Originally Posted by

**xArt**
Hi Guys,

I'm trying to port the destination formula from here:

Calculate distance and bearing between two Latitude/Longitude points using Haversine formula in JavaScript
So far, I have this:

Code:

int brng;
brng = 90;
float lat1 = GPSlat;
float lon1 = GPSlon;
float lat2;
float lon2;
double dLat = d*cos(brng);
lat2 = lat1 + dLat;
double dPhi = log(tan(lat2/2+PI/4)/tan(lat1/2+PI/4));
double q = (isfinite(dLat/dPhi)) ? dLat/dPhi : cos(lat1); // E-W line gives dPhi=0
double dLon = d*sin(brng)/q;
// check for some daft bugger going past the pole, normalise latitude if so
if (abs(lat2) > PI/2) lat2 = lat2>0 ? PI-lat2 : -PI-lat2;
lon2 = (lon1+dLon+PI)%(2*PI) - PI;

but the C compiler doesn't like the % sign in the last line.

What is that doing?

Cheers, Art.

Code:

void distandbearing(float lat1, float lon1, float brng, flaot d, float *latout, float *lonout)
{
float lat2;
float lon2;
double dLat;
double dPhi;
double q;
double dLon;
dLat = d*cos(brng);
lat2 = lat1 + dLat;
dPhi = log(tan(lat2/2+PI/4)/tan(lat1/2+PI/4));
q = (isfinite(dLat/dPhi)) ? dLat/dPhi : cos(lat1); // E-W line gives dPhi=0
dLon = d*sin(brng)/q;
// check for some daft bugger going past the pole, normalise latitude if so
if (abs(lat2) > PI/2) lat2 = lat2>0 ? PI-lat2 : -PI-lat2;
lon2 = fmod((lon1+dLon+PI),(2*PI)) - PI;
*latout = lat2;
*lonout = lon2;
}

(Untested)