Thread: Stuck converting Java code

It might me better if you base your code on this Source: Arc and distance between two points on Earth surface

Unlike Java, the modulus operator only works with integer types in C.

Also, see abs vs fabs.

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)