This is particularly important for creating points, which in Inkscape must be approximated by drawing a shape (such as a triangle) around the desired point location. dxf files we need to export to are lines ONLY. In the example below, I pasted in the base image, drew a triangle, and then copied it to create a set of points. However, they need to be in separate drawings to export separately. Inkscape also has a (rudimentary) layer system, if you want to keep geometry on different layers, which can make selecting them easier (for example points on one layer and borders on another). There's not much to drawing, use the pen tool (tooltip: "Draw Bezier curves and straight lines"), and you may want to turn on the grid in View -> Grid (you can also modify the grid in File -> Document Properties. Obviously this is arbitrary compared to a proper geographic coordinate system, but it means that the image and the geometry overlap perfectly when plotted in R. > Page, and should look like this:Īll this meant that coordinates of all the geometry will be based on the pixel position on the image. These options are acccessible through File -> Document Properties.
This was imported into Inkscape, with the dimensions of the Inkscape canvas matched to the resolution of the image (Note: the canvas units were changed to pixels). We used a satellite image (literally a screen grab) as the starting point. I'm not going into major detail on how to use Inkscape, but there are some important points of this workflow: Non-geographic Coordinates dxf format lines, which can be converted to spatial objects in R and treated as GIS data for all intents and purposes. Inkscape is a free, open source vector drawing program. Ultimately, the maps are output as images the same resolution as the original reference satellite image, and used as swappable textures within a Unit圓D virtual environment. In general, Inkscape is used to create vector data (points and polygons), which are then treated as GIS data in R to make a series of simple thematic maps. Why? Our use case was simply creating a set of example maps quickly while not having access to "real" GIS software such as ArcGIS or QGIS. This is a quick and dirty rundown of how to create "fake" GIS data using open source tools (a combination of Inkscape and R). Creating Artificial GIS Data with Open Source Tools
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