Get GPS distance between coordinates.

[dtorrent]

Hello

I'm looking for a proven code to get gps distance between two coordinates. I'm using some code for this but sometimes doesn't work. Let me explain.

In my application I get a list of interesting locations near to me. The problem is sometimes the list I get seems to be correct but sometimes I get some locations that are kiliometers away and I know in the list some near locations are missing.

I don't know why the code I use sometimes is running, sometimes not. I would like to try with another code and compare the results. I don't have here the code I using, I will post it later.

Thanks

David

[dtorrent]

I'm thinking about it and correct me if I'm wrong but, could be that when I'm getting the right list is because I'm using the GPS coordinates and when I'm getting the 'bad' list is because I'm in the office (for example ) and I'm getting my localization via gsm antenna?

David

[wizard_hu_]

If you are interested about local things only, I think a simple Euclidean distance calculated on latitude and longitude is adequate enough.
When there are interference/delay/reflections because you are inside a building, it is more likely that you get false readings from the GPS itself, that is why the vicinity list seems to be calculated for an other location. Because it is really calculated for an other location.

[devfish]

The formula you are looking for is called "great circle distance". There's a javascript version of it here ( http://www.movable-type.co.uk/scripts/latlong.html ) which would be pretty easy to translate to .NET . Let me know if you need some help translating it to C# or VB.

[mahbub_s60]

Have you checked this?
http://www.developer.nokia.com/Commu..._two_landmarks

You are doing application for windows phone?

[symbianyucca]

What about using actual API: http://msdn.microsoft.com/en-us/libr...=VS.92%29.aspx check the function GetDistanceTo

[hclchd]

i think the diff of longitude and lattitude will give radial distance it would be better if actual api is used or try updating map database

[dtorrent]

Thanks for your answers

Yes, I'm developing for Windows Phone and I knew about the GetDistanceTo but I'm not using it. Could be for some reason that I don't remember now but I'll check it again, thanks!

[kangaderoo]

It all depends a bit on the distance between the points.
The halfsine and cosine functions use a constant average (6371000.0m) for the earth radius, and give a good approximation over (very) long distances.
Depending on your location on the globe the number of meters per degree (lat long) is not constant.
That's where datum conversions (UTM) comes in handy.
For smaller distances, where all points are in the same UTM zone, I would convert all (lat long) into easting/northings, and use Pythagoras' theorem to calculate both the distance and the bearing.

[michalj]

Hi,

You can try to use my code.

I have placed it sometime ago on my blog - link to distance between two GPS points

I hope it will be useful for you.

Best regards,
Michał

[dtorrent]

Thanks for your link, I'm going to check it next week.