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

learn more… | top users | synonyms

3
votes
2answers
5k views

How to find nearest line from point using PostGIS?

I have a table of Roads in PostGIS which geometry is "geometry(MultiLineString,4326)". Its attribute are gid osm_id name ref type oneway bridge maxspeed geom Now i want to know ...
2
votes
1answer
919 views

Get a single cluster from cloud of points with specified maximum diameter in postgis

I have on the order of 2M Geometry Collections with N (median: 2, stddev: 6.6, 75th: 6, 95th: 21) Point objects (repeated points allowed and important) in a PostGIS table. I want to identify clusters ...
8
votes
2answers
2k views

Performance of Shapefile and PostGIS with GeoServer?

I'm going to build a web application, which will render around ten maps using GeoServer. I will be also changing the attribute data in the application for some layers. What is the recommended choice ...
4
votes
2answers
2k views

Postgis, get the points that are x meters near another point, in meters

I'm trying to find the points within a certain distance, in meters, from another point. I'm using the function ST_Buffer, but I don't get how to express the distance in meters. I'm trying with ...
1
vote
1answer
82 views

Transform to SRID 900913

How i can transform the geometry WKB for example: ...
1
vote
1answer
1k views

How to verify a PostGIS installation on OS X?

I am trying to set up GeoDjango and installing PostGIS on my mac and when I am trying to ./configure I am getting this error checking PostgreSQL version... PostgreSQL 8.4.9 checking libpq-fe.h ...
50
votes
8answers
10k views

How to create Vector Polygons at the same amazing speeds GISCloud is able to render them?

EDIT (outlining new bounty added): I have added the largest bounty possible to this question in hope of getting a very detailed answer. Your solution should outline a step-by-step guide utilizing open ...
22
votes
4answers
12k views

How to get the nearest point on a linestring to a given point?

I've been using PostGIS for a long time now but never had to use the LINESTRING geometry ...! :) Here's what I would like to do : I have a table of linestrings (representing streets of a given city, ...
30
votes
6answers
15k views

Migrating geodatabase data into PostGIS without Esri apps?

Can you tell me how I can load geodatabase data into PostGIS without having to install Esri apps? The solution I found online talked about using ArcGIS to convert GDB to SHP and then importing SHP ...
20
votes
4answers
4k views

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 ...
27
votes
2answers
9k views

Looking for fastest solution for Point in Polygon analysis of 200 million points

Apologies for asking a question that has been asked before -- I've read through answers, and I'm left wondering how to implement the recommendations. I've never used SQL, Python, C, and have only ...
20
votes
7answers
9k views

Options for displaying PostGIS vectors in OpenLayers

I am very new to web-mapping, so this question may be a little misguided. I want to have a very simple web interface using OpenLayers (or even Google Maps if that will be easier) which can display a ...
14
votes
5answers
2k views

Find pseudo nodes in free GIS software

Software gvSIG OA Digital Edition 2010 have tools topology for finding pseudo nodes in linear geometry. I set cluster tolerance 0.00002 and maximum number of errors -10000 for 20000 link count linear ...
22
votes
2answers
14k views

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 ...
28
votes
4answers
16k views

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
2answers
7k views

In PostGIS is it possible to create a View with a unique ID?

When I create a view in PostGIS is there any way to add a unique ID to that view? Just like the "gid" field in any other PostGIS table? Edit: Sorry I should have included this in the original post. I ...
16
votes
2answers
3k views

How can I merge/collapse nearby and parallel road lines (eg. a dual-carriageway) into one single line?

I have a shapefile from OSM which contains all the roads within a city. Larger roads (like dual-carriageways) seem to have 2 parallel lines. I'd like to collapse / combine those into 1 line so I can ...
18
votes
4answers
7k views

How to create a 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) ( ...
15
votes
2answers
17k 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 ...
15
votes
1answer
1k views

Can PostGIS and QGIS provide dependable multi-user editing?

After considering a few options, I'm trying to give my 15-20 QGIS 2.2 users the ability to concurrently view/edit one or two basic point PostGIS layers, largest one has just 16,000 records. I've ...
12
votes
5answers
471 views

What in-depth spatial database systems tutorials exist?

Is there a good tutorial that explains in depth the internals of a GIS and a spatial database system such as PostGIS with examples and without any background assumption? I'm specifically looking for ...
3
votes
1answer
3k views

How to find the nearest point projected on the road network?

I would like to know if there is a function at pgRouting that given a point (lon/lat) can give you the projection of that point to the road network . Thanks in advance john
14
votes
2answers
717 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 ...
7
votes
2answers
2k views

How to get multiple shortest paths with PgRouting in one query?

I want to run shortest path algorithm on multiple source&target pairs at once and get a result as a table and process it then. How do I do this? This query does not work: SELECT a.source, a....
5
votes
2answers
1k views

How to perform SIA or Bezier line smoothing in PostGIS?

Can anyone provide an example SQL for smoothing linestrings from postgis table using Bezier curves or Iterative Averaging (SIA) algorithm?
7
votes
1answer
6k views

How to import a raster into PostGIS?

I'm trying to follow the instructions here to load a raster into a PostGIS database: python raster2pgsql.py -s 4269 -I -r *.tif -F myschema.demelevation -o elev.sql I understand that I replace * ...
7
votes
3answers
2k views

How to create spider diagrams (hub lines) in PostGIS?

I'm rather new to PostGIS but I have done a lot of reading. One thing that I have been searching for is a function that allows users to create a "spider diagram" (also called "desire lines" or "hub ...
6
votes
2answers
5k views

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 tables:...
11
votes
3answers
2k views

How to interpolate GPS Positions in PostGIS

I have a PostGIS table of GPS positions for every five seconds: 2011-01-01 00:00:05, POINT(x1,y1) 2011-01-01 00:00:10, POINT(x2,y2) 2011-01-01 00:00:15, POINT(x3,y3) ... I'm looking for a query ...
11
votes
1answer
4k views

Merge Multiple Tables into a New Table in PostGIS

I am looking to merge a number of individual tables into a new table in PostGIS. This is an easy task when working with Shapefile data, but I am unsure how to do this in PostGIS. Any help would be ...
11
votes
2answers
7k views

Finding the closest Geometry in PostGIS

I've been looking over the PostGIS "API" of functions, and I notice that most of them take two elements to compare. For example, the ST_Distance function takes two geometry/geography elements to find ...
10
votes
2answers
901 views

postgis, extrapolate a line

I'm trying to extrapolate from a line segment to find a point on the line but a 3rd of the way 'back', i.e. trying to find point new, given points A and B below: Given a line, I can interpolate it ...
5
votes
2answers
475 views

How to connect points (bus stops), which don't lie on the lines (LINESTRING), to a network?

I need to connect bus stops (points) to a network layer (OSM data). These bus stops do not lie directly on the lines (see screenshot) nor should their location be moved. I use PostGIS, pgrouting and ...
5
votes
2answers
1k views

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 ...
4
votes
2answers
2k views

I want to edit corresponding postgresql data of a vector from openlayers- how to do it?

I want to edit the corresponding text/numeric data type columns of a vector through openlayres, when a user click/mouse over a vector. like, http://dev4.mapgears.com/bdga/bdgaWFS-T.html# any ...
3
votes
2answers
6k views

How to install PostgreSQL 9.2 with PostGIS 2.0 on Ubuntu 11.10 (or higher)?

I have read this question: Install PostGIS v2 for PostgreSQL v9.2, but it didn't resolve my problem. I added the PostgreSQL backports PPA and installed the postgresql-9.2 package, but there is no ...
4
votes
2answers
2k views

What is this PostGIS query doing to show great circle connections?

I'm trying to draw a flight map in CartoDB. My starting point is a single lat long point. We'll pretend it is this: ST_GeomFromText('POINT(-71.060316 48.432044)', 4326) And I want draw lines ...
1
vote
1answer
865 views

psycopg2 error with QGIS 1.5

So I just installed QGIS 1.5 using the windows installer not the osgeo4w one and now any plugins that need access to PostgreSQL databases don't seem to work, they all throw a: "Couldn't import Python ...
9
votes
1answer
3k views

How to perform a spatial join of point and polygon layers in PostGIS?

I have a point dataset representing households that I want to associate with a parcel layer (i.e. assign its parcel_id). With ArcMap, I could spatially join the polygons to the points and specify that ...
8
votes
2answers
526 views

Clarification of the “25D” option in ogr2ogr

[EDIT: In my original post, I had received an error that was based on a typo, so I scrapped that part of the question, but left the questions that still apply.] In the ogr2ogr docs it says: -nlt ...
7
votes
1answer
1k views

How is ST_PointOnSurface calculated?

The PostGIS documentation states that ST_PointOnSurface returns "a POINT guaranteed to lie on the surface". It seems like this function could be trivially implemented to give results that satisfy the ...
5
votes
1answer
3k views

Install PostGIS on Ubuntu 12.04

I am trying to install PostGIS on Ubuntu 12.04 and I think everything is installed correctly except for postgresql. I followed this post. I get the following error and nothing I do seems to satisfy ...
5
votes
1answer
4k views

How to Import ESRI Geodatabase format .gdb into PostGIS

I ran into a problem when loading a ESRI Geodatabase format .gdb into PostGIS. I have data 2.5GB GDB file. I followed some tutorials on the internet, but it seems that doesn't work out. I created a ...
4
votes
2answers
5k views

How do I use st_dwithin with meters?

I am trying to follow PostGIS ST_Buffer Radius Help to use a 50 meter distance but postgis is returning an error. I am trying the following SQL, SELECT id FROM table WHERE ST_DWithin(...
3
votes
2answers
279 views

How to remove spikes in Polygons with PostGIS

I'm trying to validate the topology of a shapefile. I managed to repair cases of overlap and gaps, but i can't resolve cases of spikes. The image shows one example of this situation. I used the ...
3
votes
2answers
1k views

QGIS DB manager Import layer/file tool won't allow me to choose “Append data to table”

I want to append some data to a layer in my PostGIS DB using a shapefile, but when I use the Import layer/file tool in QGIS, it doesn't allow me to choose the append option. Why is this and how do I ...
1
vote
1answer
310 views

pgrouting unexpected output

Thats my ways.shp file. I loaded this to PostgreSQL DB using PostGIS shape file loader. I ran pgr_anlayzeGraph() on it and found it had a lot of isolated segments. Next I ran pgr_nodeNetwork() to ...
1
vote
2answers
1k views

ST_DWithin uses Geometry or Geography type

assuming I use the following query to match the locations to a poi within 10km distance: SELECT poi.poi_id, h.loc_id, (ST_Distance(poi.geom,h.geom)*111.111) as distanceinkm FROM iut_poi_transl AS poi,...
36
votes
3answers
20k views

Best GIS system for high performance web application - PostGIS vs MongoDB

I am working on a web/mobile application based on location data. Since i am already familiar with MongoDB, i found the geospatial indexing of mongo is quite suitable for my needs. As i am mainly ...
18
votes
7answers
3k views

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 ...