The orienteering maps on these pages are made purely based on LIDAR-data and aerial imagery, with no field work, but with a good amount of real intelligence. The production method is developed over a few years and includes, despite the availability of automated cartography, mostly manual work. Despite this, depending on the type of terrain, I may come up with a decent map using about 6-8 hours per km2.

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In some types of terrain, the map is almost as good as a surveyed one, or there’s an old map of the area. In other types, the map is an excellent base map for the field work.

 

The base material

To start with, I download LIDAR data from hoydedata.no. I download both the DTM – the terrain model, and the DOM – the surface model. These come as a set of TIF-tiles.

• I combine and resample these using gdalwarp. I have landed on 0.5m resolution, which gives me a fairly good view of streams, ditches, crags and even narrow paths.

• I also download the LAS-files for the automatic map generation. I only use the vegetation output.

• I then generate a hill shade from both the merged DTM and DOM.

• I generate a forest height model by subtracting the DTM from the DOM, i call it diff.

• I generate contours with 1m equidistance from the DTM. I later add an “index” field, having the following values:

  • 2 if the elevation is dividable by 25 (elev % 25 = 0)

  • 1 if the elevation is dividable by 5 (elev % 5 = 0)

  • 0 otherwise

• And finally, I generate a slope shade, the same way as the shade from the DTM, but with the sun placed in zenith. I usually modify this in Photoshop so I’m left with only the steepest part of the terrain not being white, that’s going to help me with crags and cliffs.

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I use Karttapullautin to generate the greenery. I run it the usual way, but only use the vegetation file that you find in the temp directory after the analysis.

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I then combine these files in QGIS to produce two background images (added on top of each other using multiply blending mode):

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• The GND, which consist of

  • Situation from a WMS-server.

  • slope shade

  • contours

  • DTM hillshade

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• The VEG, which consist of

  • the hillshading from the DOM.

  • the vegetation from Karttapullautin (but with the yellow band turned off)

  • vegetation height. I use a white to dark red colour scale, but leaving everything under 1m yellow.

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Finally, I need aerial imagery, or orthophoto. These are generally not free in Norway. Clubs may get access to these for orienteering maps, but most often I find it easier to just take screen dumps from norgeibilder.no and stitch them together in Photoshop. The nice thing about norgeibilder.no is that it allows you to select amongst several vintages of images. Some sets are photographed with a more favorable sun direction, or early enough in the spring that there are no leaves on the trees. Sometimes, old images with an old felled area may reveal the location of boulders and other objects.