Question

Given two gps coordinates the length difference can be calculated by using the haversine formula. But what about the other way around:

• Compute the length difference in meter for a given Lat/Long double

• Compute the Lat/Long double for a given length in meters

I know this is not exactly possible since it differs from the point on the earth you are, but is it possible to approximate this or something similiar? This does not have to be very precise.

Answer 1

If your displacements aren’t too great (less than a few KM), use the quick and dirty estimate that 111,111 meters in the y direction is 1 degree (of latitude) and 111,111 * cos(latitude) meters in the x direction is 1 degree (of longitude).

Alternatively:

//Position, decimal degrees
 lat = 51.0
 lon = 0.0

 //Earth’s radius, sphere
 R=6378137

 //offsets in meters
 distanceNorth = 100
 distanceEast = 100

 //Coordinate offsets in radians
 dLat = distanceNorth/R
 dLon = distanceEast/(R*Cos(Pi*lat/180))

 //OffsetPosition, decimal degrees
 latO = lat + dLat * 180/Pi
 lonO = lon + dLon * 180/Pi 
This should return:

 latO = 51,00089832
 lonO = 0,001427437