huckfinn
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Does transforming to a new projection, then back, affect data accuracy?
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19 votes

I don't know which projection engine ArcGis uses, but a very interesting question also for proj.4. So I give it a try to test the proj.4 projection engine within the GNU-R environment. I use the NAD ...

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PROJ.4 How to create custom CRS to displace by x and y?
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12 votes

The EPSG:32719 is a UTM Zone 19 south setup with: $ grep -B1 '<32719>' /usr/share/proj/epsg # WGS 84 / UTM zone 19S <32719> +proj=utm +zone=19 +south +datum=WGS84 +units=m +no_defs <...

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Read a table from an ESRI file geodatabase (.gdb) using R
9 votes

I use GDAL 2.0.2 that is "shipped" with FDGB support and without a third party a FGDB driver to investigate that stuff. The test environment is Debian Jessie 64-bit. In short, it seems, that the "...

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Voronoi that don't cross boundaries
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8 votes

The buzzwords are shortest path voronoi diagram, voronoi tessellation with constraints, conforming tesselation or restricted tesselation. CGAL could help you to combine a constrained triangulation ...

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What free programs should every GIS user have installed?
7 votes

Nobody mentioned about proj.4 Proj.4 is an open source cartographic projection library and tool that works hidden in the most of desktop gis, spatial databases and gis service software (web stuff). ...

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Get individual pixel values on a raster image using gdal and python
7 votes

GDAL has all tools on board to read the data. The steps howto read data can be found in http://www.gdal.org/gdal_tutorial.html section read data. The routines GDALRasterIO or in python band.ReadRaster ...

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How to interpret a Raw AIS data sample
7 votes

There is a good github repository of Kurt Schwehr who works at the Center for Coastal and Ocean Mapping (to track whale activities for example). There you will find a decoder and documents to ...

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What format and settings to use for aerials photos in QGIS?
6 votes

For topic 2: Here is an longer investigation of JP2, because I was also interested, to use a more efficient compression. And the result IMO is: Within GDAL/QGIS (as a QgsRastrerDataProvider) you can't ...

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Creating lines to visualize differences between polygon features in PostGIS
6 votes

I think it is a little bit tricky, because of the different node sets of your both polygons (green polygon A, red different segments of polyon B). Comparing the segments of both polygons give a clue ...

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Pan sharpening of SPOT and Landsat images
6 votes

Pan sharpening is a well documented image processing technique and you will find bunch of HowTo's and tools in the web (GDAL, ArcGIS, Orfeo TB, Grass, ENVI). On a common data oriented processing ...

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What format and settings to use for aerials photos in QGIS?
5 votes

For topic 1. QGIS uses GDAL as an QgsRasterdataProvider. So the capabilities of reading and writing a raster format is implemented by the GDAL lib. You can find supported a format under the following ...

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Rasterizing polygons with the function "gdal_rasterize" in R
5 votes

I cannot recover your error but it seems that the parameters b=... l=... for band and layer are not present and I don't know what is in your data field a=class_raster, may be it is not a numeric type ...

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Lookup Projection Name from EPSG with pyproj
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5 votes

List pj_list gives you at least projections the proj command understands. The EPSG context in the proj.4 biotop is a simple file based "DATABASE" that connects ONLY EPSG number entries (KEYS) with ...

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Comparing two rasters, based on a complex set of rules
4 votes

Here is a little documented R sketch using the rgdal and raster package. # Load the raster driver kit require(rgdal) require(raster) # Set the work dir WORK_DIR <- getwd() DATA_DIR <- ...

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Where to find the WKT of a particular co-ordinate system
4 votes

If the map grid 2020 of australia is addressed Parameter Value: Longitude of initial central meridian (Zone 1) = 177 degrees west longitude Zone width = 6 degrees Central scale factor = ...

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Custom CRS not working as intended in QGIS
4 votes

The proj tool setup for the Robinsons Projection accepts only parameter for: # Longitude of projection center. # Defaults to 0.0. +lon_0=<value> # Radius of the sphere given in meters. # If ...

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How can I rename a shapefile from terminal
4 votes

Here is my little tool to "move shapes" coded in Perl. If more "sidecar files" show up, append them to the line. # Shape file extention candidates + so called side car files my @...

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Flood records/database in Europe
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4 votes

R. 70 and 80 will be difficult, Weather/ Preciptation data only: There first address for preciptation data is European Centre for Medium-Range Weather Forecasts in Reading. http://www.ecmwf.int/ ...

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Dissolve/aggregate polygons with ogr2ogr or gpc?
4 votes

If you want a pure light weight C access, you can use a combiantion of shapelib from Frank Warmerdam and gpc from Alan Murta. I find the DBF handling in the shapelib is a little bit tricky, but ...

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bathymetry (Ocean Floor depth) data - API or similar
4 votes

For Germany North Sea and Baltic Sea: Baltic sea IOW Baltic Sea Bathymetry Database Mark an area and download. North Sea AufMod sorry only german. DE: Alle morphologischen Produkte des Funktionalen ...

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Seeking comprehensive list of latitude and longitude values for cities around world?
4 votes

Use OpenStreetMap, Internet access, the wget tool and a XPath Filter like XML::XPath. The request should be chunked in 2x2 degree BBoxes. Here an example for 12 degs west till 14 degs east and 52 ...

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Seeking urban area shapefiles for France, Germany and Belgium?
4 votes

The european project Corine Land Cover gives you raster and vector data in different urban categories: 111 - Continuous urban fabric 112 - Discontinuous urban fabric 121 - Industrial or commercial ...

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How to transform WRF Spherical Earth to WGS 84?
4 votes

Proj.4 is a very flexible tool and you can define your own projection stuff, like ellipsoids / shperes via the parameter +a and +b (the semimajor radius of the ellipsoid axis). I'm not a specialist ...

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Looking for an "introduction to photogrammetry" book with a well documented chapter on UAV
4 votes

In Austria and Germany Karl Kraus taught remote sensing and photogrammetry and wrote several books which are IMO fundamental and very good for the understanding of this matter, despite the age of ...

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Are Landsat satellites exactly sun-synchronous?
3 votes

Landsat mission statement says: "Traveling on the descending (daytime) node from north to south, the satellites cross the equator on each pass at a time that provides the maximum illumination ...

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Why are there no Sentinel-2 images in northern latitudes from November to January?
3 votes

The Sentinel-2 mission uses a sun-synchronous orbit and was planned to produce image products with similar local constant viewing conditions. The planned Local Time at Descending Node per image is 10:...

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Clipping vector shapefiles more efficiently using QGIS?
3 votes

If you can use Postgresql/PostGIS I've this code snippet for you. May be this will help you. The strategy is calculate the distance between each river vertex and the station point (adjacence list) and ...

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R Raster package: write NetCDF with time dimension
3 votes

You should use the R-Package netcdf, it has much more possibilities to taylor your resulting data fields. To hold the GIS compatibility, use the Lon/Lat attribute schema beside the time attribute (...

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Relate two tables based on geom
Accepted answer
3 votes

From an example into the blue, because no routing code and not very fast O(N^2)! I have a configuration of windmills (point data) in the table windmills and surrounding objects in the table objects (...

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Importing shapefiles to a postgis on a remote server
3 votes

IMO it depends on what kind of access you have on db-server Y and the import format matters allways. Push variant You could redirect the output of shp2pgsql ... command from the maschine X to db-...

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