Converting Longitude & Latitude to X Y on a map with Calibration points

Question

If i have a jpeg map with size sizeX, sizeY

and some calibration points on the map (X, Y, Lon, Lat)

What would be the algorithm for calculating the corresponding XY point in the map with a given Longitude / Latitude pair?

Answer 1

Here's what worked for me, without so much bs.

int x =  (int) ((MAP_WIDTH/360.0) * (180 + lon)); int y =  (int) ((MAP_HEIGHT/180.0) * (90 - lat)); 

The lat,lon coordinates were given to me by Android devices. So they should be in the same standard used by all Google Earth/Map products.

Answer 2

If using the Equidistant Cylindrical Projection type map, here is what you need to do:

1. Find the Latitude and longitude of your location tutorial here:
   http://lifehacker.com/267361/how-to-find-latitude-and-longitude
2. Input that information into the following formulas:
   x = (total width of image in px) * (180 + latitude) / 360
   y = (total height of image in px) * (90 - longitude) / 180
   
   note: when using negative longitude of latitude make sure to add or subtract the negative number i.e. +(-92) or -(-35) which would actually be -92 and +35
   
   
3. You now have your X and Y to plot on your image
   
   More information can be found about this formula and the map type here:
   http://www.progonos.com/furuti/MapProj/Dither/CartHow/HowER_W12/howER_W12.html#DeductionEquirectangular