0
votes
0answers
25 views

Help with scripts for processing raster files with the raster calculator in QGIS

I am trying to process some raster files using python scripts in Qgis 2.20, and I have been having trouble finding any documentation on using raster calculator in scripts being run in the processing ...
3
votes
1answer
37 views

Expand raster extent and set expanded values using nearest neighbor sampling

I have run a hydrodynamic model which has given me a grid of surface elevations throughout a bay. I am trying to process the results in ArcMap (or QGIS if needed). My goal is to take the current grid ...
0
votes
0answers
13 views

map composer grid annotation in DMS format [duplicate]

I have digitized a map using CRS EPSG:4326 in QGIS. In Map Composer I set the grid. I can't get the annotation to display as DMS (degrees-minutes-seconds) rather than DD (decimal degrees) format. What ...
0
votes
1answer
35 views

How to isolate certain raster values using raster calculator?

I have a one band grayscale image. It has values 0-63 within the band. I need to isolate some of those values. Is there a way to do this in the raster calculator? QGIS 2.2//Windows 7
0
votes
0answers
28 views

Extract raster values under under each polygon buffer in qgis

In qGIS: I have raster file and >100 points. I constructed buffers polygons (vector-->geoprocessing-->buffer) around each of the points. Than I clipped (raster-->extraction-->clipper) the raster file ...
0
votes
1answer
43 views

Problems running model in QGIS

I am trying to make a batch model to convert band 2 and band 1 MODIS 8 day composites into NDVI. The input files are in tif format, but I want the output to be saved in Idrisi .rst format. I am ...
0
votes
0answers
16 views

Cell Statistics in QGIS

Cell Statistics in ArcGIS will calculate the mean (or statistic of choice) among multiple rasters on a cell-by-call basis. Can QGIS do this? If so, how?
2
votes
1answer
42 views

Calculating Topographic Exposure with Raster Calculator

I need you help trying to calculate Topographic Exposure (TOPEX) on a DEM in ArcGIS. I am trying to figure out wind exposure on a DEM with 25m cells. There is a great blog post where someone explains ...
1
vote
1answer
53 views

Floating point calculations in QGIS

How do I manage floating point calculations in QGIS? I have carried out 3 consecutive calculations on landsat bands. I end up with 32 bit floating point rasters on which I can't carry out a 4th ...
3
votes
1answer
60 views

Where is qgis getting the NO DATA value from?

I have a project that contains an 8-bit paletted layer (call it the mask layer) and a float 32 single band layer (call this the clip layer). I create a new raster by using the raster calculator, ...
0
votes
1answer
34 views

QGIS Raster Calculator dialog doesn't resemble that in documentation

I'm very new to QGIS. Raster Calculator looks (from online sources) like it ought to have all kinds of buttons and fields. Mine is rather stripped down. I have two rasters open, and I just want to ...
1
vote
1answer
71 views

How to change raster cell values within a polygon using QGIS GUI?

I would like to know how to change the values of raster cells which are within a polygon, leaving all cell values outside the polygon unchanged. I would like to subtract 1.5m from each raster cell ...
3
votes
0answers
61 views

Creating a new raster based on pixel value of original raster using raster calculator but new layer is not evident

I am trying to create a new raster based on a current raster (w001001 - NVIS) which has one paletted band, with palette values ranging from 1 to 29, with each palette/value representing a vegetation ...
0
votes
0answers
89 views

Why does the SAGA raster calculator fail when used in a Processing model?

I have a problem with the modeler and the saga raster calculator. When I'm using the raster caculator without the modeler it works fine. When I'm using the saga raster calculator in my model I always ...
0
votes
0answers
65 views

Why does QGIS raster calculator create a raster with band values=0?

I have a slope raster (value in %) created with the DEM (Terrain models) tool. I am trying to create a new raster showing the slopes > 15%. In the Raster calculator, I used : (my_raster@1 > 15) * ...
2
votes
1answer
171 views

How to reclassify a raster (tiff) with multiple bands?

i have a raster file containing information about the windspeed average for the year. My purpose is to reclassify the 15 classes based on their rgb-composite. The color is the only information given. ...
2
votes
2answers
126 views

How do I generate a random raster (or probabilistic cellular automaton) in QGIS?

I'm trying to create something like a cellular automaton land cover change model using QGIS, in which cells randomly change land cover based on probabilities determined from various input rasters. ...
0
votes
1answer
35 views

Setting up Raster Calculater for QGIS Python Console: ImportError?

I'm trying to follow the instructions here How to evaluate raster calculator expressions from the console? to set up the python console to to use the raster calculator. I tried: from qgis.analysis ...
0
votes
1answer
58 views

QGIS raster calculator “not equal”?

Is there a syntax for "not equal" in the QGIS Raster Calculator? If so, what is it?
1
vote
1answer
42 views

Re-sizing Raster file pixels

I have 2 JP2 aerial imagery files that are incorrectly sized. They are 100x larger than the other aerial images but correctly geo-referenced (starting x, y co-ordinates). I believe the issue is their ...
2
votes
1answer
69 views

Raster layer calculator

In PCI Geomatic, I have two raster layer.raster1 identified like %1 and raster2 like %2. if (%1 <= 10) then %2 = 60 elseif (%1 > 10 and %1 <=50) then %2=80 elseif (%1 > 50 and %1 ...
4
votes
2answers
114 views

How to find buffer radius around raster cell that covers a defined sum of raster cells?

I want to do a neigbourhood analysis on some raster data. I need to know how big a circle around each raster cell must be to include a certain amount of specified raster cells. Let's say that for ...
0
votes
0answers
79 views

North aspect raster with QGIS Raster Calculator

I have QGis1.8.0-Lisboa and the Raster Terrain Analysis Plugin on Mac/OS. When I want to build a raster layer of an aspect group with the Raster Calculator (e.g.: "aspect@1>=45 AND aspect@1<135" ...
2
votes
1answer
113 views

Change Values of Georeferenced Raster

I am using QGIS to georeference B&W images. I have now done this and would like to set the black surround of the image (as a result of the georeferencing) to transparent but this does not work as ...
5
votes
2answers
351 views

How to calculate the number of cells with a given value?

I have a raster file where all cells have values between -3 and 7, no data value is -9999. Have can I calculate the number of cells with a specific value e.g. 6? Can I use the calculator?
0
votes
0answers
26 views

QGIS save a WMS layer as geotiff (or other) [duplicate]

Can I save a WMS layer as a geotiff (or other) and then, use that file on raster calculator? For example, can I add a wms layer california_geology and then save as image (*.tiff). Import the raster ...
2
votes
2answers
90 views

How to adjust raster size for usage in raster calculator?

I want to make a visibility analysis of planned wind turbines in my region. I have a DEM raster and a polygon describing the possible area where the wind turbines might be set up. People are ...
0
votes
0answers
28 views

Raster Calculator [duplicate]

Could anyone help me with some information on using the raster calculator functionality in the python console within QGIS. I need to apply a mask and compute zonal statistics on a few hundred tif's. I ...
0
votes
1answer
288 views

Rasterize vector layers with different extents into identical raster grids with QGIS

I am working on a quite simple spatial potential analysis using QGIS. I have some ArcGIS knowledge, but I am new to QGIS. My task is to identify the functional inner city of a region based on ...
2
votes
0answers
192 views

ArcGIS Raster Calculator VS QGIS Raster Calculator [closed]

Are there any major differences between ArcGIS Raster Calculator and QGIS Raster Calculator?
0
votes
2answers
177 views

SAGA, GRASS Raster values to null

I want to make the cells which values "1" to null in QGIS with Grass or Saga tools (exactly Saga).
1
vote
1answer
575 views

How to evaluate raster calculator expressions from the console?

How can I execute from the console an expression that should be used with the raster calculator? I'm searching for something like this: qgis.someRasterCalcClass.evaluate("boh@1 + boh@2", ...
1
vote
3answers
1k views

QGIS Raster Calculater Syntax

I am trying to use the raster calculator in QGIS to combine a number of rasters. I want to calculate a mean, this is easy: (raster_1@1 + raster_2@1 + raster_3@1) / 3 I then want to create a max. ...
5
votes
1answer
146 views

Calc bottomline of valleys

Which way do I calculate bottomlines of valleys or even more preceise: which way do I "find" valleys (for example suggested tectonic faults). Sample below shows a height profile (profile from line) ...
1
vote
1answer
303 views

How to add rasters of different sizes with Arcmap or Qgis raster calculators?

I've got 8 rasters all of different sizes. What is the proper syntax, for the raster calculators of either Arcmap or Qgis, that will output a raster that covers the extent of all my data not just the ...
5
votes
1answer
235 views

How to calculate a standard deviation across multiple raster layers?

I have 15 raster layers. Each one shows accumulated precipitation (rainfalls) for the month of April for the same US state during a given year. So, I cover the period from 1997 to 2012. I would like ...
3
votes
1answer
241 views

how can I obtain the areas where my rasters overlap, using Qgis?

I have a bunch of raster files showing the distribution of different species of mammals, and I would like to obtain the areas where they overlap, the areas in whitch more than one species can be found ...
3
votes
2answers
574 views

Normalize raster values to 0-255

I need to normalize the values attained from a band ratio to 0-255. I'm using QGIS. How do I do this? Any ideas?
4
votes
1answer
703 views

How to reclassify in Rastercalc?

I now need to reclassify, I'm using rastercalc... but I can't get the syntax right!! I need that values >0 become 1 I found this example... eq( [relief]@1, [mask]@4, 150 ) so I tried: ( [raster A ...
5
votes
1answer
4k views

How to crop raster layer?

Can anyone tell me how to crop a raster layer in QGIS? I want to make contours from a section of a layer, and including the whole layer will create far more data than I need and slow down the ...
2
votes
2answers
599 views

How to calculate a new raster based on nodata values from original raster, in QGIS?

I'm using the raster calculator from core in QGIS and I need to generate a new tif raster file (mask) from the nodata values of another tif raster file. I tried isnull(), but no luck. Any one can ...
2
votes
2answers
257 views

Is it possible to attain a classified raster with several classes in just one QGIS raster calculator operation?

I'm using qgis' raster calculator and wanted to make a new raster (oraster) from the values of an input raster (iraster). something like: if iraster>2 then oraster=1; if iraster >4 then oraster=2; ...