Questions tagged [postgis]

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

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votes
1answer
2k views

Using PostGIS with Rails

I'm new to postGIS, and am looking to use a spatial database with my Rails app (specifically, to retrieve points from the database that are within the bounding box of a Google Maps viewport). I posted ...
8
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2answers
997 views

Splitting polylines using regions with PostGIS

I was wondering if it is possible to split a polyline on polygon boundaries (regions) in PostGIS, the picture below is of what we have at the moment and showing where I need the polylines split: Lets ...
8
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1answer
2k views

PostGIS 3D in Action

I was wondering if there is a website that showcases Openlayers and PostGIS 3D in Action
25
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3answers
21k views

Is there a dissolve function in PostGIS other than st_union?

I'm looking for a function to dissolve shared boundaries between polygon features in a table. ST_UNION() almost does what I'm looking for, but it creates a multipolygon from all polygons in the layer ...
4
votes
2answers
880 views

ArcSDE 10 and PostgreSQL 8.3 vs 8.4

We have recently upgraded our ArcSDE 9.3 instance to ArcSDE 10. I was hoping to upgrade postgresql 8.3 to 8.4 at the same time. Although ArcSDE 10 supports 8.4, it turns out that the ArcSDE wizards ...
19
votes
4answers
7k views

Creating one-sided buffers or parallel lines in PostGIS?

I'm looking for a way to create so-called one-sided buffers or parallel lines in PostGIS. Example: 1. buffer, 2. one-side, 3. both-sides I've found some discussion on the mailing list from 2009 and ...
22
votes
7answers
10k 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 ...
2
votes
6answers
2k views

How can I connect to a PostGIS database from ArcCatalog 9.3 via ArcSDE?

I have a problem connecting to my postgis database via ArcSDE in Arc Catalog. When i want to establish connection to my database i get an error:
8
votes
4answers
3k views

Queries returning very big datasets in PostGIS

I have a PostGIS query that will return several million rows: SELECT t1.id AS id1, t2.id AS id2, ABS(t1.mean_h - t2.mean_h) AS h_diff, ST_Distance(t1.the_geom, t2.the_geom) AS dist FROM ...
7
votes
3answers
979 views

How to get a list of adjacent lots to a road in ArcMAP and PostGIS/QGIS?

In the following map, I have: A line / road layer A parcel / lot layer The Task: Find and count the list of lots adjacent to the road with their types (parcel_type is a field in the parcel layer) ...
16
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2answers
4k views

What are the implications of invalid geometries

I've imported some data in a Postgis database and some of the geometries are reported invalid (ST_IsValidReason reports self-intersection or ring self-intersection). The queries I am performing don't ...
9
votes
3answers
4k views

How to emulate Google Maps driving directions using pgRouting?

Would like to emulate google maps' driving directions functionality but use pgRouting instead. google's data over the project area & scale is quite a bit off so we want to use our own transport ...
6
votes
4answers
5k views

Live KML from PostGIS to Google Earth

Is there a way to bring data from a postGIS database into Google Earth to view live? I know of the asKml function in PostGIS, but I'm interested to know if anyone had managed to hook up a kml so that ...
22
votes
2answers
11k views

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: ...
19
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2answers
7k views

How can I calculate the bearing between two points in PostGIS?

How can I find the bearing between two points in PostGIS? Please specify in your answer whether or not the method producing a bearing on the spheroid, or a planar bearing.
2
votes
4answers
6k views

struggling with GeoDjango install: ERROR: could not access file “$libdir/postgis-1.5”: No such file

I'm installing GeoDjango on Mac OSX. I've followed the official Mac install instructions, which all went smoothly, and am now creating a spatial database template for PostGIS. However, when I try to ...
7
votes
2answers
3k views

Unions of polygons (Postgis ST_UNION for Geography type)

I am looking for a function that will return the intersection of 2 or more polygons (geography type). I am aware of ST_UNION, ST_COLLECT but it works only for geometry type.
2
votes
1answer
1k 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 ...
3
votes
1answer
456 views

How to convert SHP/POSTGIS data into x, y, z, “cost” data?

Is there a way to convert a line layer (shp or PostGIS) data into (x, y , z, cost) i.e. (From_node, To_node, optional_Elevation, Cost/Weight) ?
4
votes
3answers
3k views

Writing a plugin for QGIS using Python to access PostGIS and write geometries

Sorry about the strange title, I didn't really know how to word it. I currently use MapInfo to do most of my GIS work however I have recently installed PostGIS 1.5 and I really like it so far. A ...
37
votes
7answers
22k views

Nearest neighbor between point layer and line layer? [closed]

I've asked this question several times on stackoverflow and irc between #qgis and #postgis and I also tried to code it or implement it my self in postgis with no real answer. Using programming (most ...
3
votes
1answer
679 views

Find polygon that contains all linestring records in PostGIS table

I'm still pretty new to this stuff, so bear with me. In PostGIS how could I find a polygon that would contain all the linestring records in a given table?
26
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4answers
6k views

Simplifying adjacent polygons using PostGIS?

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 ...
16
votes
5answers
5k views

Simplifying polygons to linestring?

I would like to simplify some polygons that represent rivers into linestrings. I assume that holes in polygons can be omitted. Anybody has some good idea how to simply do it? It would be nice, if it ...
37
votes
21answers
33k views

Connecting to PostGIS database from ArcMap for display and query without ArcSDE?

How can I connect to a PostGIS database from ArcMap using ArcGIS Desktop 9.3 and later? I would like to be able to perform spatially enabled queries and receive the results back (e.g. spatial and non-...
37
votes
4answers
12k views

Separate polygons based on intersection using PostGIS

I have a PostGIS table of polygons where some intersect with one another. This is what I'm trying to do: For a given polygon selected by id, give me all of the polygons that intersect. Basically, ...

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