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

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How can I find a point inside a polygon in PostGIS?

How can I find a point that is guaranteed to be within a given polygon in PostGIS? I am aware of the ST_Centroid function. However, the centroid is not always within a polygon, see below: ...
12
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1answer
2k views

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 ...
28
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4answers
26k 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 ...
14
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2answers
3k views

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 ...
12
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3answers
3k views

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 ...
10
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2answers
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How do you display related records in QGIS?

Coming from an esri background I have always used relationship classes in a gdb to display records related to a feature. Eg. Relate 1 survey point to many documents, photos etc. Does any one know how ...
9
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1answer
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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 ...
18
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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. ...
15
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7answers
18k 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 ...
31
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3answers
5k views

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 value,...
14
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3answers
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Identifying road intersections using PostGIS

I'm trying to identify where roads intersect each other, and to make a point at this intersection, with the number of roads that form the intersection listed. I was wondering if there was some way ...
8
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1answer
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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: ...
6
votes
1answer
682 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) ...
6
votes
1answer
808 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 ...
3
votes
2answers
839 views

Finding points along a path

I am unsure of the best approach to this problem. I can think of some ways of doing it which I will list below but I am looking for the best and most efficient way of doing this. Problem Given a ...
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 ...
7
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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 ...
7
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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 ...
10
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5answers
621 views

Database versus Files for Solo Developer

I'm just getting started in GIS and am interested in using it to create maps of mountain biking trails in my area and nearby. I've been learning QGIS and have made enough progress to generate a decent ...
10
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1answer
1k views

How to render a table with mixed geometry types in QGIS?

I created a table with geometry type "GEOMETRY" AND inserted data of point, line and polygon type. My question is how to show this spatial data Qgis not supporting for geometry type "GEOMETRY".
8
votes
2answers
752 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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2answers
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Difference between two layers in PostGIS

What is the right way to calculate the difference between two layers? I tried to use the following approach: SELECT ST_Difference(river.geom, lakes.geom) FROM river LEFT JOIN lakes ON ST_Intersects(...
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 "/usr/lib/postgresql/9.3/lib/postgis-2.1....
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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
733 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 ...
4
votes
4answers
4k views

Calculate distance of point from an arc/polyline

Using Postgres/PostGIS, I am trying to query the database for the closest arc to a particular GPS point. Each Arc is made up of two nodes that are GPS points on a map. Is there a way I could query ...
4
votes
4answers
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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 ...
3
votes
3answers
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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 ...
3
votes
3answers
4k views

Connnect to PostGIS db using QGIS - when not on localhost

I"m just getting started with PostgreSQL/PostGIS db (v9.2) and I'm wanting to connect to db while not on the localhost using QGIS. I've been able to connect successfully on localhost, however I'm not ...
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, ...
8
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2answers
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PostGIS Geometry Query returns “Error: Operation on mixed SRID geometries” only for certain values

I have PostGIS table with two geometry columns, both defined with SRID 4326. I can insert into the table without problem, using the following INSERT statement (where lng and lat are values passed in ...
8
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1answer
3k views

Ring Self-Intersections in PostGIS

This is a follow on from previous question. You will see I am a new PostGIS user. I have looked at the validity of the topology in my data and find around 1700 topology issues in the landcover (...
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
705 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 ...
7
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4answers
5k views

How to extract POINT from a [LINE|MULTILINE]STRING

I'd like to create a vectorLayer in QGIS to display all the points that form a LINESTRING or a MULTILINESTRING stored in a PostGIS DB. I think that I need to transform all points of LINESTRING (or ...
7
votes
2answers
3k views

SQL query to have a complete geojson feature from PostGIS

I would like to get a geojson feature with properties from PostGIS. I have found an example to have a feature collection but I can't make it works for just a feature. so far I tryed to modify the ...
6
votes
3answers
4k views

PostGIS: parse geometry wkb with OGR

I'm trying to pull a LineString geometry out of PostGIS and parse it with OGR (python bindinds). from osgeo import ogr import psycopg2 connection = psycopg2.connect("...") cursor = connection.cursor(...
5
votes
2answers
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How to add Geoserver WFS to Leaflet JS Application

I have a PostGIS database and have successfully consumed a table into GeoServer and published a WFS. Are there REST endpoints available for these WFS' akin to ESRI's feature services? How are ...
5
votes
3answers
6k views

What's the fastest way to do a bounding box query in PostGIS

I have a Postgres table, with almost 2 million rows, with a long-lat coordinates field in the form POINT(-73.4938 33.2405). Supposing there's a geospatial index on that field, what's the most ...
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
1k views

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
votes
3answers
1k views

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
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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 ...
4
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1answer
11k 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
2answers
1k views

How to export thousands of features from PostGIS to a single GeoJSON file?

I know how to export one feature from a PostGIS database using ogr2ogr: $ogr2ogr -f GeoJSON out.json "PG:host=localhost dbname=xxx user=xxx password=xxx" -sql 'select id, county, wkb_geometry from ...
3
votes
3answers
2k views

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 sum(ST_Length_Spheroid(the_geom,'...
3
votes
1answer
184 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
357 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 ...