Questions tagged [raster]

Raster is a data format consisting of regular grids of values, usually stored in an image-like format.

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7 answers
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Performing Raster Reclassification in QGIS

Is there a way to perform a reclassify of a raster image in QGIS? In ArcGIS Desktop you can do that in Spatial analyst Tools→Reclass→Reclassify
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67 votes
5 answers
115k views

Clipping raster with vector boundaries using QGIS

In QGIS I would like to clip a raster precipitation layer using an admin boundary layer that is vector data. However the Geoprocessing tools seem to be usable only for vector data. How can I clip this ...
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28 votes
12 answers
84k views

Extracting raster values at points using Open Source GIS?

How can I extract values from a raster by points? I prefer not in Arcgis. I prefer in Qgis or Mapwindow or other open source gis.
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48 votes
5 answers
40k views

What raster smoothing/generalization tools are available?

I have a DEM that I would like to smooth or generalize to remove topographic extremes (chop off peaks and fill-in valleys). Ideally, I would also like to have control over the radius or level of "...
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7 votes
5 answers
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Converting LiDAR data to raster (DEM/DSM) for ArcGIS input?

I was wondering if there is an option to convert LiDAR data (.las) to a raster/grid (DEM/DSM) format that ArcGIS 10.0 can read?
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  • 79
6 votes
4 answers
6k views

Checking if polygon fits inside another polygon using ArcGIS Desktop?

How do I check if one polygon fits inside another polygon? Furthermore how do I automatically check if one polygon fits in other polygons of my shapefile? I have a shapefile with thousands of ...
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  • 71
23 votes
3 answers
16k views

Accessing raster attribute table in QGIS?

I have some Python code that makes Raster Attribute Tables for GeoTiffs using GDAL. In ArcGIS I can see these attribute tables fine and they behave how I like (as classifications) but in QGIS the ...
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  • 1,530
20 votes
1 answer
13k views

Calculating distance to points in QGIS

Is there a way of calculating the distance to the nearest points in QGIS? In ArcGIS Desktop there is a function called Euclidean Distance, which can take an input vector or raster, and generate a ...
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44 votes
4 answers
62k views

Deciding what interpolation method to use for resampling raster data?

Are there hard and fast rules about which interpolation methods are suited to each kind of raster data?
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  • 595
38 votes
5 answers
59k views

Writing numpy array to raster file

I'm new to GIS. I have some code that converts infrared images of Mars into thermal inertia maps, which are then stored as 2D numpy arrays. I've been saving these maps as hdf5 files but I'd really ...
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  • 1,837
4 votes
2 answers
16k views

How to reclass a raster with reclassify grid values in QGIS?

I'm new in QGIS and I'm trying to reclass a raster with reclassify grid values. I want to reclassify by table, however fixed table has only 3 rows and I need some more, but button to add is not ...
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  • 41
6 votes
6 answers
23k views

Deleting polygon defined area from raster layer in ArcGIS Desktop?

Which tool do I use in ArcGIS 10.1 for Desktop to exclude areas covered by vector polygon layers from a raster layer? I want to keep portions of the raster layers that exclude the portions covered ...
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  • 61
30 votes
6 answers
17k views

Splitting raster into smaller chunks using GDAL?

I have a raster (USGS DEM actually) and I need to split it up into smaller chunks like the image below shows. That was accomplished in ArcGIS 10.0 using the Split Raster tool. I would like a FOSS ...
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28 votes
4 answers
85k views

Converting vector layer to raster using QGIS?

In qgis in the raster menu there is an item "convert vector to raster". This behaves strangely - I do not understand how it is supposed to work. I can select a vector file, an attribute and an ...
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  • 845
34 votes
4 answers
62k views

Fully load raster into a numpy array?

I have been trying to check my filters on DEM raster for pattern recognition and it is always resulting in missing last rows and columns(like..20). I have tried with PIL library, image load. Then with ...
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  • 787
5 votes
3 answers
9k views

Iterate through multiple Raster files and compute statistics using Zonal Statistics

I have a large number of raster images. What I'd like to do is to compute statistics on different sections of these raster files using a polygon. I think everyone is suggesting Zonal statistics. ...
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34 votes
3 answers
7k views

How to represent trend over time?

I have a time series of rasters where the cells of each raster represents some value at a certain time. I would like to generate a map that highlights the magnitude of positive or negative trends in ...
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36 votes
5 answers
126k views

Extract Raster Value into Polygon Attribute

I have Raster Data for a State which has Elevation Data in its pixels. I also have Vector layer which has the 300 divisions of State. what I need is, I want to get the average elevation value of ...
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  • 725
13 votes
4 answers
26k views

Clipping raster layer with *raster* mask layer in QGIS

Given two input layers The clip layer - an arbitrary layer (though in my case it's a float 1 band geotiff) The mask layer - a paletted raster in which every pixel is either NO DATA or a single "...
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  • 5,326
12 votes
2 answers
4k views

What is the source of horizontal and vertical striping in USGS DEMs?

When processing 30m and 10m DEM data downloaded through the National Map Viewer from the National Elevation Dataset, we noticed horizontal and vertical striping not only in the produced results, but ...
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  • 2,010
10 votes
4 answers
10k views

Rounding pixel values of raster in QGIS

I have a raster with float number values for example: 2.544459104537964 and I want to round these up to integers. I have seen other posts on ArcGIS like this one but when I use Raster Calculator in ...
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  • 665
22 votes
3 answers
13k views

Performing Raster Noise Reduction and Edge Smoothing?

I have a raster image like this I want to delete the isolated noise point and smooth the edge (say the white single points, and I want the edges of the entity look smooth). How can I do this in ...
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  • 2,195
7 votes
2 answers
3k views

How to de-noise a DSM?

I have created a DEM, DSM, and nDSM from a LiDAR Point Cloud using SAGA-GIS. I extracted the appropriate returns from the point cloud, then converted to grid, and then closed gaps to fill in any ...
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  • 4,129
14 votes
1 answer
18k views

Georeferencing raster using GDAL and Python?

I want to georeference a raster using python and GDAL. My current approach is to call gdal_translate and gdalwarp using os.system and an ugly list of ground control points. I'd really like a way to do ...
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  • 15.9k
47 votes
7 answers
143k views

What are Raster and Vector data in GIS and when to use?

What are raster and vector data in the GIS context? In general terms what applications, processes, or analysis are each suited for? (and not suited for!) Does anyone have some small, concise, ...
34 votes
13 answers
100k views

Getting boundary of raster image as polygon in ArcMap

I have a rectangular raster image in ArcMap. How can I produce a polygon which is just the extent of the raster image? That is, I want to have a polygon layer with a single quadrilateral which is the ...
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  • 3,866
26 votes
3 answers
4k views

Packing Polygons within polygon using ArcGIS Desktop?

I have a Boolean raster. In the grey areas of the raster I would like to fit a given size polygon within a contiguous extent. Basically, I have an irregular polygon, and i would like to "fit" a ...
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  • 925
10 votes
2 answers
13k views

Interpretation of ArcGIS Kernel Density legend parameters

In ArcMap 9.3 I've used Kernel Density to map various incidents, but the resulting shapefile doesn't display any units of measurement. Is there a good, not-to-technical source that would explain in ...
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20 votes
2 answers
17k views

How to extract pixel value counts from a raster in QGIS?

How does one go about obtaining a summary of the counts of cell values within a raster in QGIS? I know QGIS is doing this, in order to provide the summary statistics and histogram in the properties of ...
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  • 303
15 votes
4 answers
25k views

Manually editing raster to improve classification using ArcGIS Desktop?

I have a land cover classification derived from Landsat TM imagery - I created this classification using ENVI. I would like to edit individual and groups of cells in some areas of the classification ...
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  • 10.6k
9 votes
4 answers
21k views

Extracting one band from three band raster in ArcMap?

I'm fairly new to ArcGIS and I get into trouble extracting a single band layer from a raster image .img in ArcMap that I want to use after in zonal statistics. So far, all help I found is to do the ...
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7 votes
3 answers
3k views

LiDAR (.las) to bare-earth DEM: average points spacing and cell size?

I am using ArcGIS 10.1 to generate a DEM (bare earth) from LAS dataset. To accomplish this, I use Las Dataset to Raster tool as described in Esri website. I have read here and there in the web that ...
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  • 1,454
27 votes
3 answers
50k views

Resampling GeoTIFF images to same resolution using QGIS

I have two geotiff images that I would like to resample the same resolution. If I use ArcGIS Desktop this is easy to do but how do I do this using QGIS?
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26 votes
6 answers
16k views

What is Change Detection and performing such analysis with open source tools?

From wikipedia page: Change detection for GIS (geographical information systems) is a process that measures how the attributes of a particular area have changed between two or more time periods. ...
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  • 11k
16 votes
2 answers
16k views

Changing color of raster images based on their data values - gdal [duplicate]

Let's say I have 1 band raster images with Gray Color Interpretation and I want to change their color based on their data values. Data values -1, will be Blue, -0.5 will be Light Blue, 0 will be ...
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  • 397
18 votes
2 answers
9k views

Counting and rasterizing polygon overlaps in ArcGIS Desktop?

How do you take a vector layer with overlapping polygons and turn it into a raster where each cell counts the number of polygons containing that cell? We are looking at polygons of fire burn areas ...
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  • 181
38 votes
8 answers
30k views

Creating shapefile showing footprints of Rasters? [closed]

I have around 1,000 satellite images in tiff format, and I want to create a shapefile which will serve as an index to the rasters. This is something similar to a raster catalog, but I do not want to ...
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15 votes
5 answers
31k views

How to calculate raster statistics for polygons?

how can I calculate sums, averages etc of raster-points (multi-band) per polygon of a vector-layer. I was told that this is called "zonal statistics". I tried that with QGIS first. There is a way to ...
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  • 845
10 votes
4 answers
5k views

Assigning RGB values from Geotiff image to LiDAR data, using R

I have given a Geotiff image and its corresponding Lidar data (x,y,z) in UTM coordinates. I need to merge the Lidar data with the RGB values from the image. That means, at the end, I need to plot (...
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8 votes
1 answer
7k views

QGis Save Raster as Rendered Image

In QGIS 1.9.0 Master, when you right click on a raster in the Layers Panel and select "Save As", you can select the output mode to be "Raw Data" or "Renedered Image". When selecting the Rendered ...
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55 votes
3 answers
21k views

What is Lanczos resampling useful for in a spatial context?

GDAL includes a resampling method beyond the normal mix of nearest neighbor, bilinear, cubic and splines: "Lanczos windowed sinc resampling". I understand that its a convolution filter, but unlike ...
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  • 16.1k
44 votes
2 answers
50k views

How can I convert data in the form of lat, lon, value into a raster file using R?

I have a data set of values over a km grid in the continental U.S. The columns are "latitude", "longitude", and "observation", e.g.: "lat" "lon" "yield" 25.567 -120.347 3.6 25.832 -120....
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  • 1,863
48 votes
8 answers
52k views

Using continuous color band for raster legend in QGIS composer legend?

I'm looking for a way to insert continuous colour legend for a raster layer. I managed to create discrete symbols with values along the bar, but I would like to have a continuous bar with some values ...
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  • 771
30 votes
2 answers
65k views

Joining several raster files using QGIS?

I'm new to QGIS. How can I combine multiple raster layers into one layer? The raster images are of different areas with very little overlap. The goal is to bring numerous town plats into one ...
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14 votes
9 answers
16k views

Aligning two non-coincident equi-resolution raster grids in ArcGIS Desktop?

I have two rasters: a digital elevation model (DEM) and a Landsat band. The grid resolution of both is 30 m, but the grids are not coincident (see image: the dark raster on top is the DEM; the light ...
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  • 1,358
12 votes
4 answers
6k views

Comparing two Digital Elevation Models (DEMs) from LAS files?

I have two LiDAR files (.las), one is original let's say with X points. And the other is copy of the first .las file but with Y points, where Y is less than X. Now, I want to compare the Digital ...
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14 votes
4 answers
13k views

Using polygons to apply unique value to all raster cells within those polygons?

In ArcGIS 9.3, I have a raster file that I would like to "mask" with polygons, giving a single value to all the raster cells that overlap the polygons. How can I do this? Here's a screen shot, ...
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  • 397
11 votes
1 answer
11k views

How to reproject a raster file in QGIS with datum transformation?

I want to reproject a tiff raster file from projection A (ETRS89/UTM Zone 32) to projection B (DHDN/Gauss-Kruger zone 2). The two projections have a different datum so I have to use a datum ...
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  • 6,039
9 votes
3 answers
11k views

Finding nearest raster cell value based on vector point?

I have two layers in ArcGIS: One is a vector point and the other is a raster layer. I want to append the value of the raster data grid to the vector point. The problem is the vector point is away from ...
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  • 2,195
8 votes
2 answers
10k views

Exporting DEM-derived rasters to CSV from QGIS?

I have been able to import into QGIS a set of raster topographic maps and the associated DEM raster maps. It registered the two for me. From there I have calculated the associated slope raster map. ...
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