Occassional thoughts about orienteering

Sunday, December 26, 2010

Some fieldchecking


The map clip shows a bit of terrain that I fieldchecked yesterday. The cliffs in this area are fairly low - mostly about 1.5 meters. I've used the boulder field symbol to show areas where the cliffs are either broken up or too low to be mapped as cliffs.

I've been using a laser scan (aka lidar) basemap with 2.5 meter contours and a "lutning" image from OL Laser. You can see a clip below. With a little bit of experience, the lutning image. With a little bit of experience comparing the lutning image to the terrain, you can really get a lot of information from it that makes fieldchecking a lot easier. The small black dots are usually the largest hardwood trees. The larger black blobs are typically cedar trees. The shading on the lutning image shows the steepness of the slop (darker is steeper). If you look at the area with the cliffs, you can see some of the shapes of the individual cliffs. It is actually a bit easier to see on the basemap than on the clip that I've posted below, but you should get the general idea.

When we first mapped the area - back in the late 1980s - our basemap had much less detail. Drawing the details in the rocky areas was extremely tedious and difficult to get right. You spent a lot of time using compass and pace and there weren't many strong fixed points on the basemap (though the contours were pretty good). As a consequence, we drew fewer details in the rocky areas.

I've become a big fan of OL Laser and, in particular, the lutning image (by the way, lutning is Swedish for slope, but I like the word lutning). The images are especially useful in the sort of terrain that is predominant around here. You can download OL Laser (it is free) and read about it at www.oapp.se. Click on the English flag for a Google translation and download a short set of instructions in English.

Back to okansas.blogspot.com.

posted by Michael | 10:03 AM


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