[OSM-dev] Plotting data on an equirectangular map, distorted for sphere projection
tyr.asd at gmail.com
Thu Jul 18 08:12:21 UTC 2013
Just a wild guess (didn't try), but what if you rendered your map in an
equal area projection (e.g. Mollweide) and reprojected the resulting
raster image - in a second step - to equirectangular (for example using
GDAL)? That could result in something more towards your objective...
Christopher Stevens <chris at christopherstevens.cc>:
> Hello Dane,
> Thanks for taking a look. So far I can produce an EPSG:4326 image nicely,
> your comment boosted that setup (thanks!). This one is quick and ugly,
> should work for illustration purposes:
> Now to add some basic large labels:
> If I then project this on a sphere (virtual one in this example, but
> the same in real projection), the geography placement looks great and
> up well with other datasets. The styling gets odd with labels and lines
> getting thinner horizontally.
> http://www.flickr.com/photos/8139783@N08/9309514621/in/photostream/ -
> http://www.flickr.com/photos/8139783@N08/9309514685/in/photostream/ -
> view, the presenter often turns the globe this way for audience
> Let me know if that helps illustrate the challenge better.
> Thanks again,
> On Wed, Jul 17, 2013 at 11:41 AM, Dane Springmeyer <dane at dbsgeo.com>
>> It would be helpful to explain what you've tried already. Mapnik
>> proj4 and proj4 understands quite a few projections. I'm no expert in
>> equirectangular projections but
>> https://en.wikipedia.org/wiki/Equirectangular_projection states that
>> is basically a term for the well know set of lon/lat based geographic
>> coordinate systems.
>> So, can you try simply changing your Mapnik Map `srs` value to EPSG:4326
>> or a specific Equidistant cylindrical projection like
>> The specific Mapnik Map XML syntax can be found by following the link
>> "Mapnik XML" like:
>> On Jul 17, 2013, at 9:41 AM, Christopher Stevens <
>> chris at christopherstevens.cc> wrote:
>> Hello gurus,
>> I'm thinking that I may need to find some alternative data visualization
>> software to make this work, but I love mapnik and thought it would be
>> to start here first.
>> I'm hoping to create a basic themed map of different types of data and
>> plot it on a full-Earth image (I can figure this part out, starter
>> cover this as well). The challenge is that I'm then projecting this on
>> On a
>> which requires equirectangular images that distort more towards the
>> Here's a quick example of something I made in a 3D program to show
>> and longitude lines (note how the lines and labels get fuzzy and
>> near the poles).
>> Is there a way to add this type of distortion in mapnik? I'm guessing
>> as mapnik is optimized for other uses (but who knows). I'm guessing
>> that it
>> would "work" as is, but labels would get distorted (there are
>> work-arounds), and lines would get very thin near the poles.
>> Thanks for the feedback in advance. Let me know if I can answer any
>> Best regards,
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