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I want to convert (google sourced) longitude and latitude coordinates to x and y to place points on a SVG map

I can get the longitude converted to X but I can't nail latitude.

http://jsfiddle.net/chrisloughnane/an3BZ/17/

  • red dots = place holders
  • green dot = calculated position from longitude/latitude

I have read so much about Mercator projections and other projection systems API's I am now completely confused. I also followed Proj4JS library threads but couldn't find an example that was close to my task.

I attempted to emulate this solution, unfortunately I got something wrong.

Could someone please have a look at my jsfiddle and see if it's an obvious mistake.

The second test function secondconvert(latitude, longitude) (bottom of javascript pane) provides me with a reasonably accurate x coordinate i.e. if I manually enter the y coordinate b.ylat change to 265 it covers my left red dot place holder nearly perfectly.

I think I'm close, any help would be really appreciated.

tia.

Original SVG from here.

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chris loughnane
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1 Answers1

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In your calculations of lattest and mapOffsetY inside secondconvert() you're using variable width where Raphael's solution uses worldMapWidth. Fixing that you get closer to the expected result, though still not precise.

acraig5075
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  • you **Sir are a star!** This was bothering me for a week. After correcting my error and then adjusting the southern latitude the results are accurate enough for the purposes of this project. Thank you very much for your help :P http://jsfiddle.net/chrisloughnane/an3BZ/40/ – chris loughnane Jul 05 '12 at 11:32