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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157 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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47 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
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 ...
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1answer
206 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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40 views

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
48 views

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
707 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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367 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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145 views

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 ...
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179 views

NDVI raster to polygon in QGIS

I have an NDVI raster created through a Parrot sequoia and Pix4D. When imported into QGIS 3.0.2 it is shown as a singleband gray render type with a range of -0.355826 to 0.905562. I want to create ...
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1answer
333 views

Cloud mask using pixel_qa

I need to create a cloud mask using the pixel_qa band, this is the code that I have so far: var city = ee.Geometry.Point(9.15, 45.18); var landsat8 = ee.ImageCollection('LANDSAT/LC08/C01/T1_SR') // ...
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256 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 ...
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1answer
357 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 ...
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2answers
246 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?
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1answer
229 views

QGIS - Issue with No Data Value Pixel is changing only in header of ascii

I have changed the No Data of a raster Forest.asc into No data = 0 using Raster -> Conversion -> Translate option in QGIS. So, when I add the output raster layer Forest_1.asc in QGIS and check for ...
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1answer
477 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 ...
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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 ...
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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 ...
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142 views

Sieve function in QGIS not working properly? [closed]

I am trying to eliminate single pixels in a (binary) raster with the gdal_sieve function. However, regardless of the settings I choose (I tried threshold=1, 2 and 70 and pixel connection 8), the ...
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1answer
853 views

how to get every images's pixel values of “ImageCollection” in GEE

I create a Sentinel-2 cloud free mosaic image with Google Earth Engine and exported the image to an Earth Engine asset. I know the image that I exported was composed by several images that taken at ...
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1answer
432 views

Recovering pixels at intersection of polygon and raster image in PyQGIS?

I am beginner in PyQGIS. I would like to recover the pixels that intersect with my shapefile (polygon) using a loop for ... apparently, the loop is incorrect (no result). Below the code from ...
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2answers
124 views

Extract areas from DEM between 100 meter contours using r.report or similar tools

I'm trying to extract the total area within the same altitude range in a DEM. As example, I'd like to know the total area between 800-900 m asl of a DEM. Using r.report I've just got this: How can I ...
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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/...
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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 ...
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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 ...
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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 ...
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200 views

Pixel values change after clipping a raster layer

I'm trying to evaluate mean temperatures for the distribution area of European fish species. Therefore, I downloaded the E-OBS data set for mean annual temperature in Europe (0.25 deg. reg., "TG"), ...
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1answer
3k views

Converting coordinates to pixels with out losing points

I'm trying to convert coordinates from lat/lon into pixel but I lose points in this process. The code that I'm using is the following: from matplotlib import pyplot as plt import numpy as np import ...
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1answer
733 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 ...
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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 ...
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1answer
89 views

Why does QGIS crash when extracting pixel values by GDAL?

In below code I want to print pixel values, but when run in QGIS python console QGIS software crashes and closed! what is the problem? from osgeo import gdal import numpy import struct def ...
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30 views

a kind of intersection to compare color areas of 2 layers (ol4) - but how?

Hopefully anyone can point me to something to get this done ... cause its just a WMS and not a webGIS (ol4) Imagine: We have two tiled choropleth-maps and we want to compare areas of both. They have ...
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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 ...
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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 ...
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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 ...
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233 views

IDL - Cropping GeoTiff with IDL (no Envi)

How can I crop a GeoTiff (EPSG:4326) in IDL by using pixel coordinates, and then saving the cropped files with the correct georeferencing? I assume I have to re-set the information in the ...
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604 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 ...
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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 ...
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1answer
361 views

raster map layers squished [duplicate]

I am new to GIS software. I've played with Google earth a bit and am familiar with downloading Canadian topographic maps. Anyways, I've been playing around with qgis. I have imported a few ...
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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 ...
3
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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 ...
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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 ...
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1answer
421 views

Applying MODIS Pixel Reliability and Vegetation Index (VI) Quality mask for MOD13Q1 using ArcGIS Desktop?

I have some sets of MODIS MOD13Q1 data sets during March and December for year 2000 to 2015. I need to extract the NDVI and EVI for those two months from the entire 15 years. How do I apply the ...
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1answer
43 views

Finding value of peer to peer pixel in another raster layer with same pixel size, coordinate and location from attribute table?

I have two raster layers with same pixel size, location, coordinate and time. I need to know what the value of defined pixel in one layer is in same location (pixel) in another raster layer. The ...
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0answers
127 views

Tool in ArcMap for capturing ROIs of same size?

I'm trying to run supervised classifications and need all ROIs to be the same size. I'd like to capture the ROIs in ArcMap and so far can only find a tool which allows you to draw your ROIs by ...
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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, ...
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1answer
73 views

Landsat 5 image processing

I am working with Landsat 5 images in UTM-WGS84 using the Qgis 2.14 software. I need to obtain the XY pixel coordinates with their ND and to extract them in an Excel list. How I can do it?
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214 views

Pixel sizes, cartographic scales and maps

In spite of being a widely discussed topic, I have not been able to find the complete answer to my concerns regarding scale's use in maps preparation. I am interested in finding in the relationship(s) ...
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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 ...
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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 ...