Take the 2-minute tour ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

I suspect I'm trying to do the same thing as in Convert image in KMZ to polygon. Given a kml displaying an image within a given lat/long boundary, what are the steps I follow to use Quantum GIS to convert this KML to a vectorized polygon? The image is simply a solid color map -- I.E. the associated PNG simply has each pixel as a set color or as a transparency, and I'm intrerested in being able to query if an arbitrary lat/long is within the bounds of the vectorized polygon.

Edit: It doesnt look like I can open the kml directly. Its raster image is a PNG. How do I set the lat/long bounds of the image if I simply open this PNG as a raster layer?

share|improve this question
add comment

1 Answer 1

up vote 0 down vote accepted

It sounds like you need to first georeference your png file before converting it to a polygon.

http://qgis.spatialthoughts.com/2012/02/tutorial-georeferencing-topo-sheets.html

share|improve this answer
    
Yep, that's the keyword I needed. Georeference the image, enable the gdaltools plugin, Raster->Conversion->Polygonize, save the resulting vector in whatever format. Thanks. –  Oesor Feb 14 '12 at 17:39
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.