Re: [OSM-dev] Plotting data on an equirectangular map, distorted for sphere projection
Alright,
Thanks to some great feedback, I've made some good progress on getting
distortions to look better on a sphere. It's not perfect yet, but getting
close. Perhaps I just need to do a little more research on different
projections and more trial and error.
Here's what I've done so far:
#Create mml file with Mollwide projection specifed in Map:
?xml version=1.0 encoding=utf-8?
Map srs=+proj=moll +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84
+units=m +no_defs
Stylesheet![CDATA[
*
{
map-bgcolor: #69f;
}
#world-borders
{
/*line-width: 1;
line-color: #696;*/
polygon-fill: #6f9;
}
#world-borders NAME
{
text-face-name: DejaVu Sans Book;
text-size: 24;
text-fill: #000;
text-halo-fill: #9ff;
text-halo-radius: 2;
text-placement: point;
text-wrap-width: 50;
text-avoid-edges: true;
}
#world-outline
{
line-width: 10;
line-color: #696;
}
]]/Stylesheet
Layer id=world-outline srs=+proj=merc +a=6378137 +b=6378137
+lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null
+wktext +no_defs +over
Datasource
Parameter name=typeshape/Parameter
Parameter name=filesample_data/world_merc.shp/Parameter
/Datasource
/Layer
Layer id=world-borders srs=+proj=merc +a=6378137 +b=6378137
+lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null
+wktext +no_defs +over
Datasource
Parameter name=typeshape/Parameter
Parameter name=filesample_data/world_merc.shp/Parameter
/Datasource
/Layer
/Map
#create XML
cascadenik-compile.py shapeTest.mml shapeTest.xml
#create Mollwide projection:
nik2img.py shapeTest.xml shapeTest.tif -d 4096 2048 --bbox -180.0 -90.0
180.0 90.0
http://www.flickr.com/photos/8139783@N08/9319568407/
#reproject as EPSG:4326
gdalwarp -s_srs '+proj=moll +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84
+datum=WGS84 +units=m +no_defs' -t_srs EPSG:4326 -te -180.0 -90.0 180.0
90.0 -ts 4096 2048 -overwrite shapeTest.tif shapeTestOut.tif
http://www.flickr.com/photos/8139783@N08/9319567933/in/photostream/
#3D render previews:
http://www.flickr.com/photos/8139783@N08/9322359900/in/photostream/
http://www.flickr.com/photos/8139783@N08/9322359828/in/photostream/ (lines
and text a touch thicker near the poles, labels a touch skewed? - so close!)
*Update as I write:*
I can guess that the text is getting skewed due to the stretching from one
projection to the other (more stretching towards the right and left edges).
I imagine that I'll need to calculate and place text separately. Science On
a Sphere allows text to be placed via an accompanying dataset text file as
well. Also, if I make the map outlines, inlines, things seem to stay less
stretched near the poles.
http://www.flickr.com/photos/8139783@N08/9323320848/ (lines may appear
deceiving as I thinned them out a bit compared to above links)
Thanks again for the feedback. Any additional ideas are welcome as I
research more.
Best regards,
Chris
On Thu, Jul 18, 2013 at 2:12 AM, Martin Raifer tyr@gmail.com wrote:
Hi!
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...
Cheers,
Martin
___
dev mailing list
dev@openstreetmap.org
http://lists.openstreetmap.org/listinfo/dev
Re: [OSM-dev] Plotting data on an equirectangular map, distorted for sphere projection
Hi! 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... Cheers, Martin Christopher Stevens ch...@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, but should work for illustration purposes: http://www.flickr.com/photos/8139783@N08/9309514743/ Now to add some basic large labels: http://www.flickr.com/photos/8139783@N08/9309518499/in/photostream/ If I then project this on a sphere (virtual one in this example, but looks the same in real projection), the geography placement looks great and lines 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/ - side view http://www.flickr.com/photos/8139783@N08/9309514685/in/photostream/ - pole view, the presenter often turns the globe this way for audience Let me know if that helps illustrate the challenge better. Thanks again, Chris On Wed, Jul 17, 2013 at 11:41 AM, Dane Springmeyer d...@dbsgeo.com wrote: Chris, It would be helpful to explain what you've tried already. Mapnik supports 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 this 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 http://spatialreference.org/ref/epsg/3786/ The specific Mapnik Map XML syntax can be found by following the link for Mapnik XML like: http://spatialreference.org/ref/epsg/3786/mapnik/ Dane On Jul 17, 2013, at 9:41 AM, Christopher Stevens ch...@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 good 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 examples cover this as well). The challenge is that I'm then projecting this on Science On a Spherehttp://www.spacefoundation.org/visit/northrop-grumman-science-center-featuring-science-sphere/science-sphere%C2%AE, which requires equirectangular images that distort more towards the poles. Here's a quick example of something I made in a 3D program to show latitude and longitude lines (note how the lines and labels get fuzzy and stretched near the poles). http://www.flickr.com/photos/8139783@N08/9305646391/ Is there a way to add this type of distortion in mapnik? I'm guessing not 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 questions. Best regards, Chris ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
[OSM-dev] Plotting data on an equirectangular map, distorted for sphere projection
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 good 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 examples cover this as well). The challenge is that I'm then projecting this on Science On a Spherehttp://www.spacefoundation.org/visit/northrop-grumman-science-center-featuring-science-sphere/science-sphere%C2%AE, which requires equirectangular images that distort more towards the poles. Here's a quick example of something I made in a 3D program to show latitude and longitude lines (note how the lines and labels get fuzzy and stretched near the poles). http://www.flickr.com/photos/8139783@N08/9305646391/ Is there a way to add this type of distortion in mapnik? I'm guessing not 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 questions. Best regards, Chris ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
Re: [OSM-dev] Plotting data on an equirectangular map, distorted for sphere projection
Hi Am 17.07.2013 15:41, schrieb Christopher Stevens: 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 good to start here first. Mapnik is capable of rendering data in nearly any possible projection - and it can be done with osm-data, too. On http://polar.openstreetmap.de/ we do a rendering in EPSG:3031 Antarctic Polar Stereographic projection. Code and documentaztion can be found here: https://github.com/MaZderMind/mapnik-stylesheets-polar However those projections are applied to the geometries *before* rendering out a planar, rectangular image. 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 examples cover this as well). The challenge is that I'm then projecting this on Science On a Sphere http://www.spacefoundation.org/visit/northrop-grumman-science-center-featuring-science-sphere/science-sphere%C2%AE, which requires equirectangular images that distort more towards the poles. Here's a quick example of something I made in a 3D program to show latitude and longitude lines (note how the lines and labels get fuzzy and stretched near the poles). http://www.flickr.com/photos/8139783@N08/9305646391/ This however looks like an post-render distortion, so I'd guess you'd have to apply some filter to the rendered mapnik images. Is there a way to add this type of distortion in mapnik? I'm guessing not 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. I'd bet that it would be better to use sth. like graphicsmagick or a custom program with libpng to do the pixel-transformations after the rendering finished. Peter ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
Re: [OSM-dev] Plotting data on an equirectangular map, distorted for sphere projection
Peter, Thanks for the helpful info! It's much appreciated (and I just realized I posted to OSM list instead of mapnik, helpful anyway!). I'll look deeper into post-render distortion. Kind regards, Chris On Wed, Jul 17, 2013 at 8:40 AM, Peter Körner osm-li...@mazdermind.dewrote: Hi Am 17.07.2013 15:41, schrieb Christopher Stevens: 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 good to start here first. Mapnik is capable of rendering data in nearly any possible projection - and it can be done with osm-data, too. On http://polar.openstreetmap.de/ we do a rendering in EPSG:3031 Antarctic Polar Stereographic projection. Code and documentaztion can be found here: https://github.com/MaZderMind/mapnik-stylesheets-polar However those projections are applied to the geometries *before* rendering out a planar, rectangular image. 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 examples cover this as well). The challenge is that I'm then projecting this on Science On a Sphere http://www.spacefoundation.org/visit/northrop-grumman-science-center-featuring-science-sphere/science-sphere%C2%AE , which requires equirectangular images that distort more towards the poles. Here's a quick example of something I made in a 3D program to show latitude and longitude lines (note how the lines and labels get fuzzy and stretched near the poles). http://www.flickr.com/photos/8139783@N08/9305646391/ This however looks like an post-render distortion, so I'd guess you'd have to apply some filter to the rendered mapnik images. Is there a way to add this type of distortion in mapnik? I'm guessing not 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. I'd bet that it would be better to use sth. like graphicsmagick or a custom program with libpng to do the pixel-transformations after the rendering finished. Peter ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev -- Christopher Stevens 303.929.7863 cell www.christopherstevens.cc ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
Re: [OSM-dev] Plotting data on an equirectangular map, distorted for sphere projection
Chris, It would be helpful to explain what you've tried already. Mapnik supports 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 this 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 http://spatialreference.org/ref/epsg/3786/ The specific Mapnik Map XML syntax can be found by following the link for Mapnik XML like: http://spatialreference.org/ref/epsg/3786/mapnik/ Dane On Jul 17, 2013, at 9:41 AM, Christopher Stevens ch...@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 good 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 examples cover this as well). The challenge is that I'm then projecting this on Science On a Sphere, which requires equirectangular images that distort more towards the poles. Here's a quick example of something I made in a 3D program to show latitude and longitude lines (note how the lines and labels get fuzzy and stretched near the poles). http://www.flickr.com/photos/8139783@N08/9305646391/ Is there a way to add this type of distortion in mapnik? I'm guessing not 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 questions. Best regards, Chris ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
Re: [OSM-dev] Plotting data on an equirectangular map, distorted for sphere projection
On Thu, Jul 18, 2013 at 1:41 AM, Dane Springmeyer d...@dbsgeo.com wrote: Chris, It would be helpful to explain what you've tried already. Mapnik supports 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 this 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 http://spatialreference.org/ref/epsg/3786/ The specific Mapnik Map XML syntax can be found by following the link for Mapnik XML like: http://spatialreference.org/ref/epsg/3786/mapnik/ I don't think Chris' problem is setting the appropriate projection in Mapnik. What he needs is a way to distort the elements on the map (like text) such that if the map is used as a bitmap texture for a spherical 3D model, the map elements don't look distorted. ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
Re: [OSM-dev] Plotting data on an equirectangular map, distorted for sphere projection
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, but should work for illustration purposes: http://www.flickr.com/photos/8139783@N08/9309514743/ Now to add some basic large labels: http://www.flickr.com/photos/8139783@N08/9309518499/in/photostream/ If I then project this on a sphere (virtual one in this example, but looks the same in real projection), the geography placement looks great and lines 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/ - side view http://www.flickr.com/photos/8139783@N08/9309514685/in/photostream/ - pole view, the presenter often turns the globe this way for audience Let me know if that helps illustrate the challenge better. Thanks again, Chris On Wed, Jul 17, 2013 at 11:41 AM, Dane Springmeyer d...@dbsgeo.com wrote: Chris, It would be helpful to explain what you've tried already. Mapnik supports 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 this 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 http://spatialreference.org/ref/epsg/3786/ The specific Mapnik Map XML syntax can be found by following the link for Mapnik XML like: http://spatialreference.org/ref/epsg/3786/mapnik/ Dane On Jul 17, 2013, at 9:41 AM, Christopher Stevens ch...@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 good 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 examples cover this as well). The challenge is that I'm then projecting this on Science On a Spherehttp://www.spacefoundation.org/visit/northrop-grumman-science-center-featuring-science-sphere/science-sphere%C2%AE, which requires equirectangular images that distort more towards the poles. Here's a quick example of something I made in a 3D program to show latitude and longitude lines (note how the lines and labels get fuzzy and stretched near the poles). http://www.flickr.com/photos/8139783@N08/9305646391/ Is there a way to add this type of distortion in mapnik? I'm guessing not 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 questions. Best regards, Chris ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev -- Christopher Stevens 303.929.7863 cell www.christopherstevens.cc ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
