feb-2004
# Posted on: 04-May-2007 07:21:26   

Because there are some really smart people on this forum I figured I would post my question here.

Does anyone know of a formula to find a point that gives the LAT / LON that is X number of miles from the starting point?

Basically, I have a lattitude and longitude in decimal form, like so:

  • <Point> <coordinates>-105.036667,39.836667,0</coordinates> </Point>

Now I need to find the LAT / LON for a point that is X number of miles from my point, and I need to do this for 4 points, each point is North, South, East, and West of the starting point (-105.036667,39.836667).

simmotech
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Posts: 1024
Joined: 01-Feb-2006
# Posted on: 04-May-2007 08:07:08   

Devildog74 wrote:

Because there are some really smart people on this forum I figured I would post my question here.

Does anyone know of a formula to find a point that gives the LAT / LON that is X number of miles from the starting point?

Basically, I have a lattitude and longitude in decimal form, like so:

  • <Point> <coordinates>-105.036667,39.836667,0</coordinates> </Point>

Now I need to find the LAT / LON for a point that is X number of miles from my point, and I need to do this for 4 points, each point is North, South, East, and West of the starting point (-105.036667,39.836667).

This article, http://www.codeproject.com/useritems/Coordinate.asp , might help as it mentions...

Finally you will find a method to calculate distance agains other coordinate. It is implemented using classical Haversine formula (you will find web references inside the code). Result is expressed in meters, the ISO unit for distances. You can add your own code for more calculations.

Not quite what you were looking for but you may be able to work it backwards to achieve what you want.

Cheers Simon

jeffreygg
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Posts: 805
Joined: 26-Oct-2003
# Posted on: 04-May-2007 17:47:53   

You're looking for the Great Circle calculation since we can't use Euclidean geometry to calculate the new location.

Here's an online calculator: http://www.waypoint.org/gps1-calc.html

Hope that helps!

Jeff

Devildog74
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Posts: 719
Joined: 04-Feb-2004
# Posted on: 05-May-2007 00:24:20   

Thanks for the feedback. I am going to opt for the buy option. At my hourly rate I actually make money to buy this API and implement it, and I am really not interested in learning the math (radial geometry) for myself.

Others interested may want to check this out:

http://www.zipcodedownload.com/Products/Family/DistRad/