Tagged Questions
1
vote
1answer
23 views
Why does the Zonal Statistics tool always return 0?
I have a slope raster created from a DEM raster with the DEM Analysis tool.
Now, I would like to calculate the average slope in a given area represented by a vector polygon layer.
I thought I could ...
1
vote
0answers
18 views
QGis Grid statistics for polygons error - Module caused access violation!
I'm trying to calculate statistics for a raster layer using an overlaying polygon layer, I'm using SAGA "Grid Statistics for polygons" function, but it returns an error, sadly.. So in the sextante log ...
1
vote
1answer
44 views
Grass7 - r.regression.multi and new raster
I am on the learning curve with Grass7. I managed to make r.regression.multi work, but there is one thing that would be of high interest for me: it is possible to create a new raster showing the ...
1
vote
1answer
76 views
raster statistics - regressions between raster data
I have the following problem:
I have two set of rasters, with data that should correlate...one are measured data, one are modelled data. The correlation is weak, however, when looked at with a normal ...
4
votes
2answers
110 views
GDAL does not ignore NoData value
I am trying to calcualate the statistics of a TIFF. The script should ignore the NoData value, but doesn't. What causes this?
import gdal
from gdalconst import *
# register all of the drivers
...
3
votes
2answers
169 views
How to create a standard deviation map from three rasters in QGIS?
I have 3 normalised (0-100) raster maps. Is it possible to get a map which shows the standard deviation? I'd like to see the areas with smaller and higher std deviation.
Thank you!
6
votes
3answers
505 views
How to sum up pixel values in QGIS?
I need to know the value of the sum of all pixels in a raster. However, in the Statistics section of the Metadata tab in Properties, under Sum of All Cells it always indicates 0.00. I have tried with ...
9
votes
5answers
2k views
Get Raster Values from a Polygon Overlay in Opensource GIS Solutions
I have two layers. A polygon-shape-layer with many tiles and a raster-layer containing CORINE 2006 land cover with many categories in a colourmap.
I want to obtain for each polygon in the shapelayer a ...
6
votes
3answers
2k views
How to calculate raster statistics for polygons?
how can I calculate sums, averages etc of raster-points (multi-band) per polygon of a vector-layer. I was told that this is called "zonal statistics". I tried that with QGIS first.
There is a way to ...
