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I am working with the Natural Earth world map as a SHP file, but when I try to change the prime meridian (PRIMEM) of the coordinate system

GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]

I get this:

enter image description here

Projections seem to give the same results. What is happening here?

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  • Do you need polygons? - if lines then reproject your data to the meridian you want.
    – Mapperz ♦
    Commented Apr 27, 2012 at 19:51
  • just noticed the mapguide tag. is this shapefile or sdf, oracle?
    – Brad Nesom
    Commented Apr 27, 2012 at 19:56
  • Shapefile, loaded into MapGuide
    – Garrett Hall
    Commented Apr 27, 2012 at 20:28

2 Answers 2

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you might try exporting the data or possibly run it through a fix geometry (I use et geotools).
It looks to me lie with the new meridian you are splitting some polygons and that is causing the fill to "leak" out.

arcmap1

arcmap2

et tools

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3
  • What does a fix geometry involve? Export it to what format?
    – Garrett Hall
    Commented Apr 27, 2012 at 18:53
  • fix geomtery is in et tools. it outputs a shape file. geometry repair is avail at the editor level arcmap and performs it on the existing feature class.
    – Brad Nesom
    Commented Apr 27, 2012 at 19:50
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    You were right, the shapes are getting "stretched" across the map which was causing the distortion. The shapes need to be "cut" before changing the meridian.
    – Garrett Hall
    Commented Apr 30, 2012 at 17:28
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natural earth is cropped at 180°, so all is ok, if your prime-meridian is 0°. when you change the prime-meridian e.g. to 90°east some country-boundaries go beyond the right or left map-border and "continue" on the other side of the map.

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3
  • Is there any way to change the meridian and not cause this?
    – Garrett Hall
    Commented Apr 27, 2012 at 18:53
  • as far as I know there is no easy way, you have to do this manually, which is a real pain. but perhaps anyone knows an easy way??
    – Kurt
    Commented Apr 30, 2012 at 17:47
  • I am working on a data translation script to do this (cut the shapes and rotate meridian). Unfortunately we use proprietary tools (FME) so I cannot post a general solution.
    – Garrett Hall
    Commented Apr 30, 2012 at 19:27

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