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I am a journalist.

My goal: A globe that shows the range ok North Koreas ICBMs - the azimuthal equidistant projection centered on NK.

My steps so far:

  1. Created Standard QGIS project (EPSG:4326)
  2. Imported a world shapefile (EPSG:4326). The center of the shapefile is in Greenwhich.
  3. Imported a CSV with the lat/long of Pyongyang
  4. Used MMQGIS to create a buffer (13,000 km)

  5. Created a Custom CRS with these details:

    +proj=ortho +lat_0=39.03385 +lon_0=125.755504 +x_0=0 +y_0=0 +a=6371000
    +b=6371000 +units=m +no_defs

Didn't look so nice (and since the US was not visible it was useless for me)

  1. Created a different Custom CRS with these details:

    +proj=aeqd +lat_0=39.03385 +lon_0=125.755504 +x_0=0 +y_0=0 +a=6371000 +b=6371000 +units=m +no_defs +proj=aeqd +R=6371000 +lat_0=39 +lon_0=125

My problem:

enter image description here

Being not a GIS pro, I would be quite proud of myself - if there wasn't a part of the buffer (=range) missing - exactly at the line where my original shapefile "ended."

For the record, I checked posts like: - Map Range of Airplanes - Manipulating Azimuthal Equidistant Projections in QGIS - How do I project a Azimuthal Equidistant global map into a circle in QGIS?

I also tried to first create a new shapefile centered on the pacific using QGIS display world country shape files centered on pacific ocean using Robinson, Miller Cylindrical or other projection but that also did not work.

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    Looks like you're getting chopped off at the 180 degree meridian. Can you reproject your lat/long point to your Custom CRS before buffering? (In fact, it's not clear to me how you can specify a buffer distance in km if your data-to-be-buffered are in lat/lon degrees.)
    – Jon
    Commented Oct 29, 2018 at 21:27
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    Indeed, you need to create the buffer after specifying your custom project crs. Also, there is no need to repeat parameters in the crs, just +proj=aeqd +lat_0=39.03385 +lon_0=125.755504 +x_0=0 +y_0=0 +a=6371000 +b=6371000 +units=m +no_defs should work fine
    – FSimardGIS
    Commented Oct 29, 2018 at 21:32
  • Your post reminds me of this article about a buffer error around North Korea in a magazine once
    – FSimardGIS
    Commented Oct 29, 2018 at 21:38

1 Answer 1

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The problem is that you have created your buffer while your project crs was still in EPSG:4326. Doing so will create an erroneous buffer, plus you are going to have map unit problems as well, since geographic coordinates are angles, not linear units. To resolve the problem, you will have to create your buffer while your project crs is set to azimuthal equidistant.

So here are the steps in the correct order:

  • Create QGIS project (EPSG:4326)

  • Import a CSV with the lat/long of Pyongyang

  • Set the project crs to your custom crs +proj=aeqd +lat_0=39.03385 +lon_0=125.755504 +x_0=0 +y_0=0 +a=6371000 +b=6371000 +units=m +no_defs

  • Then create the 13,000,000 meter buffer

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