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8h
comment How to perform viewshed analysis with Dutch AHN files?
Compared to SRTM, the field values should indeed be heights in cm. It might help to recalculate them to meters using the field calculator. The results look different for me. In your example, the observer height is 1.6 (meters), while the raster data is about 6000 (cm). Apart from this plugin, GRASS and SAGA can also do viewshed analysis. github.com/zoran14/viewshed and hub.qgis.org/projects/viewshed/wiki give some hints on the usage.
19h
comment QGIS Wien 2.8. Openlayers plugin doesn't work
Is the plugin activated?
19h
comment How to perform viewshed analysis with Dutch AHN files?
BTW I used the qgis plugin, not GRASS.
19h
comment How to perform viewshed analysis with Dutch AHN files?
Yes, and actual instead of estimate even drags it further out.
1d
comment Getting NULL-values when point sampling USGS (SRTM 1 Arc-Second Global) grid (QGIS 2.8.2)
In QGIS, Raster -> Projection -> Reproject to another file name and the CRS of the point file. For vector layers, you can use Save As ... to the CRS of the raster.
1d
comment Getting NULL-values when point sampling USGS (SRTM 1 Arc-Second Global) grid (QGIS 2.8.2)
Are you sure that DEM and point layer are in the same CRS? I.e. turn OTF OFF and see if they still align.
1d
comment How to perform viewshed analysis with Dutch AHN files?
The plugin works for me with SRTM and with AHN data, but giving different results. Keep in mind that all layers should share the same CRS, and the AHN elevation should better be scaled from cm to meters. You should clip the AHN DEM to your area of interest to bypass memory error. If it does not work for you, add a screenshot with the plugin parameters you have set.
1d
answered How to perform viewshed analysis with Dutch AHN files?
1d
comment How to perform viewshed analysis with Dutch AHN files?
Which AHN set do you use? The AHN2 seems to have holes at buildings.
1d
answered How to place coordinates points on a vector layer?
1d
revised Using proj to convert EPSG:2263 to WGS84
added 65 characters in body
1d
answered Using proj to convert EPSG:2263 to WGS84
2d
comment Load USGS DRG into QGIS
+zone=17 identifies the central meridian, counting from -177°E eastwards in 6-degree-steps. +south is added for CRS below the equator.
2d
comment Load USGS DRG into QGIS
UTM projection normally does not use lat_2, lon_1 and lon_2 parameters.
2d
answered Load USGS DRG into QGIS
Jul
1
answered Where to download QGIS 2.10?
Jul
1
comment gdalwarp reprojection causes missing data
You might have to clip the source so that the poles are excluded before reprojection.
Jun
30
revised Put png map image as a background to draw upon
added 206 characters in body
Jun
30
comment Put png map image as a background to draw upon
The Georeferencer offers you an icon labelled From map canvas. All you have to do is search for the point on the base map, and click on it (and set the CRS in Settings -> Transformation Settings to EPSG:3857 as well).
Jun
30
comment Put png map image as a background to draw upon
It might help if you take the border points from the google map background to georeference. EPSG:3857 is correct for that. The city points might be the point of the fibre optic network switch, and not the town center.