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1500 questions
25
votes
1 answer
Nearest Neighbor problem in Postgis 2.0 using GIST Index (<-> function)
I'm trying to use PostGIS 2.0 new function <-> (Geometry Distance Centroid) in order to calculate, for each row of my table (cosn1), the distance to the nearest polygon of the same class.
I was trying to use the following code:
WITH index_query AS…
Alexandre Neto
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25
votes
1 answer
Simplify polygons of sf object
How do I simplify an sf polygon without introducing gaps and slivers?
With a shapefile, for example, I would use…
Phil
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25
votes
1 answer
How to get size of file geodatabase feature class on disk?
Is there a simple way to determine the amount of hard drive space a feature class takes up?
I feel like I'm missing something simple, but I don't recall a method that does so.
You would think that right-clicking a dataset in ArcCatalog would do it…
Tanner
- 7,375
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- 109
25
votes
1 answer
Understanding QGIS buffer tool units
I have had no luck getting the buffer tool to accept anything but degrees as units of measure.
I have found lots of stuff saying the layer needs to be reprojected and saved but it hasn't worked at all for me.
Is there a way I could create a buffer…
haxwithaxe
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25
votes
7 answers
Spatial reference for dummies?
Can anyone recommend a good reference or tutorial that explains the principles of spatial references, projections, and coordinate systems?
We are a small team of programmers working with GIS technology, and we often get snagged when working with…
nw1
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25
votes
9 answers
How can I implement ESRI REST API?
ESRI announced that they are releasing the ArcGIS REST API as open technology. I've got an ISP running Sql Server 2008 with IIS7.
Does anyone know of a good walk through showing how I can write C# using WCF to expose spatial tables compliant with…
Kirk Kuykendall
- 25,787
- 8
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- 153
25
votes
15 answers
How do you explain what GIS is?
Whenever I do a presentation about anything related to GIS, I consider the level of knowledge of GIS of the audience. The worst times are definitely when I need to explain GIS to a group that has almost no knowledge about it. I said virtually,…
Ragi Yaser Burhum
- 15,339
- 2
- 59
- 76
25
votes
1 answer
How to tell which QGIS plugins are slow to load?
We have new users of QGIS in our office that are dismayed immediately by the startup time of QGIS - which hangs on the 'Restoring Loaded Plugins' message on the splash screen.
Is there a way to tell which plugins take long to load and are causing…
DPSSpatial_BoycottingGISSE
- 18,790
- 4
- 66
- 110
25
votes
6 answers
Converting polyline to polygon in QGIS
I have a shapefile with city areas, but unfortunately the shapefile only contains single lines. The shapefile looks like this:
I want to convert those lines to an area-polygon shapefile in QGIS. I tried it with the "Lines to polygons" tool (Vector…
Mark White
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25
votes
2 answers
Seeking Algorithm to detect circling and beginning and end of circle?
I've got lots of flight data from glider pilots in the form of gps fixes in a fixed interval.
I would like to analyze the flight path and detect the start and the end of the 'circling' the glider pilot will do when he finds thermals.
Ideally, an…
pgross
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- 3
- 12
25
votes
3 answers
How are GeoTIFF pyramids/overviews standardised?
While pyramids/overviews are not part of the GeoTIFF standard, many tools support creating them. For example vips/nip2, Orfeo Toolbox (otb) and ossim which all promise some support for creating those. But I have no idea if they would all create…
bugmenot123
- 11,011
- 3
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- 69
25
votes
3 answers
Assigning row number for sorted table by column in QGIS
In QGIS 3 the Field calculator has a great function called @row_number (in QGIS 2 it was $rownum) which returns (assigns) the number of the current row.
Is there a way to make it work together with sorting?
Let's say I want to sort table by column…
Miro
- 9,744
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25
votes
9 answers
Merging lines with slightly different endpoints in QGIS
In QGIS, I have two lines. The endpoints are near each other, but not quite aligned. I'd like to turn the two lines into one, with the two endpoints merged into midpoints.
The closest I've been able to come is with "Merge selected features." That…
Evan
- 1,103
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25
votes
1 answer
How to make band composite image in QGIS
I am wondering how I can make a band composite from three large bands files from Landsat? I was using option Raster>Miscellaneous>Merge but when I try to do it it crashes.
Dragan
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- 8
25
votes
7 answers
Filling holes in polygons using QGIS
Is there an option in QGIS to fill holes in polygons automatically by setting parameters e.g. maximum area, distance between borderlines?
I want to delete/fill holes that a very "thin"/small.
J-Man
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