![barsoom map barsoom map](http://www.tarzan.org/art/marsmap.jpg)
Then, you can just save it out as SVG (File>Export as SVG). I pointed them at the data I’d been playing with and set one to the N and one to the S projection, giving this: To do that, you make a print layout (Project>New Print Layout), and add two maps to it. OK, now I need the data in SVG format so I can load it into Inkscape. I added a filter (Layer->Filter) of "SphLen_km" > 400 to exclude any features less than 400Km in length: this cut out loads of noise in my map. One of these attributes is “SphLen_km”, which I read as the spherical length in kilometres” (Spherical length being along the outside sphere, rather than the direct length between two points). You can open up the numerical data attached to the features “Layer>Open Attribute Table”: you’ll see the set of data associated with each feature in a table. In GIS speak anything plotted on a map is known as a “Feature”. I tweaked the data a wee bit to reduce the number of details shown: the underlying data is a set of lines giving the geological boundaries on Mars. Now, I can just change the projection and the display updates correctly! (This is the north pole of Mars) However, I found QGis still had problems: the solution was to add the +R=3396190 expression:
Barsoom map how to#
We can now transform it.īack to the original blog post, the author mentions how to do Orthographic North and South Polar projections. This doesn’t make any visible change, but it tells QGis the details of the data its showing. So I defined that as a custom projection in QGis (Settings->Custom Projection) and applied it to the data (bottom right icon, probably reading “Unknown CRS”). The key is of course the +R=3396190, the radius of Mars in metres (when treated as as a simple Spheroid). More searching… I eventually figured out that this “proj” format projection described the data in the file: QGis doesn’t know about the “Robinson_clon0_Mars_2000_Sphere” projection, so – apart – from displaying the data as in the file, its not able to do projection transformations. These stem from the fact that most GIS work is done on Earth data, and this is an entirely different planet. Its complaining about “No transform available between EPSG:4326 and Robinson_clon0_Mars_2000_Sphere” at the top in red.I want a circular Orthographic projection, not the squished “Robinson” one.Use the QGIS Browser to find the SIM3292_geodatabase.gdb folder, then double click the files to open them: Loading it up yielded what the blog post said, the mars data in an Eckert IV projection. Hmm, well, I’ve used QGis before for work (and also for fun ? ), though not for a couple of years. But, importantly, the author had a copy of the Mars geological survey data in GeoDatabase format. The result of that project is lovely, but its not quite what I’m doing. Where to get the map though? Well, while browsing around, I found this blog post. I always liked the name for Mars, “Barsoom” from Edgar Rice Burroughs’ Mars Series, so that would be the title. I’d bought some red card from Hobbycraft, so Mars was the obvious choice. The circular cutout of my previous project gave me an idea: what if I drew a planet next?