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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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 ...
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1answer
29 views

Extracting pixel values for specific point locations in WGS 1984 / EPSG: 4326 image

I have a remote sensing image with GCS WGS 1984 / EPSG: 4326. I need to extract pixel values from this image which corresponds to specific point locations. For that purpose, I defined these ...
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1answer
54 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 ...
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1answer
52 views

Raster calculator - problems with syntax

I have a raster layer with values ranging from 0.00597303 to 0.102894 and I want to assign specific number representing a group to specific range of values: Group 4: x >= 0.1 Group 3: 0.01 <= x ...
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1answer
40 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 ...
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Getting stripe across tiles without buffering image?

I am new to geotools. I need to get a horizontal stripe of bytes from the image data without buffering the whole image. I've looked at the various envelopes and pretty sure I could use just ...
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1answer
106 views

Calculating the distance of each pixel in a raster from a point in PostGIS [closed]

I have a raster in PostGIS and a table of points. I want to calculate the distance of each pixel to each point. How can I do that? For example, if 9 pixels and 3 points, then I want to calculate 27 ...
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1answer
65 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 ...
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2answers
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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 ...
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28 views

delete pixels intersecting vector border

I have a two files : vector file : polygon (red) raster file : got by clipping a raster file using this vector file (Green) I want to delete pixels that intersect with the vector border (I want to ...
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1answer
54 views

Wrong masked pixels

I am new in GEE, and tried to run a simple code to mask cloud pixels. However when I added the image selected with my filters I saw that the result of the cloud filter are empty areas, as shown below: ...
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1answer
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Explanation of reduce.count() function in Google Earth Engine

Following the indication on Calculating number of pixels in polygon using Google Earthy Engine? I wrote this script: var gfc =ee.Image('UMD/hansen/global_forest_change_2018_v1_6'); var lossyear = ...
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Is there a way to interpolate lost data/lost pixels caused by cloud and cloud shadow masks in Google Earth Engine? [duplicate]

I'm sure cloud and cloud shadows have been, time and time again, a frustrating problem. Usually after masking the two, I composite multiple images (in a set time interval e.g. 2015-2016, months 6-8) ...
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1answer
33 views

Obtaining pixels between 2 raster layers (border)?

I have a rasterStack obtained from a stack of 3 raster layers by: image = stack(A, B, C) I would like to calculate the distance between the pixels of layer A and pixels of layer C. After ...
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Calculating pixels coordinates from lat/lon

I'm trying to develop a WPS that would print maps to images and PDFs. I don't want to use Mapfish because of its limitations, and because of some customization I need to add to the printed maps. My ...
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1answer
106 views

Calculating distance between point and selected pixel in R?

I would like to obtain the distance between a point and a selection of pixel on raster image. Here the process: I read my JPEG image and extract colors I want: img.raster<-stack(***) names(img....
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1answer
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Calculating distance between each pixel of rasterstack image?

I am new on R and I have an image of class "rasterstack" of only 3 colors: Red, Green and blue as illustrated: I use this function: image = stack(img.red, img.green, img.blue) I would like to find ...
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1answer
45 views

Using GDAL Warp results in odd pixel sizes and gaps

I am mosaicking one meter and three meter rasters to two meters in Python with GDAL Warp using the following code: cl_string = "-of GTiff -co COMPRESS=LZW -tr 2 2 -tap -r near -overwrite \ -multi -wo ...
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3answers
109 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 ...
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1answer
197 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 ...
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1answer
57 views

Creating raster with custom values? [closed]

I have a problem: I need to create a raster with all pixels values = 0, but one of these pixels must have the value = 1. This pixel has especific XY coordinates related to an in situ station. I need ...
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2answers
146 views

Calculate 16-bit elevation values from a 32-bit RGBA image?

Say a single-band 16-bit (UInt) raster with values representing elevation (meters) must be converted to a 32-bit RGBA PNG image (8-bits/band) for use in a web application. The image dimensions must be ...
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1answer
48 views

Obtain pixel coordinates of an image

I'm working with a tiff image in arcgis projected in UTM 33N and I need to obtain pixel coordinates of a specific point in the image with known metric coords (UTM 33N). How can I get them?
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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", "...
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1answer
38 views

Does the MODIStsp package computes the QA's and eventually corrects the bad quality pixels?

I am using R's MODIStsp package for downloading MOD11A2 time series products. While executing the command it was written that QA's were computed. Several files were created, LST_Day_1km, QC_Day, ...
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1answer
130 views

Using raster stack function time in R?

I successfully ran a function over a smaller test raster stack (48 layers) in about 30 minutes but cannot run it over my large stack (1462 layers). The last one I tried over the large stack ran from ...
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100 views

Clean up pixel noise from raster in ArcGIS

I have this raster. It has some pixels near the main objects, this raster is a product of a classification. those little pixels have the same value of other big objects, so I cannot just reclassify. ...
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0answers
34 views

ArcGIS - Count pixels in two overlapping rasters that have the same value?

I have two raster with five classes each one (each class from 1 to 5 value), they have the same shape and are in the same place, they are in teory "alike", but there are subtle differences between ...
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2answers
260 views

Getting all pixel values from raster image in ArcGIS Desktop?

I am using a CHIRPS raster image on ArcGIS 10.6 and there is no attribute table, I need the pixel values as it is the individual rainfall data for the stations to perform further statistics on. How ...
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1answer
79 views

Pixel count on AFR Raster in ArcGIS?

I have this kind of raster which has no pixel count in his attribute table. I'd like to calculate the pixel count by class: These are the raster's properties
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How to get the area of the pixels of a raster in Africa Lambert Conformal Conic CRS in R

My question has been previously asked here (R How to multiply the values of the raster pixels with the true surfaces of these pixels?), I have to multiply the precipitation value of each cell by the ...
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1answer
45 views

Converting proximity from PIXEL distance to GEOmetric distance in QGIS

I used the Raster>Analysis>"Proximity (Raster distance)" tool in QGIS in order to create a raster of distances to a particular value in another raster. This is the same sort of thing someone might do ...
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2answers
31 views

Eliminating single raster pixels of flow distance raster in ArcGIS Desktop?

I want to clean up a calculated flow distance raster and need some ideas on how to do it. As you can see in the picture, there are some pixels along streets and rivers (gray) that show connection (...
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0answers
303 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 ...
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1answer
28 views

How to find if a pixel is entirely within another pixel when comparing for example two GeoTIFF raster maps? [closed]

Using GDAL and/or Python Red: GeoTIFF raster Map layer 1 Blue: GeoTIFF raster Map layer 2
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Color different of two Sentinel 2A (L1C) images from the same sensing date

i'm new to this GIS Q&A websites and remote sensing as well, so sorry for this too basic question. It's about my Sentinel 2 (Level-1C) images. I downloaded 2 images with the same sensing date (09-...
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116 views

Getting fractional count of pixels in raster map using QGIS?

I have a raster map consisting of 22 land cover classes (LCC). Each pixel is 300 x 300 meters in dimension and contain one of the 22 LCC. I need to make 1 km x 1 km cells in the parent grid and count ...
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1answer
89 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 ...
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1answer
195 views

Extracting pixels in multiple rasters based on the values of another raster's pixels for time series analysis

I'm working with 52 rasters of a specific region over a period of one year in python. I also have a mask raster of the same area that is a binary color (250 black pixels for disparate areas of ...
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1answer
340 views

Filling no data value in raster using ArcGIS Desktop?

I have a raster with no data values, I want to give them values according to values around them. If a no data pixel is surrounded by 8 pixels whose values are 1 then the no data pixel should adopt ...
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1answer
120 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'....
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0answers
121 views

Mapping pixel coordinates to lat lon

For a deep learning project, I trained a YOLO based model to detect objects on satellite images (from spacenet dataset; epsg:4326). However, as the Darknet only takes JPG/PNG images as input(to the ...
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1answer
45 views

Extracting pixels from polygonal geospatial region of set of map tiles and/or set of GeoTIFF files?

I need to create a script, probably JS or Python, to perform the following: I have a polygonal region -- no "holes", and always fully convex -- for which I need to extract the pixel data from one of ...
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2answers
162 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 ...
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1answer
189 views

QGIS 3.2 - Poor conversion from high-resolution vector to raster

I have a shapefile with polygons with several sizes, and I want to convert it to a raster with 30mx30m pixel resolution. Although I was able to obtain the raster with the pretended resolution (using ...
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0answers
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Saving Style as SLD in QGIS but after reloading unit changes from map units to pixel?

I have a style I am saving in QGIS (2.18) as an SLD. After reloading the Style onto the layer the ouline width changes to pixels instead of map units. I even checked the .sld in notepad and the uom-...
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1answer
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Can I change the pixel sizes in a world file?

I start with a dataset that has projection WGS84 and pixel size 0.000274658203125 degrees/pixel. I run gdal_translate to convert it to a PNG: gdal_translate dataset.tif output.png -of PNG -ot byte -...
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2answers
517 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 ...
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0answers
325 views

Extract pixel values at given point dataset and if masked find the nearest pixel value

I need to extract the values at each pixel foe a feature collection from an image and if they are masked the value at nearest pixel, my feature collection is named table and the image collection I am ...
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Prevent pixel doubling for a mobile display - OpenLayers

I'm programming an OpenLayers (4.6.5) map with a layerswitcher in order to switch between my different layers. On mobile, the display of my layer is blurry, OpenLayers is doubling pixels and I don't ...