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1500 questions
29
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3 answers

Learning resources for GDAL?

I quite often get stuck trying to solve particular problems, or getting syntaxes right. Apart from the details provided in the links on GDAL Utilities, does anyone know of any 3rd party resources/manuals explaining it in a bit more user friendly…
JPD
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29
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2 answers

What is an "XYZM" measurement model?

SpatiaLite supports a remarkable number of different dimension models. Interestingly, some of their values support a "measure" coordinate (XYM, XYZM). How would this measure-coordinate be used, and what is the correct term for searching to figure…
Brian Ballsun-Stanton
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29
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6 answers

Dealing with data that spreads across UTM Zones?

I have data that spreads across two UTM Zones GDA/MGA94 UTM Zone 55 and 56. I have layers such as a cadastre, roads, pipelines etc where I want to store measurements like lengths and areas in metres or some kind of metric notation, not…
Ando
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29
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3 answers

Cropping Shapefiles in QGIS?

I need to clip a large and very detailed shapefile in QGIS showing environmental data similar to a temperature map. Is there something like the very simple crop tool like in Adobe Photoshop where you can drag a rectangle over an area of interest…
birgit
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29
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1 answer

How do I change the polygon fill color and border color for SpatialPolygons objects?

I have SpatialPolygons or SpatialPolygonsDataFrames which I'd like to plot. How do I change the color using the three plotting systems in R (base graphics, lattice graphics, and ggplot2)? Example data: library(sp) Srs1 =…
Ari B. Friedman
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29
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6 answers

How correct is the "Accuracy" value given by GPS devices?

I have a Garmin Forerunner 305 and a Google Nexus One Android phone. From the GPS on both these devices I can get a "Accuracy" value that is usually between 6-20 meters. How much can I trust this value? Is it close to correct or may it be very…
Jonas
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29
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7 answers

How can I update ogr2ogr to include the PostgreSQL driver?

I'm trying to use ogr2ogr to upload a shapefile to a remote PostGres installation. When I ran this command: celenius:~ celenius$ ogr2ogr -f PostgreSQL PG:"host=255.34.00.00 user=postgres dbname=mydb password=***" Dropbox/data/roads.shp; I got the…
djq
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29
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3 answers

Creating new empty vector layer with PyQGIS

I have looked at a few tutorials on Python scripts for QGIS. All of them create new vector and raster layers with some existing data source e.g. shapefile or GeoTIFF or PostGIS database table. Is it possible to create a QGIS layer through a python…
Theuns Heydenrych
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29
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3 answers

Organization and tidiness of multiple copies of layers?

Back in the days when I was in the university I had a "Organization and tidiness" problem – I was unorganized and kept my layers in different folders without distinct names and hence had multiple copies of each layer. Ever since I started working,…
jonatr
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29
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8 answers

What raster-based GIS systems really work?

Raster GISes like GRASS, ArcGIS/Spatial Analyst, and Idrisi can perform a rich set of data processing and analytical procedures loosely known as "map algebra." In today's computing environment it is becoming commonplace to maintain rasters of…
whuber
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29
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3 answers

Selecting feature types when using ogr2ogr to convert to shapefile?

Shapefiles can only have one geometry type, but many other formats (kml, geojson) can have multiple types. When converting to shapefiles, is it possible to to tell ogr2ogr to create multiple shapefiles, one for each type? It seems like the "-where"…
slinkp
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29
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1 answer

SNAP vs. GDAL vs. Orfeo - image rescale, histogram cut

I work with a Sentinel-2 .jp2 image (red band, 10950 x 10950 pixels). My aim is to reach the same result what SNAP does with a Python script. See the SNAP method and parameters: So this is my reference (result with SNAP), I want to reach this…
pnz1337
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29
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3 answers

Cropping raster layer using QGIS?

How do I crop a raster layer in QGIS? I want to make contours from a section of a layer, and including the whole layer will create far more data than I need and slow down the rendering. I have found that I can do it by using the Raster calculator…
Graham vdR
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29
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1 answer

How to calculate distance to a feature with gdal_proximity?

I'm using gdal_proximity to find the distance to the nearest major river across the USA (lower 48 states). I've projected the NHD+ network flowlines to Conus Albers (epsg:5070), selected rivers with stream order > 5, and rasterized, burning rivers…
R Rhodes
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29
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4 answers

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 output raster. But, for some reason the output file is…
stn
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