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QGIS 2.0 Working with tiff raster file. Reprojections are in WGS84 Mercator.

Here is my problem: I am trying to use buffers or urban areas to analyze light intensity on a raster layer. I want 30 miles, 60 miles, and 100 miles for the buffer sizes. I have reprojected the vector layers to WGS84 / World Mercator. When I ran a zonal statistics, everything went smoothly until I was double-checking the output. I saw "null" on a few of the rows of information in the data table. When I looked at the raster image, which I also reprojected to WGS84 / World Mercator, a large chunk of the raster layer was missing. Images below.

Non-reprojected raster layer: enter image description here

Reprojected raster layer: enter image description here

I am assuming there is a problem with my reprojections. I am still new at GIS, so please bear with me. Thanks in advance.

  • Welcome to GIS StackExchange. According to the screen shot, there is a raster layer in the second image that is not checked in the layer control. Is it the missing part? What tool did you use to reproject the raster? – Below the Radar Feb 20 '14 at 18:43
  • The unchecked layer is the original, non-reprojected tiff image. I put them in the same project to easily screenshot the difference. If I pull zonal statistics from the second image, I get the null inputs on parts of China and Japan. If I pull zonal statistics on the first image, I get null across the board. I reprojected by "save as..." – ian Feb 20 '14 at 18:53
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    see this post for raster reprojection info: gis.stackexchange.com/questions/38984/… , I suggest you to use GDALtool instead of save as – Below the Radar Feb 20 '14 at 18:55
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Looking at your image, I guess you are working on Asia, and the missing part is on the other side of 180°E/W. So you might find your data West of America.

You could reproject to another CRS based on some Asian meridian to avoid this.

By the way, World Mercator uses metres as units, but these are only true meters at the equator.

  • Thank you for the response. I am currently attempting Below the Radar's method. While I wait for the reprojection, I will tell you that I am looking at the entire globe. I have a vector layer of the 300 largest MSAs in the world. I will then draw a buffer in varying sizes around those points and analyze the light intensity within. Is there a better projection than World Mercator? – ian Feb 20 '14 at 19:35
  • world mercator is well known projection because used in many web maps like openstreetmap or google map, but maybe not the best for spatial analyses like you want to do, see this excellent website to choose the right projection for your need. – Below the Radar Feb 21 '14 at 0:47
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    The boundary goes through South Korea, just west of Japan, and well west of the 180 degree meridian. I'm having exactly the same problem, with different data but apparently cutting off at exactly the same place -- around 128 degrees east. – Max Jul 26 '14 at 21:42
  • @Max What CRS does the original raster layer have? – AndreJ Jul 27 '14 at 10:55
  • @AndreJoost: in my case the original had WGS84 and I'm outputting Mollweide; reprojecting the raster layer did the trick. – Max Jul 27 '14 at 12:52

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