I'm quite a newbie in GIS.

I need to compute (without using any existing lib/tool) the longitude & latitude (WGS84) corresponding to the a pixel, inside a (georeferenced) map image.

I know:

  • the x,y coordinates or the pixel,
  • the width & height (pixels) of the map image,
  • the bounding box (lon/lat coordinates for the top-left, top-right, bottom-left & bottom-right vertices).

Intuitively I try to use longitude difference between top-left/top-right, in correlation with image width and pixel x to determine the corresponding longitude.

Please be open minded. I don't ask for a ready to use solution, but for documentation to understand the key concept required to do it.

  • What have you found/tried prior to posting? You seem to be simply stating an assigned problem. – PolyGeo Oct 21 '15 at 20:58
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    This reads like a homework assignment you were asked to complete... – DPSSpatial Oct 21 '15 at 21:02
  • If the image is projected then you're up the creek without a paddle... there is a good reason why we use libraries.You don't say what sort of image - accessing the georeference is different for most image formats and is only really easy with a world file (it's text) - which is a good reason to use a lib like GDAL which standardizes the obtaining of GeoTransform... it's not known if the image is rotated which would make it a bit more difficult. As a newbie in GIS I would strongly urge you to use an open source lib or the maths to achieve this would be too long to answer here. – Michael Stimson Oct 21 '15 at 22:18

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