Stuck converting Java code

This is a discussion on Stuck converting Java code within the C Programming forums, part of the General Programming Boards category; Hi Guys, I'm trying to port the destination formula from here: Calculate distance and bearing between two Latitude/Longitude points using ...

  1. #1
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    Stuck converting Java code

    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.

  2. #2
    TEIAM - problem solved
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    It might me better if you base your code on this Source: Arc and distance between two points on Earth surface
    Fact - Beethoven wrote his first symphony in C

  3. #3
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    Unlike Java, the modulus operator only works with integer types in C.

    Also, see abs vs fabs.
    Last edited by Tclausex; 02-28-2013 at 06:58 PM.

  4. #4
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    Quote Originally Posted by Click_here View Post
    It might me better if you base your code on this Source: Arc and distance between two points on Earth surface
    This one takes distance, heading, and one one coordinate pair,
    and outputs a coordinate pair for destination.
    I can calculate distance between two points with Haversine already.
    This one is for drawing the ruler on a GPS screen,
    and the accuracy circle around the dot that marks the user's position.

  5. #5
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    I got it with this tutorial:
    Bearing and Distance Calculator Calculation Methods
    The guts of it are already in C, and you can leave out the
    bearing calculations if you just want the point coordinates.

  6. #6
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    instead of %, check out fmod

  7. #7
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    Quote Originally Posted by xArt View Post
    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)
    I'm the author of MiniBasic: How to write a script interpreter and Basic Algorithms
    Visit my website for lots of associated C programming resources.
    http://www.malcolmmclean.site11.com/www

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