Calculating Terminal Co-ordiantes

[scruffyduck]

I have a program which needs to determine the co-ordinates of a point at a given distance and bearing from the user aircraft. I have a routine which does it up to a point and works tolderably well at low latitudes.

I am sure there is a better algorithm out there like the one to calculate the distance and bearing between two points but I have not found it yet.

Would be most appreciative it anyone can point me in the right direction. There are a couple of websites which do it but do not say how :?

[Pete Dowson]

I have a program which needs to determine the co-ordinates of a point at a given distance and bearing from the user aircraft. I have a routine which does it up to a point and works tolderably well at low latitudes.

I am sure there is a better algorithm out there like the one to calculate the distance and bearing between two points but I have not found it yet.

Not sure how the altitude comes into it -- you should be measuring from the latitude and longitude, the point on the Earth directly below the aircraft.

For accurate measurements over long distances you need to use spherical trig and assume great circle routing. Try Googling on "great circle calculation" or similar. For example, I came up immediately with the following reference:

http://www.meridianworlddata.com/Distance-Calculation.asp

This, like most others you'll find, is based on finding the distance given two known points, so you would have to invert some of the computations to derive one point from the other given distance and bearing.

And don't forget to use true north for the bearing! ;-)

Regards,

Pete

[scruffyduck]

Thanks Pete - I think I did say latitude not altitude :D :D