8
votes
Accepted
Changing raster calculation values - shorten this script?
What you want is a conditional calculation: return the value of r whenever r and r1 are equal and otherwise set the output to NA.
The cell-by-cell arithmetic operations seem to be fastest. (They are ...
- 69.4k
6
votes
Accepted
ArcPy map algebra equivalent for "any"?
You could sum the rasters and test whether the total is greater than 0.
list_of_rasters = [Raster(a), Raster(b), Raster(c)]
z = CellStatistics(list_of_rasters, "SUM") > 0
- 64k
6
votes
Accepted
Passing additional arguments to ST_MapAlgebra callback?
Additional arguments are passed as the 6th, and so on, arguments, after the custom function signature:
ST_MapAlgebra(b1.rast, -- raster to operate on
1, -- band
'...
- 2,560
6
votes
Arcpy reclassify with function
This is how I would do it (it requires the Spatial Analyst extension which I think you have):
import arcpy
from arcpy.sa import *
arcpy.CheckOutExtension = "Spatial"
ndvi_raster = Raster("...
- 3,737
5
votes
Calculate NDVI using ArcPy Spatial Analyst
I presume you're using ArcGIS Desktop which uses python 2x, not ArcGIS Pro which uses python 3x. Side note: this is one example of why it's important to specify the software you are using.
In python ...
- 64k
4
votes
Map algebra in QGIS
You don't need to write code if you have GDAL installed (if you have QGIS installed that should be the case, but you can install GDAL seperately if you want/need to)
This assumes you want a separate ...
- 20.2k
4
votes
Accepted
Arcpy.Delete_management() not deleting folder?
I think this is an issue with ArcGIS having open file handles on the files in your temp folder.
As discovered in our comments, you could delete the Python variables and then use the Delete tool to ...
- 6,221
4
votes
Identifying row and column location of a raster image using ArcGIS 10.1
The $$RowMap, $$ColMap, $$XMap and $$YMap variables (and some others) are no longer (directly) supported as of ArcGIS 10.0.
You can use it via python:
arcpy.env.extent = arcpy.Extent(0, 0, 10, 10) #...
- 64k
4
votes
Accepted
Adding two rasters using map algebra in ArcPy?
What @Joseph says. The Raster class needs a string containing the path to your raster. You've correctly assigned this to a variable, so you then need to pass those variables to instantiate your ...
- 2,126
4
votes
Accepted
Calculate NDVI using ArcPy Spatial Analyst
Are the red_band_raster and the nir_band_raster values integers? It seems likely that you should move the float() commands around each raster variable call in your equations, and not around the result ...
- 2,010
4
votes
Accepted
Merging two rasters, obtain only highest values, overwrite raster in ArcGIS Desktop?
You can do this just by using the Mosaic to New Raster geoprocessing tool. Just choose maximum for your Mosaic Operator and the new raster will use the high value anywhere that they overlap.
- 1,936
3
votes
Accepted
Changing raster value based on point feature
Add an attribute of 1 to the points and use this for step 2.
Convert the points to raster using the same extent (environment settings > extent> Raster 1 as extent) and same resolution (environment ...
3
votes
Accepted
Raster multiplication script not executing
You're inputting your variables as string. Try without the quotes.
outRas = Raster(in_raster1) * Raster(in_raster2) * Raster(in_raster3)
- 596
3
votes
Accepted
PostGIS raster summation (map algebra)
You will need to write your own aggregate function:
CREATE OR REPLACE function sum_raster_state(raster, raster)
returns raster
language sql
as $f$
SELECT
CASE $1
WHEN NULL THEN
$2
ELSE
...
- 1,187
3
votes
Accepted
Alternative to nested Con statements in python
Not sure if this helps, but I have a script with many nested Con statements, and I find just using indentation helps. For example:
EWR_2015 = Con(
"ministerial_wetlands" > 0,
" ...
- 1,834
3
votes
Accepted
Map algebra in QGIS
One method which I used quite a while ago was to print the standard deviations in the Python Console in QGIS. I would first load all the raster layers (easier if they're kept in the same directory):
...
- 75k
3
votes
Accepted
Getting rid of small objects on raster in ArcMap?
You can use the Majority Filter to remove cells that are surrounded by your green cells. This would also influence the boundary of your dominant green area as this tool works a local level.
In your ...
- 42.6k
3
votes
Accepted
Gdal_calc NDVI for many rasters
Nearly there. Couple of small problems:
You've used the bash syntax instead of cmd. i.e. $ instead of %.
Your --outfile parameter isn't specified explicitly, and looks a bit jumbled.
Try:
for %i in ...
- 2,126
3
votes
ArcGIS Raster Calculator Con-Statement
@FelixIP comment is correct, you need to convert your raster file to a raster object using arcpy.Raster() before using Con().
Here is the code that worked for me:
import arcpy
from arcpy.sa import *
...
- 40.3k
3
votes
Accepted
Creating custom Operation for encapsulating some map algebra using GeoTools?
It sounds like you need jiffle which is contained in the gt-process-raster module. Once you have constructed a Process you can pass in a list of source rasters and bands for it to process in the ...
- 79.9k
3
votes
Accepted
Showing two sets of points from two different fields in QGIS?
Union (geoprocessing) feature make a "union" of 2 dataset (C = A united to B).
Probably you are tring to JOIN two dataset.
Try this:
Go to JOIN settings: (right click -> properties -> Join)
Add ...
2
votes
Adding Rasters with multiple Field Values using Map Algebra in ArcGIS for Desktop?
Use the Lookup function:
Lookup("Raster1", "FieldX") + Lookup("Raster2", "FieldY") + Lookup("Raster3", "FieldZ")
- 64k
2
votes
Accepted
Raster result is different for arcpy.sa CON and arcpy.gp.Con_sa
As mentioned by @Luke, set arcpy.env.scratchWorkspace before running Spatial Analysis tool will redirect that result to scratch workspace.
- 149
2
votes
Accepted
Problem with algebra formulas for work with gdal_calc.py
the test yields either 1 (true) or 0 (false). So you can make an "and" by multiplying the results, and the othe cases using 1-(condition). Here ismy suggestion
B*(A==212)*(B==20) + A*(1-(A==212)*(B==...
- 49.3k
2
votes
Map Algebra syntax
Depends on what you want to create. If you want a raster where your goodslope areas are "1" and the rest are NoData, Con is a good way to go about it:
slope = Slope("elevation") # elevation is the ...
- 1,560
2
votes
PostGis's ST_MapAlgebra rasters do not have the same alignment
To work, rasters passed to the two rasters variant of ST_MapAlgebra() must:
1) be in the same coordinate system. You can reproject one raster to the coordinate system of the other raster with ...
- 2,560
2
votes
Accepted
Looping Map Algebra using Python
You must put a slash after the "work.gdb" on that last line. It is assuming you are saving it as a work.gdbraster file name (e.g. it is appending whatever string "raster" represents to "work.gdb".
...
- 4,489
2
votes
Working with 2 rasters, having different extents but same resolution, in ArcGIS raster calculator?
If you set your environment extent correctly to raster 1, then the extent of the output raster will be that of raster 1, but you will only get data where raster 2 has data (because Value + NoData == ...
- 64k
2
votes
Showing two sets of points from two different fields in QGIS?
If the two source layers have the same fields, you could combine them together using the merge tool.
Using the data you currently have, you would have to rely on the coalesce function to handle the ...
- 39.8k
2
votes
Accepted
What is this Map Algebra expression performing in ArcGIS ModelBuilder?
The Set Null tool takes the following parameters:
SetNull (in_conditional_raster, in_false_raster_or_constant, {where_clause})
which are described in the tool's documentation as follows:
...
- 5,868
Only top scored, non community-wiki answers of a minimum length are eligible