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.

43 questions with no upvoted or accepted answers
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61 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", "...
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0answers
640 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
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1answer
270 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 ...
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0answers
43 views

Scatter matrix using pandas does not reset any graph

I would like to find the statistical correlation between all the pixels of an image in relation to the bands. In my case 7. from osgeo import gdal from osgeo import gdal_array import numpy as np ...
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3answers
35 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 ...
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429 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
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1answer
115 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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0answers
271 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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0answers
101 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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1answer
17 views

Cannot get number of max pixels in Google Earth Engine

I have a code that calculates the max number of pixels among all the rasters it retrieves and then creates new imagecollection with only rasters that contains rasters in the size I want. For some ...
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1answer
38 views

Count the number of pixels according to their value using for loop

I have script that does the enxt procedures: create imagecollection from Landsat7 clip the images according to specific geometry and calculte NDVI for each one filter the rasters according to the ...
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20 views

Reprojection problem with Rasterio

I have already processed so far NDSI map by using Rrasterio, NumPy, os and matplotlib.pyplot for plotting the data. Now, I would like to eliminate permanent ice from NDSI map. I am facing one major ...
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26 views

Simultaneous raster downsampling/downscaling and upsampling/upscaling for false accuracy minimisation

I want to have a raster stack of two different resolutions. One is from VSNIR and one from SWIR sensors (hyperspectral). The VSNIR has a resolution of 25 cm and the SWIR of 80 cm and both data have ...
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31 views

Convert pixels to coordinates

I have a vertical image with size (W,H). I have info about the coordinates in decimals of the the upper left and bottom right (Lat1,Lng1,Lat2,Lng2). I have the Ground Sample Distance (GSD) of the ...
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1answer
38 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
75 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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25 views

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
58 views

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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241 views

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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150 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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51 views

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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96 views

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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178 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
210 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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383 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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0answers
153 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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186 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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203 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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0answers
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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0answers
132 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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218 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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0answers
82 views

Where does the snapshot command take its pixel samples from?

I'm using the snapshot command in QGIS with a horizontal extent from 0 units to 24 units to create an image with a horizontal resolution of 4 pixels. Are the output pixels located at 3,9,15,21 (...
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80 views

How to integrate set of neighboring pixels in raster dataset?

I generated peaks of tree crowns as an individual pixels from DSM dataset, but there are some trees that have more than 1 peaks. I would like to integrate them based on the threshold value, for ...
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0answers
75 views

Choosing pixel size when projecting raster from geographic to projected coordinate system

I have a raster showing animal abundance (straight count) in all of Canada. The raster was created unprojected in GRS 80 with a pixel size of 0.0833 decimal degrees. I was ask to project this raster ...
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69 views

Mosaic DEM has large pixel when displayed in ArcMap?

I created a mosaic dataset in ArcMap 10.2 from tiles of ASTER DEM's at 30m resolution. I am attaching the image of what my export looks like. You can see that there are extremely large, alternating ...
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1answer
22 views

GDAL Sentinel-1 pixel size

We know that fields related to "Geotransformation" and "projection" are empty when one tries to access these information using gdal on Sentinel-1 (at least the GRD products). I normaly use: gdal....
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1answer
27 views

Why does Earth Engine report Sentinel-2 pixel depth as 16-bit when it is 12-bit?

When accessing Sentinel-2 through Earth Engine search bar, the info page that pops up reports the bands as UINT16 when in reality they are 12-bit. Am I interpreting this incorrectly?
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13 views

No Data Value through Pixel Inspector in ArcMap

I have a raster that represents temperature on a global scale derived from satellite data. Initially it had pixels in the ocean assigned -9999. After I used SetNull tool to eliminate them they show up ...
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0answers
24 views

OpenLayers3 map.forEachLayerAtPixel bug

Hi I'm working with OpenLayers version 3 and using method map.forEachLayerAtPixel(). The problem is I usually work on big screen and now I have switched to my laptop with smaller one and suddenly ...
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0answers
37 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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0answers
128 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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239 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 ...