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1500 questions
25
votes
5 answers
Alternatives to ogr2ogr for loading large GeoJson file(s) to PostGIS
I have a 7GB GeoJson file that I would like to load into a PostGIS database. I have tried using ogr2ogr but it fails because the file is too big for ogr2ogr to load into memory and then process.
Are there any other alternatives for loading this…
RyanKDalton
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25
votes
3 answers
Making QGIS layer update from changed data source
I'm trying to get layers to update automatically when their data source changes. I'm using R to write a shapefile with an attribute, and colouring according to that attribute in QGIS.
I want to write a new shapefile with different attribute values,…
Spacedman
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25
votes
3 answers
What projections should I use to make my own Globe?
Searching for an answer to this question, I found instructions posted by Gulf of Maine Research Institute showing how to create a globe.
Using manual methods ...
What approach would I take to create a globe using GIS?
What projection should I use…
Kirk Kuykendall
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25
votes
3 answers
Merging multiple SpatialPolygonDataFrames into 1 SPDF in R?
I have created 2 polygons in QGIS. Using them in R, polygons become automatically SpatialPolygonsDataFrame (SPDF). I would like to merge them into single SPDF (as is super easy in ArcGis using Tool Merge). I am sure that there should be simple way…
maycca
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25
votes
3 answers
What causes the GPS offset/shift in China?
I've spent close to two full days trying to understand the nature of the infamous GPS shift in China. After sifting through the noise, two recurring symptoms are that:
GPS coordinates (WGS-84) plot poorly on Chinese maps, with an offset ranging…
Dan Dascalescu
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25
votes
6 answers
Installing 3rd party python libraries for QGIS on Windows
How can I use 3rd party libraries on QGIS plugins on Windows?
I've developed a plugin that uses rasterio and numpy for a customer, but he's having problems installing rasterio and numpy.
Actually rasterio and numpy were installed in it's main…
George Silva
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25
votes
3 answers
Alternative to Google Earth to edit and organize KML files
I like the way Google Earth displays KML as a "scene graph", that is, a tree structure in the left panel.
This allows you to rearrange features in folders, change layer order, etc. via drag-and-drop.
However, this (rather useful) functionality is a…
heltonbiker
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25
votes
3 answers
How to symbolize features with NULL values in graduated symbology?
I have a polygon feature dataset, and an attribute from a different table that I join (one-to-one) within QGIS in order to symbolise the attributes as a choropleth map. However, not all polygon fields have a matching field in the table of numerical…
alphabetasoup
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25
votes
4 answers
Merge any and all adjacent polygons
I would like to do adjacency tests on a parcel (polygons) layer and merge them if they fit certain criteria (could be size). Per the picture below, I would like to merge polygons 1,2,3 and 4, but not 5.
I have two problems:
ST_TOUCHES returns TRUE…
ako
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25
votes
5 answers
How to simplify a routable network?
I have a network graph that I need to simplify in the sense of reducing the number of edges. The idea would be to merge nodes that are located close together and remove the connecting short edges.
How could this be achieved in PostGIS or GRASS? Or…
underdark
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25
votes
5 answers
Any reason to use TileMill if Mapbox Studio is meant to replace it?
I'm new to using TileMill and it still seems like a popular cross-platform package, though I keep running into common bugs and errors with it (on Mac OSX). On Mapbox's page, it says that Mapbox Studio is meant to "fully replace and improve upon…
dancow
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25
votes
2 answers
Using removeLayer of Leaflet
See the Leaflet tutorial for adding a layer control to your map:
L.Icon.Default.imagePath = "Scripts/images";
var mapUrl = 'http://{s}.tile.openstreetmap.se/hydda/full/{z}/{x}/{y}.png';
var secondMap =…
yesman
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25
votes
3 answers
How to get the centroid of a set of points in PostGIS?
I use PostgreSQL with the PostGIS extension.
I have a set of points in the_geom column from a table myschema.myobjects. I want to create a select statement to get the centroid of this cluster, so from a select statement like this:
SELECT the_geom…
Rémi B.
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25
votes
4 answers
Creating circle in PostGIS
I'm using PostGIS 1.5.2, with geometries in SRID:900913. I need create a circles using a list of points as centre, with a radius of 600 kilometers.
I'm using this query:
INSERT INTO circles (geom) (
SELECT ST_Buffer(point, 600000, 'quad_segs=8')…
angelcervera
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24
votes
3 answers
Calculating percent area of intersection in WHERE clause
I have a table of polygons (census block groups) in Postgres. I want to tag each block group with the town (another polygon table) it mainly resides within. Is this possible?
I'm thinking I'd need to essentially create something like:
select b.*,…
eirvin
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