Questions tagged [raster]
Raster is a data format consisting of regular grids of values, usually stored in an image-like format.
2,258
questions with no upvoted or accepted answers
17
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Parsing file format for attributes in Raster Product Format (RPF) maps and imagery?
I'm trying to implement an open-source NITF reader (using only java, no external libraries such as GDAL or NITRO), and its mostly going OK. However I'm having trouble understanding the RPF extensions, ...
13
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0
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550
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Remove reference to raster layer object PyQGIS
I am developing a plugin to load a set of raster files on QGIS. When there is a large number of files to be loaded, the main UI freezes. So I use QgsTask to move the creation of raster layers to a ...
8
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0
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116
views
Referencing an output in an expression in process modeler
In the process modeler, I'd like to reference an output of a previous step as one of the parameters of an algorithm. In this case, the previous step was clipping a large raster and I want to use the ...
7
votes
1
answer
2k
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Setting CRS of raster to EPSG 3035 using R
I am trying to set the CRS of a raster file with the following code:
library(raster)
r<-raster(xmn=0,xmx=10,ymn=0,ymx=10)
crs(r)<-CRS("+init=epsg:3035")
The warning message is:
...
7
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0
answers
268
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Identification of roof peaks on a Raster in Qgis
I am trying to map all the flat roofs of a city. After processing my data I have a huge raster with the zones that are flat (=1) and not flat (=0).
I can overlap the roof polygons over this raster and ...
7
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0
answers
537
views
PostGIS issue with ST_Clip?
I'm trying to clip a raster using a polygon but I end up with a result that doesn't seem right and where some raster pixels are outside the polygon used for the clip.
See image below where polygon is ...
7
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0
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874
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Cellular Automata Markov for forecast LULC in R software
I would like to forecast land use changes by implementing the Cellular Automata (CA) Markov Chain models in R software.
I have the classified LULC maps from 3 times periods (1992,2003,2014), and also ...
7
votes
1
answer
2k
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Crop raster based on another raster R
library(raster)
How can one clip one raster based on another raster?
RasA:
class : RasterLayer
dimensions : 459, 533, 244647 (nrow, ncol, ncell)
resolution : 10000, 10000 (x, y)
extent ...
7
votes
0
answers
670
views
Using QGIS' "network protocol" to import data from OPeNDAP?
After looking at the OPeNDAP documentation
I assumed I could import data into QGIS by downloading the .ascii file OPeNDAP generates. However the downloaded OPeNDAP .ascii doesn't seem to be compatible ...
6
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0
answers
52
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Adding raster value with specific equation using ArcMap
I am trying to develop a raster layer with the interference of streetlight in this example:
As you can see there are multiple buffer rings around a point layer. I actually want to transform this ...
6
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0
answers
691
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Circular focal means with raster and NAs
I am trying to understand circular focal means using rasters having NA values. I made a couple of scenarios to better understand how to combine weight matrices and functions to summarize values. I am ...
6
votes
1
answer
503
views
Added raster layers with PyQGIS do not show up
I have a list ("datList") with names of raster layers which I want to add. When I add raster layers in the Python Console everything works fine:
for da in datListe:
layerDir = "C:/[...
6
votes
0
answers
88
views
Robust formula to get row,column of raster given X,Y
I'm looking for a robust method to get the row and column of a pixel in a raster, given the coordinates of the origin and the cell spacing. This seems like a problem with an incredibly obvious ...
6
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0
answers
86
views
Creating Raster that sums up input polygons using QGIS?
I am using QGIS and I have a shapefile with buildings. From these buildings, I have made a Buffer with variegating radius. The Buffer also have data about the demand for Parking spots for each ...
6
votes
1
answer
194
views
Calculating accumulated walking pace from starting location outwards using R?
Goal
In R, I would like to calculate an accumulated cost surface around a starting location, with the cost representing the time (say, hours) to walk from the location outwards in all directions (say,...
6
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0
answers
1k
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Add color palette to grey-scale land cover GeoTIFF
I have a single band grey shade tiff image which does not have a a color palette associated with it. I need to open up the symbology and assign a color to each unique landcover class.
I am looking ...
6
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0
answers
1k
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Correctly handling climate projection data with R
EDIT: An example setup can be found here: The main file is extract_cordex.R
I need to analyze climate data as part of my thesis, however I am not particularly trained in working with climate data and ...
6
votes
0
answers
594
views
QGIS Align Rasters how to retain pixel values?
I am attempting to align and then merge a number of rasters of the same resolution and extent, but where the pixels are slightly misaligned (creating small gaps when merged). This works fine using the ...
6
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0
answers
293
views
Building raster (population density) dependend diagram in QGIS
I'm using QGIS and trying to solve the following problem.
I got 2 layers:
population density raster
point layer with the information about number of people could be hosted/served etc in this points.
...
6
votes
0
answers
1k
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Can extracting raster values work in polygons' CRS without raster resampling?
I am trying to extract raster values using polygon layer with different CRS. Raster is in WGS84 (EPSG:4326) and the polygons in UTM (EPSG:23031).
1. If I want to work in the projection of the ...
5
votes
1
answer
412
views
Slow retrieve PostGIS raster value through ST_Value
I have a PostGIS DB containing a set of daily raster data from 1981 up to 2021. The inserted raster tile size is 83x90.
Problem: I wanna query the data through ST_Value for a specified Lat Lon, ...
5
votes
1
answer
250
views
Optimizing pixel extraction from GeoTiff using Python
I am creating IDF Curves for work using python and 30-minute rainfall rate rasters. There are 24 rasters per day and about two decades worth of data. I basically input lat/lon coordinates and my ...
5
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0
answers
70
views
Same LiDAR data but different results in ArcMap and eCognition
I have generated raster layers based on LiDAR Number of Returns in both ArcMap and eCognition but the results are quite different.
I ArcMap I used LAS point to Statistics to Raster Tool, in the ...
5
votes
0
answers
136
views
Setting default raster statistics extent in QGIS?
I recently found the setting in QGIS to rescale raster symbology using the current extent, which is really handy (Layer styling > Min/Max Value Settings).
My question is - can the default extent be ...
5
votes
1
answer
217
views
Aggregating multiple rasters within a polygon in PostGIS
I have several raster tables in PostGIS (four in fact but in this case let us assume there are just two) - same cell sizes, same alignment but with different types of value (e.g 3d_pot, 3d_area). ...
5
votes
0
answers
1k
views
Error using 'Clip raster by mask' in QGIS v3.8.2
I am attempting to clip a raster to a shapefile boundary (country boundary, 1 polygon) using the 'clip raster by mask' tool in QGIS v3.8.2.
Both layers are in WGS84, so projection mismatch shouldn't ...
5
votes
1
answer
826
views
Merging many rasters with Python script within QGIS using GDAL?
I have many rasters that im trying to combine in order to produce contours. They are in the .bil format so I understand that i need to translate them using gdal first but none of my attempts have ...
5
votes
0
answers
260
views
Finding Raster Pixel Neighbors using GDAL?
I'm new to GDAL Python, and I'm working on a little recursive algorithm which requires finding the neighbors of a a pixel on a DEM raster. I've been able to do this by creating a little PixelLite ...
5
votes
0
answers
538
views
Could not allocate required memory for image
I'm trying to export a 24k image (export set to 1650DPI) using the "export as image" function but I keep getting the "Could not allocate required memory for image" warning.
I don't understand why ...
5
votes
0
answers
957
views
Merging two overlapping rasters
There are two rasters A and B. A is smaller but within B and since A has more up-to-date pixel values, I was able to merge A and B with "Mosaic raster layers" tool in QGIS which replaces B pixel ...
5
votes
0
answers
202
views
QGIS rule based symbology for rasters in Atlas?
I'm making species distribution maps and have got the Atlas working perfectly using a polygon layer to show the quarter degree grid cells for species observation records. I have ~ 250 species.
The ...
5
votes
0
answers
321
views
Problem with encoding when clipping raster
I am using QGIS 2.18 on a Linux Mint computer using UTF8.
I downloaded solar radiation raster data from PVGIS. The files are encoded as us-ascii (according to the linux command tool file -bi).
Opening ...
5
votes
0
answers
534
views
QGIS Zonal Statistics for polygons is missing results?
I am carrying out an analysis using QGIS 2.14.1 where I am dealing with point data that have been randomly displaced by either up to 2 Km or 5 Km. I have generated a buffer of the appropriate radius ...
5
votes
0
answers
355
views
Mapcache zooming problem
I am using mapcache for caching map raster data. Everything works fine except the map zooming, because at the some zoom level i am getting pink tiling images.
This is my mapcache xml file:
<?xml ...
5
votes
0
answers
678
views
gdal_translate slightly changes output pixel values
I have used this batch script
for /r %%g in (*.jp2) do gdal_translate -co COMPRESS=LZW -co
NUM_THREADS=ALL_CPUS %%g %%~dpng.tif
to recursively convert all my .jp2 files in .tif files. However, the ...
5
votes
0
answers
115
views
Why do I get a memory allocation error when selecting rasters by ID in PostGIS?
The Problem
I have about 256000 tiles in a table of GDEM v2 at 1 arcsecond resolution. I'm on an Ubuntu server running Postgres 9.5.5 and PostGIS 2.2. The table has a GIST index on the convex hull of ...
5
votes
0
answers
178
views
QGIS integer raster stats calculation error
I am comparing two raster temperature files generated from two different sources that use different algorithms. One of them is provided as a floating point (temp(C)) and the other is integer (temp(C)*...
5
votes
1
answer
203
views
ArcGIS Online Image Offset
I have three geo-referenced images of a museum layout that I have been able to offset by "x" number of meters in ArcScene and ArcGIS Pro. I want to publish the three images online and have ...
5
votes
0
answers
438
views
Creating polygons from points using lines as barriers
This question is similar to a previous post where the member asked if it were possible to create Theissen (Voronoi) polygons from lines:
Creating Thiessen (Voronoi) polygons using lines (rather than ...
4
votes
0
answers
1k
views
Cloud-Optimized GeoTIFF overlay on Leaflet?
I want to load external Cloud-Optimized GeoTIFF files onto a Leaflet map as overlays, and manipulate the colors based on user input. I've found examples online that appear to to this exact thing, but ...
4
votes
0
answers
373
views
Plot polygon on rasterio window
I'm trying to plot several polygons on a raster. Several posts suggest to use matplotlib and descartes like this one: Plot shapefile on top of raster using plot and imshow from matplotlib
My polygons ...
4
votes
1
answer
362
views
Dealing with no-data values in raster calculator of QGIS
I am trying to patch two rasters with raster calculator but I am not finding the way to work with no-data values.
Lager@1 has some information I need as first option, this has as no-data -9999 (...
4
votes
1
answer
275
views
Extract pixel values in raster stack using shp
I am using the following code to extract mean pixel values over an area represented by a polygon:
mean<-lapply(S2_stack, FUN=function (S2_stack) {data.frame(mean=extract(S2_stack, polygons2, fun=...
4
votes
1
answer
203
views
Loading raster to R from PostgreSQL via pgGetRast takes a lot of time
I wrote R code in R Studio to load a raster (stored in PostgreSQL) to R. The database is stored here: C:\Program Files\PostgreSQL\
The following versions are installed on the computer:
R version 3.4....
4
votes
0
answers
1k
views
How to store large time series of raster images
I've got a large time-series of rasters, derived from satellite images. Each raster is about 2000 x 2000 pixels, and I've got about 10,000 individual images. I'm trying to work out what the best way ...
4
votes
0
answers
585
views
Aligning two raster layers in QGIS?
I am teaching myself GIS in baby steps, I recently acquired aerial imagery (employing RGB and NIR-GB sensors) using a small UAV with the intent of generating a map in a small plot of land. After ...
4
votes
0
answers
284
views
Stretch to MinMax results in blank render output in QGIS?
I am a new QGIS user, and I can't figure out if I encountered a bug.
If I have a multi-layer image, and "Multiband color" -> "Stretch to MinMax" selected I get the following behaviour. QGIS takes a ...
4
votes
0
answers
143
views
LasDatasetToRaster does nothing to the Raster Layer
I have been trying to figure out how to clip and rasterize a LiDAR map file programmatically (Not through arcpy) I use C# but read many languages. So far I have been able to access and assign the LASD ...
4
votes
1
answer
1k
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How to "mosaic" rasters and keep attributes
I have numerous individual 10m Raster files (with both quantitative and qualitative data) for each state and need to combine them into a national dataset.
However, when using a mosaic it seems that ...
4
votes
0
answers
1k
views
How to avoid "Unable to compute a transformation between pixel/line"?
I am trying to re-project from Equi-rectangular to the NASA global EASE grid (Equal Area Scalable Earth) grid 1383 586 with a ~25 km cylindrical projection (ESPG=3410). The file is provided as HDF5.
...