Bearing calculation out of 2 nmea strings

[ScaleRobotics]

Did anyone ever tried to calculate bearing and distance between
set of 2 cordinates ?

1 fixed (lat, lon), 1 comming in from a GPS NMEA 4800,8N1 GMRC string ?

thansk you

I used the Cordic to get the heading and distance. To get this to work, you need to calculate the difference between the two waypoints

lathome_hi = the 37 part of the 37.12345 degrees
lathome_low = the 0.1234 (as a whole number 1234) part of 37.1234 degrees

This allows you to have a 3 degree difference in distance, or about 180 miles, although you could add some math division to allow further distances.

GPSMath:
    latlow_dif = lathome_low - latdest_low   'find difference in present loc and destination
    lathi_dif = lathome_hi - latdest_hi
    
    lathi_dif = lathi_dif * 10000        'multiply integer degree difference by 10000 
    lat_dif = lathi_dif + latlow_dif     'so we can add decimal degrees to 16 bit number
    
    lonlow_dif = lonhome_low - londest_low
    lonhi_dif = lonhome_hi - londest_hi
    
    lonhi_dif = lonhi_dif * 10000
    lon_dif = lonhi_dif + lonlow_dif    
          
    if west = 0 then toggle lon_dif.15       'inverse negative bit for east europe
    if north = 0 then toggle lat_dif.15      'inverse negative bit for southern hemisphere
    quadrant = 1   'if lat_dif.15 = 1 and lon_dif.15 = 0 then quadrant =1
    if lat_dif.15 = 0 and lon_dif.15 = 0 then quadrant =2  'see which results are negative
    if lat_dif.15 = 0 and lon_dif.15 = 1 then quadrant =3
    if lat_dif.15 = 1 and lon_dif.15 = 1 then quadrant =4
    if north = 0 then toggle lat_dif.15      'get rid of falsing for S hem so we can do math
        
        
        gosub do_cordic   'perform cos and atan functions to determine bearing and distance to waypoint    

         
   'adds angle of triange to quadrant angle. (Yeah, my quads don't match what you learned in school)
        if quadrant = 1 then b2dest = 900 - b2dest                  
        if quadrant = 2 then b2dest = 900 + b2dest                         
        if quadrant = 3 then b2dest = 2700 - b2dest             
        if quadrant = 4 then b2dest = 2700 + b2dest     
     
'    my quadrants
'            N          
'           |            
'       4   |   1
    'W______|________E    
'           |
'       3   |   2
'           |
'            S

The above code was for the cordic made for a Pic16f device. The PIC18 cordic allows positive and negative numbers, so it figures the quadrant for you.

See the cordic and the last post here:

http://www.picbasic.co.uk/forum/show...ghlight=cordic