Hi! I was using Arc/Info under Windows XP and now I migrated to Linux Gentoo and want to migrate to QGIS.
One of the tasks I used Arc/Info for is *height (elevation) matrix creation*. I have polyline and point layers as sources. The former layer is more accurate. In Arc/Info I did it in two steps: 1) TIN creation from polyline layer. I also use a territory polygonal layer to limit interpolation borders (so called '*soft clip*'). 2) Convert TIN to Raster (in Arc/Info Binary Grid, *.adf) with 100*100 meters cell size. As a result I had 547 Mb raster layer *.adf file and some smaller informative *.adf files. I read QGIS 1.3.0 user guide and Marco's "Terrain Modelling with Triangle Based Free-Form Surfaces" thesis and as I understand there is only possibility to use point layers to create TIN in QGIS?! So, I tried this functionality in QGIS 1.4.0 under Gentoo Linux. I projected my point layer from Geographical Coordinate System to Projected CS (WGS84). Then set it as the source in Interpolation Plugin window and chose 100*100 (as I understand in meters) cell size of output layer. I don't know which format QGIS saves TIN in and there is no filters of file extensions in "Save interpolated layer as..." window. So, I simply chose "tin.adf". As a result of interpolation I have 2,5 Gb file, that seems to be less accurately than my 547 Mb Arc/Info Binary grid one. Some questions: 1) Is there a possibility in QGIS to use *polyline *layer as a source of interpolation (TIN creation)? If no, is it possible to add this functionality in the future? 2) Is there a possibility in QGIS to *limit* interpolation borders by another polygonal non-heights layer (such as Arc/Info 'soft clip')? 3) What is a dimension of cell coordinates? Are they use the same units as projected point layer units? 4) Which format QGIS saves TIN in?
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