#1 2016-12-03 12:22:46

asela115
Member
Registered: 2016-12-03
Posts: 1

import .shp files to WME

Hi,
I have Arcgis shape file having polygons with corresponding landuse IDs in its attribute table. When importing .shp file, MapEditor asks for internal and external roughness values.

It is possible to assign an internal roughness value for each polygon, but assigning external roughness value is difficult for a larger map. There are many cases where polygons are interfacing with multiple different other landuse types (which are having different roughness values). So external roughness value is also varying.Just assigning a internal roughness value only and importing to MapEditor gives so many crosspoint errors.

Is there a better approach when dealing with .shp files (rather than manually digitizing a larger map within MapEditor)

Thanks

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#2 2017-01-03 11:24:23

Ole Rathmann
Dr.
From: DTU-Wind, Risoe Campus
Registered: 2009-10-30
Posts: 29

Re: import .shp files to WME

Hi (whoever you are)  - I agree importing shape-files into the Map Editor for roughness lengths by polygons is problematic. I guess the bottleneck is really the cross-point errors, which is caused by overlapping line-segments of neighbouring polygons. The Map Editor is not sufficiently smart to see that these lines segments only touch but do not cross. How to work around? Well, do you have any possibility to change the polygons so that a a tiny space (a fraction of a meter) is left between them? Then it would be possible  - although tedious - to add the necessary external roughnesses ...
Another solution requires a bit of patience. We are just now finishng a new Map Editor version which is able to accept "unknown roughness" specification for e.g. external roughness of a polygon. The new Map Editor is - in the process just after reading - able to infer the missing roughness lengths from neighboring or surrounding roughness-change lines. But it would still require you to adjust the polygons to avoid overlapping. Another new feature is grid-file importing. So if you could convert the shape-file to a grid file (Surfer ASCII .grd format) the new map editor version would be able to read that right away - and convert it to a standard WAsP .map file.
/Ole Rathmann

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