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2012-03-18
GIS
9 Comments

Beautiful Global Projections – Adding Custom Projections to QGIS

This year we are celebrating Gerardus Mercator’s 500th birthday. We have all grown very accustomed to his Mercator projection but I want to take the chance to explore some alternatives:

Radical Cartography features an extensive projection reference compiled by Bill Rankin. One of the more exotic projections is “Van der Grinten I” by Alphons J. van der Grinten, 1898. It has a “pleasant balance of shape and scale distortion”. The “boundary is a circle” and “all parallels and meridians are circular arcs (spacing of parallels is arbitrary)”.

Using the name, we can try to find the projection definition on Spatialreference.org. One of the definitions that works well in QGIS is “ESRI:53029 Sphere Van der Grinten I” with the following proj4 string:

+proj=vandg +lon_0=0 +x_0=0 +y_0=0 +R_A +a=6371000 +b=6371000 +units=m +no_defs

In QGIS Settings – Custom CRS, we can add this projection to the list of available CRS:

  1. Press the “Star” button to add a new empty entry”
  2. Add the Name and proj4 string
  3. Press the “Save” button to make the changes permanent

Custom projection dialog

Once this is done, “Van der Grinten I” can be selected for on-the-fly reprojection. I’ve been using NaturalEarth’s land and ocean dataset. The result might not be a perfect circle (due to the coarseness of the dataset) but I find it very appealing:

Van der Grinten projection

9 comments

  1. I think the Antarctica is way too large, don’t you think?
    Generally I find the lack of some of projections the biggest problem of QGIS. That’s where ArcGIS definitely takes the lead. Why aren’t they included in QGIS by default?

    • pvanb said:

      I think QGIS is using proj4 for its projections? The proj4 program folder (usr/share/proj on my Ubuntu installation) contains an esri and an esri-extra files with additional projection which I assume are from esri (?) and which you can use in e.g., GRASS. Not sure if these are already included in QGIS, or if they are accessible from QGIS directly.

      • I’ve never seen Robinson, Winkel Tripel or Eckert etc. included in default QGIS installation. Adding them manually is the only way to use them.

      • underdark said:

        Could you share a working Winkel Tripel proj4 string? Spatialreference.org doesn’t seem to list it.

    • underdark said:

      I don’t know the process used to decide which CRS to include in QGIS projections database. It’s certainly a valid question to ask. CRS IDs of multiple authorities are listed but ESRI isn’t one of them.

  2. Kurt said:

    One of the most beautiful global projections is Robinson:
    +proj=robin +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs

    btw: do you know how to use winkel triple with qgis???

    thanks

    Kurt

    • underdark said:

      Sorry, no. But I’ll keep my eyes open.

  3. Nick Hopton said:

    I don’t think that Winkel Tripel is defined in Proj, or if it is I can’t find it. What one can do is to project WGS84 lat/lon vectors or rasters to Winkel Tripel in FlexProjector and then import them to QGIS for styling, labelling, &c.

    Here’s a link to a sad effort of my own:

    Natural Earth vectors with a FlexProjector graticule. One small problem with FlexProjector is that is doesn’t carry over the attributes from the original DBF to the new DBF, but these can be added later. Possibly just copying the original DBF and then renaming it would be enough. Being me, I did a cut and paste job in OO Calc.

    • Kurt said:

      Nick, you can find the winkel Tripel in the offiical docu:
      ftp://ftp.remotesensing.org/proj/OF90-284.pdf:
      +proj=wintri
      unfortunatly I was unable to enable it in qgis 1.74, while I was able to use the robinson