Mapping across boundaries

I’ve been involved in several mapping projects where I either had to work with data from both sides of a national boundary, or with data crossing the 180/-180 line, and the problems that brings with it.

The first one, using data in 2 different data models, 2 different projections and 2 different dates of capture obviously is a tricky one. This particular project, merging Dutch and Belgian topographic data, brought some interesting results and insights in how the 2 different NMA’s (the Topografische Dienst Kadaster in The Netherlands and the Nationaal Geografisch Instituut in Belgium) create and supply data. Hopefully we can show some results of this soon.

The other one, mapping several of the island nations in the Pacific that either cross or are very close to the 180/-180 line, such as Kiribati, brought a lot of logistical problems in GIS. When looking at a ‘classic’ map of the world, centered on Greenwich, these countries appear on either side. But since GIS software, or more specifically the LL84 projection in GIS software, also consider the world in this fashion, datasets end up in separate pieces. Bringing them together in this case involves manually adding one of the parts. It kind of makes you happy there isn’t a whole lot to map in Kiribati anyway…

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