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Questions tagged [pixel]

In digital imaging, a pixel, or pel (picture element), is a single point in a raster image, or the smallest addressable screen element in a display device. In GIS applications, a pixel may also refer to an imagery layer or other raster data.

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45
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1answer
24k views

Getting pixel value of GDAL raster under OGR point without NumPy?

I am working on a computational model of the abundance of wild pollinators across a landscape. The model itself is complete, and I am now struggling with a post-processing step. I have my GDAL ...
5
votes
3answers
879 views

Can single raster pixel hold more than one value?

Can a single pixel of a raster hold more than one value?
5
votes
2answers
2k views

How to count the number of pixels with a specific value of a .gif file in QGIS

So I have this .gif file that has values from 0-255 but not entirely grayscale. I tried the r.report and it does not work. I also tried the raster calculator like: "myraster@1"= 1 (because I want to ...
5
votes
2answers
119 views

How to sum multi values for each pixel in PyQGIS?

I have a raster layer and a vector point layer. I calculated distance between center each pixel and each point based on @YoLecomte and @mgri, this link and xunilk, this link. For each pixel there are ...
5
votes
2answers
111 views

Knowing the pixel size for a raster before it was resampled

Is there a method to know the exact pixel size (the original size) of a raster “aerial photo”? I have purchased an Arial photo with 10 cm pixel size resolution, and I received a sample of it, but ...
4
votes
2answers
499 views

AWS Sentinel 2 incorrect cloudy pixel percentage

For some tiles with low data coverage percentage metadata and tileInfo contain cloudy pixel percentage value equal 0. Examples: http://sentinel-s2-l1c.s3-website.eu-central-1.amazonaws.com/#tiles/37/...
4
votes
2answers
612 views

Is it possible get pixel value with only PyQGIS and not GDAL?

It seems that gdal can caused in some crashes in QGIS, specific in used for raster layers (such as links : QGIS crashes on close if data was read through GDAL in Python Console or GDAL/QGIS broken ...
4
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2answers
713 views

Understanding raster units

I have a shapefile with several polygons, and I want to convert it to a raster file with 30mx30m (using QGIS 3.2). I am using "Raster > Conversion > Rasterize", and I am having trouble with the ...
4
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1answer
3k views

How do I change the pixel size in GDAL without changing the extent?

I need to change the pixel size of a GTiff in Gdal without changing the extent. When I use gdal_translate -tr xres yres src_dataset dst_dataset It changes the extent. I do not need a rescaling or ...
4
votes
2answers
7k views

Calculate the average of neighbor pixels for raster edge

I have a small raster (or matrix) and I would like to know what is the difference between each pixel and the average of its' 8 neighbors in the case where the kernel window is on the edges and no ...
4
votes
2answers
4k views

Difference between Ground Sampling Distance and pixel size in RapidEye

I am a bit confused about reading technical specifications on RapidEye satellites. I assumed that Ground sampling distance (GSD) and pixel size express the same meaning, while GSD is 6.5 m, and pixel ...
4
votes
1answer
46 views

Updating raster pixel values where they overlap with another raster band

I am trying to replace/update the raster pixel values of band '3' of a Land Cover Map to a new value of '24', but only where these pixels overlap with value '4' of another raster layer. How do I write ...
4
votes
1answer
800 views

Extract All Pixel Values for each band in a Multi Band Raster

I have a few multi band rasters I'm working with, and I need to perform statistical analysis (in another program) on the data. My mentor told me to determine the value for each pixel in each band, and ...
3
votes
1answer
6k views

On a map of the globe that is 1920x1080px, how big would each pixel be?

I heard from one source 21km square, and from another 245km square...
3
votes
1answer
517 views

Getting value of pixel and its 8 surrounding pixels from points using QGIS

I have a point Shapefile layer and a land cover raster layer. For each point, I want to get the value (land cover) of the pixel it falls into and also of the 8 surrounding pixel. Is there a tool in ...
3
votes
1answer
275 views

Getting different pixel depths from output raster when done in ArcMap versus Arcpy?

When I use 'Plus' in Spatial Analyst to add together two 8-bit unsigned rasters (pixel values 0-100) the output raster is 8-bit unsigned (pixel values 0-200) but when I try and do the same thing ...
3
votes
1answer
799 views

Calculate pixel coordinates for each pixel in raster? EPSG:27700 (British National Grid)

I have some Met Office rain radar files (NIMROD binary files). These contain raster data where each pixel is a 1km grid square. I am trying to calculate the geographic position of each of these pixels ...
3
votes
1answer
81 views

QGIS convert pixel location

Is it possible to convert a list of pixel locations (txt file) into lat long? What I have is: (left_x: 137 top_y: 146) (left_x: 175 top_y: 236) (left_x: 182 top_y: 153) (left_x: 185 ...
3
votes
1answer
311 views

Get indices from pixels with a certain value in PyQGIS

I'm working in the Python-Console of QGIS and I have an object form the class QgsRasterLayer. I want to get the indices of those pixels that have certain pixel value (e.g. I need the indices of all ...
3
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0answers
56 views

Rotating orthophoto based on polygon boundary (rotated pixel)?

When I clip an orthophoto using a vector polygon, the resulting pixels orientation is north-up like as shown in the graphic below. I used Global Mapper, ERDAS, Arcmap "Clip" "Extract by Mask", "...
3
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0answers
605 views

How to get pixel coordinates in QGIS georeferenced output map?

using the QGIS Georeferencer GDAL plugin, I can select GCPs (ground control points) on a map (plain raster input map image in a format like PNG or TIF) in an unknown projection and boundaries, and ...
3
votes
1answer
264 views

Identifying pixels with sun glint in a satellite image (for atmospheric correction)

Wondering if anyone knows a way (perhaps objective) to identify pixels that are infected with sun glint in an image. I'm using Hedley's 2005 approach in a python to deglint my image but this approach ...
2
votes
2answers
633 views

Measuring distances from each pixel center (in raster) to each point (in vector) in PyQGIS?

I have one raster layer and point vector layer. I want to measure distance between center of each pixel in raster to each point in vector layer. I extracted x,y center of each cell and added them to a ...
2
votes
1answer
274 views

How big is a MODIS 250m pixel in reality?

How big is a MODIS 250m pixel in reality? This appears to be a question that contains its own answer, but I have several reasons to doubt that the pixel size is actually 250m x 250m: I downloaded ...
2
votes
1answer
389 views

Blurring raster using ArcGIS for Desktop?

I work with this JPG areal photograph and i need to blur this signed blue rectangle only: I tried to decline the display quality in the display layer properties: but it not enough for me, ...
2
votes
2answers
483 views

Is it Possible to Resize the Pixels

I classified this image in ArcGIS 10.3, but my Professor said the pixels are big and I should make it smaller. This is my problem: is there any tool that can use to make the picture grains finer. Or ...
2
votes
1answer
101 views

How to write a single pixel or a line of pixels to GeoTIFF using GDAL/Python

Let's say I want to write a single pixel or a 1D array of pixels (e.g.all at the same latitude) of pixels to a single-band of a Float32 GeoTIFF using the Python GDAL bindings. How can I do so? Or is ...
2
votes
2answers
248 views

What does Zero pixel value in NDBI mean?

NDBI > 0 indicates built up, while NDVI <0 indicates no built up value. What does NDBI = 0 mean?
2
votes
1answer
35 views

Extract maximum pixel value vertex from a raster for a given grid cell without altering the position of the source location in QGIS

I have a 0.5 X 0.5 metre resolution raster. I would like to extract the maximum value points from the raster for every 2 metre square cell. And the extracted points should be in the centre of the ...
2
votes
1answer
183 views

Getting coordinates of pixel from georeferenced drone photo?

I have a problem with geo-referenced photos from a DJI drone. I have the coordinates of the center of the photo and the metadata related to the photo and I would like to know how to go from a pixel to ...
2
votes
1answer
736 views

R How to multiply the values of the raster pixels with the true surfaces of these pixels?

I want to multiply the precipitation values (mm) of each pixel of a raster by the area corresponding to each of these pixels under R. At first, I directly multiplied the raster by the average pixel ...
2
votes
2answers
187 views

How to count pixels in a raster below a given value in PostGIS

The code below works in getting the basic statistics of a clipped raster. I would like to add a metric that is the percent of pixels that are below a given value. I am already calculating the total ...
2
votes
1answer
480 views

Wrong Min and Max Pixel values

I want to convert a raster .tif file into a raster .asc file in QGIS. For this, I am selecting Raster -> Conversion -> Translate option. I am getting the output .asc file. But, both the minimum and ...
2
votes
2answers
1k views

Identifying missing pixels/ pixels with no data value in .tifs

I am looking for a way to identify missing pixels in .tifs. For example, in the attached image there is a row and a column of missing pixels across the image. The no data/ missing pixels after some ...
2
votes
3answers
33 views

Extracting pixel values in different bands for different points giving NAs and not pixel values

I am working with R statistics. And I am trying to extract pixel values for each point in each Landsat bands, however, I am just getting NAs instead of getting pixel values Does anyone have any ...
2
votes
0answers
408 views

Correct resampling method to simulate lower resolution satellite data?

I would like to simulate lower resolution satellite imagery from continuous higher resolution imagery. For example I want to use Landsat derived leaf area index data with a resolution of 30 m and ...
2
votes
1answer
108 views

Get pixel values from a raster using a multipartpolygon

I'm trying to get the mean value of pixels from an NDVI raster, that intersect the geometry of a FeatureCollection, that is a multipart polygon which represents my sample area, but I can't find the ...
2
votes
0answers
258 views

QGIS change pixel size after multiplication in raster calculator

QGIS change raster size after multiplication in raster calculator: I have layer with size 25x25 pixel as you can see in the picture: When I multiple this layer * 0 in raster calculator (I need clean ...
2
votes
0answers
100 views

Accessing cell value of a wms raster served as ol.layer.Image from OpenLayers

Hi I would like to access the value of the raster cell on clicked location (sort of an indentify tool) of a raster displayed in a webapp as ol.layer.Image via mapserver. I have set the .map file of ...
1
vote
3answers
154 views

Converting raster pixels to vector cells?

Is there any way to convert raster pixels to vector cells? I mean each pixel to a polygon. I tried the SAGA tool 'Raster values to points' by choosing cells option instead of nodes option. As a ...
1
vote
1answer
358 views

Linear regression between every 3×3 pixels between two rasters using R

I have two rasters of precipitation and elevation, PPT and ELEV. They have equal number of rows and columns.I want to create a new raster of precipitation lapse rate (GRADIENT) with same number of ...
1
vote
2answers
48 views

Selecting all the pixels in a raster coverage that have a specific pixel value? (in PostGIS raster)

I have a land use map in the format of TIFF. I imported this file as a table in PostGIS using raster2pgsql. The land use file has 7 different classes. How can I select all those pixels that have the ...
1
vote
1answer
2k views

Counting number of pixels using ArcGIS Spatial Analyst?

There is a raster data which contains specific areas separated by layers. My purpose is to count the number of the pixels in those areas. Is it possible to do it in the ArcGIS Desktop 10.5.1 with a ...
1
vote
1answer
376 views

Setting Map Algebra/Raster Calculator's pixel depth

I use Raster Calculator a lot for my work and was wondering if there is a way to set the output pixel depth to a desired value without using Copy Raster tool after I run a calculation, which is the ...
1
vote
2answers
56 views

Cannot read pixel value from DTM raster with QGIS

I am using this DTM: http://ags.cuzk.cz/arcgis2/services/dmr4g/ImageServer/WMSServer?request=GetCapabilities&service=WMS At ArcGIS I am able to ready pixel value of the raster but at QGIS it ...
1
vote
1answer
134 views

Lost pixels during a raster merge with gdalbuildvrt

I'm trying to merge some rasters with gdalbuildvrt in a python script: rasters = glob.glob('/{0}/ndvi_masked/*.tif'.format(path)) gdal_cmd = 'gdalbuildvrt -q -vrtnodata "0" -overwrite {0}.vrt'....
1
vote
1answer
225 views

Calculating area of raster pixel when pixels are different sizes at different latitudes using ArcGIS Desktop?

I have a large raster file of total mangrove cover for the whole globe (obtained from NASA: http://sedac.ciesin.columbia.edu/data/set/lulc-global-mangrove-forests-distribution-2000/metadata). I'm ...
1
vote
2answers
5k views

How import many raster in r?

I have different raster layers, but it is not a mosaic. I want to extract all pixel values, mean and standard deviation for each raster. But I prepared my scrip in r, and I import each raster and ...
1
vote
3answers
449 views

Extracting pixels of raster1 that overlap with raster2 in ArcGIS for Desktop?

I have 2 partly overlapping raster datasets, would like to extract pixels of one dataset that overlap with another dataset. Is there a tool in ArcGIS for Desktop to do this?
1
vote
2answers
429 views

Is there an analog of PhotoShop's “Magic Wand Tool” in ArcGIS Desktop?

I want to interactively select rasters pixels based on it's values and modify them. Here is example of what this "Magic Wand Tool" should do: