PostGIS is an extension for the PostgreSQL object-relational database that adds support for geographic objects.

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17
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Simplifying adjacent polygons

I encountered a problem simplifying set of polygons that are adjacent. If I simplify each polygon separately with the Douglas–Peucker algorithm (which is used by many open source tools), the resulting ...
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6answers
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Spatial databases learning resources for newbies

Would be taking up a course on spatial databases next semester. Would anybody know a newbie friendly introductory resource? A vendor neutral one would be preferable. Thanks.
18
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2answers
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How to change the geometry type from Point to Multipoint within an existing table in PostGIS?

Is there a PostGIS function that can change geometry type for an existing table? We need to change from POINT to MULTIPOINT. The table will be empty when we change the geometry type and we cannot ...
12
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1answer
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Open-source GIS implementation of the Huff model

This might be a stretch, but I was wondering if anyone implemented gravity modeling tools or scripts for Retail Market Analysis (like the Huff Model), to analyze spatial data for customer-store ...
26
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4answers
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What is the best way to join lots of small polygons to form a larger polygon?

I have the following layer using SRID 27700 in postgis: It's every administrative region in the UK, and (as you can see from the colour grouping) each of them has a text field specifying the county ...
18
votes
7answers
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How to migrate data from ArcSDE to PostGIS?

Its been suggested that i ask this question again, but perhaps worded differently than how to Bulk load multiple shapefiles into PostGIS. I'm new to postgis and sql but i want to use postgis as a ...
13
votes
2answers
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How to calculate the angle at which two lines intersect in PostGIS?

I want to calculate the angle between two lines where they intersect in PostGIS. The starting point for angle calculations in PostGIS seems to be ST_Azimuth - but that takes points as input. My first ...
28
votes
4answers
24k views

Why does PostGIS installation not create a template_postgis

I went this route for installation of PostgreSQL and PostGIS: PostgreSQL using the standalone KyngChaos, PostGIS install from KyngChaos as well... pgAdmin3 from PostgreSQL Tools Now when I launch ...
12
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3answers
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Optimizing a nearest neighbor calculation using PostGIS

I'm using PostGIS to calculate the nearest neighbors of polygons. What I want to calculate is the minimum distance from each polygon, to the nearest polygon. Thus far I have got great help from Mike ...
9
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1answer
2k views

One to Many Relationship in QGIS with PostGIS

Does anyone know of any tool that can do a One-to-Many relationship in QGIS. I have my data in a PostGIS database. I would like to be able to query spatial layers that are related to spatial or non ...
13
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6answers
16k views

How can I enable Shapefile GUI Loader in pgadmin3?

I have installed PostgreSQL 9.1 with PostGIS 1.5.3 on Ubuntu 11.10. I also installed pgadmin3 1.14.0-beta1, following this instructions. If I remember correctly, when I installed PostGIS on Windows ...
32
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2answers
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What coordinate system should be used to store geography data for celestial coordinates?

I am doing an astronomy project. I want to have the information about our images stored in a spatially enabled database. This, I would think, should be a very easy special case for GIS functions ...
25
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3answers
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Meaning of Simplify's tolerance parameter

The standard parameters of Douglas-Peucker's simplify algorithm are geometry and tolerance (e.g ST_Simplify in PostGIS). What's the meaning of the tolerance parameter? I know that the bigger the ...
18
votes
5answers
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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. ...
10
votes
2answers
12k views

Adding shapefiles to PostGIS database

I was able to create a Postgresql database and then I executed, createlang plpgsql geospecies psql -d geospecies -f postgis.sql psql -d geospecies -f spatial_ref_sys.sql So now can I directly ...
6
votes
1answer
717 views

calculate slope for a road network

I am working on a road network for routing operations using postgis and QGIS. I am new to both of these tools and need to calculate the slope for each edge (by retrieving the Z value for the start ...
6
votes
1answer
650 views

Filling a polygon with lines using Postgis

i need to calculate a specific distance in an area. The distance is calculated from parallel lines in a polygon, And i need to find out how many parallel lines (with x meters distance to each other) ...
12
votes
2answers
585 views

What is the best hack for importing large datasets into PostGIS?

I have to import large Shapefiles (> 1 million records) into PostGIS, and I have been wondering about the best way to do it. In my question I used the word "hack", instead of tool, on purpose ...
12
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5answers
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Large shapefile to raster

I have a large shapefile (1 gb) and need to rasterise it. I have tried the following already. 1.) Import it into GRASS using v.in.ogr this failed with the error message: ERROR: G_realloc: unable to ...
8
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1answer
6k views

How to create a table from existing tables (applying new schemas) in postgis DB?

I have a table that is geospatially enabled; that contain world borders. I want to break it down to different schemas (global, europe etc..) . My thought is to use use something that looks like this: ...
7
votes
1answer
2k views

What is a “non-noded intersection”?

Can someone provide a precise definition of what a "non-noded intersection" is? There are various GIS platforms and toolkits that have errors with this text, and Google search results for this tend to ...
6
votes
3answers
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Point in polygon algorithm for multiple polygons

I've a Google map with bunch of polygons on it. Here is a problem I'm interested in: Given a lat,lng point, what's the best way to determine all the polygons that this point lies in? The obvious way ...
5
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2answers
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Using OpenLayers (with OpenStreetMaps) and PostGis for rendering data acquired from GPS tracking device?

I'm researching and planing to acquire data from GPS device and store them in postGIS database, then use geodjango to process/work them out and finally chart them on a map with OpenLayers. Will these ...
8
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2answers
670 views

PostGIS Union Between Two Tables, Preserving Attributes

I'm trying to union US State level upper- and lower-level government boundaries in such a way that generates one PostGIS table with both the upper and lower level names for each shape. In my example ...
8
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3answers
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Retrieve polygon smallest MBR

I have a postgis table containing polygons. I want to transform my polygons to 4 points polygons : retrieve the smallest MBR. Here comes an illustration of what I want : My original polygon is ...
7
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3answers
580 views

Is there a paid service for accessing a PostGIS/OSM DB

I want to render a world map with mapnik and postgis, but do not want to set up my own DB, because the needed hardware and processing time for the OSM import make it nearly impossible for me. I just ...
6
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2answers
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Storing GPS tracks with timestamps in PostGIS

I need to store a series of GPS points with timestamps in the database (traces of various vehicles). I am wondering which of two approaches to choose for storing them in the PostGIS table: 1.) Each ...
5
votes
2answers
517 views

Symbolising null features 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 ...
5
votes
2answers
589 views

How to add sfcgal to an already postgis enabled database

I have a postgres 9.1 database with postgis 2.1, and I recently needed to add sfcgal to it, so i rebuilt postgis 2.1, but I can't find out how to update the postgis extension in postgres without ...
5
votes
2answers
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Count Points in Polygon with Postgis

I've got a simple problem: I want to count the number of points within a set of polygons. I have a SQL already but it only gives back the gid of the polygone that actually contains points. My ...
4
votes
4answers
1k views

GeoServer Layer from PostGIS not updating

I created a WMS layer from a PostGIS table with a fraction of total polygons in GeoServer. Everything displayed fine. Then, I added the rest of the polygons to the table in postgis. For some reason ...
2
votes
3answers
3k views

Render vectors from OSM data in POSTGIS database

I'm a newbie when it comes to mapping application. I had successfully loaded my OpenstreetMap data in a Postgresql/PostGIS database. Now my problem is how to render the vector data (the POI's, ways, ...
7
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0answers
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Loading raster from PostGIS DB into QGIS: succeeded yesterday, fails now [closed]

I have a PostgreSQL(v.9.2)/Postgis(v.2.0.3) database which includes raster layers (added through raster2pgsql). To open them in QGIS (v.1.8.0-Lisboa), the "Add Postgis layer" menu will not work; ...
7
votes
4answers
611 views

Is there a way to identify and remove similar GPS tracks in PostGIS or ArcGIS?

I have a large number of GPS tracks from a number of different users. I'd like to identify tracks that take the same route and remove those duplicates. For example, a user takes the same streets from ...
6
votes
3answers
4k views

PostGIS non functional on Ubuntu 14.04

I am unable to create the PostGIS extension on new databases in Ubuntu 14.04: $ psql pg_testing -c "create extension postgis" ERROR: could not load library ...
5
votes
2answers
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How to group connected linestrings in PostGIS?

I have a table of streets I've selected based on a set of attributes (let's say it's speed_limit < 25). There are groups of streets that are locally contiguous; I'd like to group these sets of ...
5
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3answers
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Loading raster data to postgis

I'm a newbie in GIS technology and need some help in loading a rainfall radar raster data into PostGIS. The raster image is shown here: What I need is to store in the database the radar ...
4
votes
1answer
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How to create linestrings with a definite angle and length, that are fixed to a point

I want to create linestrings with a definite angle (e.g. 160°) and length (e.g. 2m) that are fixed to a number of points of another linestring. So, I want to use the ST_DumpPoints function to find the ...
4
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3answers
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How to speed up Postgis raster layer display in QGIS?

i've been importing some digital orthophoto geotif files into postgis 2.0.1 via raster2pgsql tool (i also made 3 levels of an overview table - pyramid). Then i tried to import the layer into qgis via ...
4
votes
3answers
2k views

Newbie PostGIS Geometry and Multilinestring Clarification

I'm having some trouble figuring out if I've got the right data loaded for PgRouting. Using the bash script included in PostGIS 2.0, I loaded Tiger2010 data for U.S. State California. The edges ...
3
votes
1answer
281 views

nearest facility with pgrouting

I have a postgres table of students with lat, lon and geom, , and a table of schools with the same, and a table of roads that has been converted to nodes. I'm trying to find the driving distance to ...
3
votes
1answer
595 views

PostGIS Raster in MapServer

I'm having trouble getting a PostGIS raster to load and display in MapServer. I'm not sure, but suspect it's a version problem. My mapfile layer and the error message are shown below. LAYER ...
3
votes
1answer
160 views

Nearest neighbour for every row

I'm relatively new to PostGIS and postgresql . I'm trying to build a simple query containing two relations as follows : I've two relations R1 and R2 both of which contains geometries(Points) . I ...
3
votes
1answer
9k views

Transforming from SRID 900913 to 4326 with PostGis

I have two Postgres tables with different SRIDs: 4326 and 900913. I want to convert the latter to 4326. I first changed the SRID using: Select UpdateGeometrySRID('table', 'geomcolumn', 4326). I ...
3
votes
3answers
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How to Calculate length of polyline geometry for several tables in PostGIS?

PostGIS database contains several geometry (polyline) tables (with names "D1_r", "D2_r", "D3_r"). I calculate length for one "postgis layer" use request: SELECT ...
2
votes
1answer
1k views

Extract lat, lon Points from Polygon

I have PostGIS database, and want to extract lat, lon pairs sequence from Polygons (and MultiPolygons). As a very fresh PostGIS user, I'm able to just extract the Polygons: SELECT ...
2
votes
1answer
385 views

How to split polygons with another polygon and inheritage data?

Let's say that we have two tables with polygons representing areas. Table A and Table B. Geometries from table A represents both the valid and invalid areas. And the geometries in table B represents ...
2
votes
2answers
3k views

What Spatial Reference System do I store Google Map's Lat/Lng in

I am new to PostGIS, Spatial Reference Systems and projections and want to store lat/lng coordinates retrieved from Google Maps and Openstreetmap and its services like the Geocoder/Nominatim. I'm ...
2
votes
1answer
316 views

Hyperlinking to PostGIS Layers and Zip files with QGIS Actions

I previously asked a question about hyperlinking data in QGIS that gets loaded into QGIS (see post: Hyperlinking in QGIS - Add Data to current window). A user provided me with the code, which works ...
1
vote
1answer
547 views

overlay my shapefiles stored in database to the web/browser [duplicate]

I am very much strrugling on how to display my shapefiles stored in postgis database to the browser or to the web.. is there anyone there knows how to do it.? I am using geodjango framework in ...