Topology describes non-metric relationships among geometric figures, such as adjacency, containment, and orientation. It is a branch of Mathematics, which deals in geometry without measurement.

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Generalizing polygon file while maintaining topology in QGIS?

I have a polygon Shapefile, which I need to generalize. How can I generalize the poligons and ensure that there are no topological errors like "slivers". I already tried: Vector -> Geometry Tools ...
20
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2answers
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What are the benefits of Multipart Features?

Multipart points, lines, and polygons are implemented in nearly every GIS, but what benefits, if any, do they provide? In a relational database attributes shared by different features can be stored ...
18
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1answer
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What's the status of Postgis 2.0 topology support in QGIS?

Having followed the Postgis developments over the past 6 months I have noticed a bunch of features which seem to be incredibly cool especially in the area of topologies and associating calculations on ...
15
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2answers
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How to generalize SpatialPolygons and conserving topology in R?

I would like to generalize a SpatialPolygonsDataFrame in R to make plotting more efficient. The polygons I have result in huge pdf plots that are slow to load and hard to integrate into a document. ...
14
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5answers
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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 ...
14
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1answer
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What is topojson and how is it different than geojson?

This is a conceptual question. What are the differences between these? and what are the pros and cons of these formats?
13
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1answer
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Identifying topological relationships using PostGIS

I'm trying to perform a basic typology analysis using PostGIS. My objective is to find any polygons that touch other polygons. To do this, I thought the ST_GetFaceEdges would work (reference). I want ...
12
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2answers
7k views

How to check Topology in QGIS?

I have two Shapefiles with Polygons ( City and Forerst) Is there a Plugin who is able check the topology (QGIS)? Like "Knots do not overlap" or something like that? I dont want that they overlap. ...
12
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Efficiently finding the 1st order neighbors of 200k polygons

For every one of the 208,781 Census block groups, I'd like to retrieve the FIPS IDs of all of its 1st order neighbors. I have all the TIGER boundaries downloaded and merged into a single 1GB ...
12
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4answers
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Remove Duplicate Polygons Using Open Source Tools

I have a shapefile containing features with duplicate geometries, but different attributes (e.g. a polygon with attribute XX, and an identical polygon with attribute XY). I want to identify the ...
12
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4answers
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How to connect lines in a network?

I have a shapefile of lines and another of polygons. When two or more lines intersect a polygon they should be connected (snapped), but sometimes during manual digitization this doesn't occur. I need ...
11
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7answers
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How to identify polygons with “flag” sliver errors

Working in ArcMap, I have come across errors in a polygon layer that I will call "flag slivers" (taken from similar language in parcels call "flag lots"). These sliver polygons (see image below) are ...
10
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2answers
715 views

How do I describe a special relationship between connected edges?

Consider this simple situation where three edges connect at a node: I’d like to write a succinct and clear description of the relationship between A and B in such a way that differentiates it from ...
9
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5answers
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How to convert line simple features to topological network?

using Gdal/ OGR is there a way to convert a shp, kml, or PostGIS line layer into a network of nodes and segments so it can be used in packages such as networkx?
9
votes
1answer
380 views

How to add topology to PostGIS 2.0?

I have installed PostGIS 2.0 and need new topology but it doesn't seem installed by default. I found a lot of command line to install postgis 2.0 with topology but is there a way just to add topology? ...
9
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2answers
7k views

Why Intersect gives ERROR 999999: Error executing function Invalid Topology [Too many lineseg endpoints]?

I am trying to run an Intersect process in arcgis 10 sp 3 with 2 file sets (aspect and slope) from up to a 1m DEM across an area of 65,000sq km. The aspect has 9,930,384 records and the slope has ...
9
votes
2answers
728 views

Are there Desktop GIS alternatives to ArcGIS 10.X for topology and vector conflation?

Is there any options other than ArcGIS for Desktop for topological rules and automatic topology integrity enforcing in a Desktop GIS? I am looking for something that will automatically snap features ...
9
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8answers
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How to build topology without Standard/ArcEditor or Advanced/ArcInfo license?

I have a huge dataset that I am capturing that was full of errors previously and I want to make sure that the new version is error free - which can be very time consuming with only a Basic/ArcView ...
9
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2answers
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How to preserve topology while editing polygons in OpenLayers?

I’m facing this issue: I have a chloropleth map based on a set of polygons with some data. Using WFS-T (postgis, geoserver, openlayers) I am able to edit the geometry of the polygons. This works fine. ...
9
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1answer
189 views

What PostGIS [topology] provided tools may be used for data quality assurance?

I'm learning about techniques to ensure GIS data quality. Googling around, I've found a few papers about theory and best practices (here and here), and a couple of short presentations about the topic ...
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 ...
8
votes
1answer
2k views

Splitting landcover polygons (parcels) into equal sizes, while retaining road access for all?

I would like to split landcover polygons which surround a road polygon into equal sizes, while ALL resulting polygons should have access to the road! Is there any chance to do this automatically? ...
8
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1answer
241 views

Suitable algorithms for simplifying isochrone polygons

I'm looking for an algorithm for simplifying isochrones which were generated using OSM data. These are generally characterised as having lots of small "holes" mostly due to missing OSM data but also ...
8
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2answers
720 views

How to speed up space partitioning in postgis?

I've a bunch of overlapping polygons and I'm trying to partition the space to avoid having overlapping ones. I think my problem is fairly simple. Using some ESRI product and ...
8
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0answers
221 views

Joining layers with respective elements with PostGIS Topology

I'm currently using PostGIS topology extension, but I have some difficulties in understanding how the structure works: One of the key points is the use of "layer"s: as of what I understand, features ...
7
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3answers
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Snapping start- and end nodes of lines to other lines in PostGIS

There are plenty examples that show how to snap lines to points, but I haven't been able to find any (fast!) way of snapping the start- and end nodes of line strings to nodes of other lines. ...
7
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3answers
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Create features from ArcGIS Topology errors

I have imported field users shapefiles into an ESRI geodatabase so that I can create some topology rulesets that identifies the errors as needed. Unfortunately the field users do not have a license ...
7
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2answers
936 views

What does 'building topology' mean for pgRouting?

From a couple of answers at gis.stackexchange.com and at the pgRouting mailing list I have found out that pgRouting 'builds topology'. What does that mean? If for example we import an .osm file into ...
7
votes
3answers
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Analyzing differences between two shapefiles to put results into new shapefile?

I have two polygon shapefiles of the same region from two different years (1985 and 1997) and I need to analyse the differences between the two shapefiles resulting in a third polygon shapefile ...
7
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1answer
559 views

Algorithm to fill the gaps adjacent to parcels

I would like to find a way to fill the gaps between the road and its surrounding parcels, like described in picture below: I have different parcels like A and B , i want to fill the gaps by adding ...
7
votes
2answers
4k views

I would like to know how to clean topological errors

I am a new QGIS 2.0 user. I was so impressed the new default tool, Topology Checker, in this new version. But, hundreds errors are bothering me for cleaning up features. Is it possible to clean ...
7
votes
1answer
244 views

Optimize GEOSGeometry's spatial operations by avoiding thread-safety checks

A ranking algorithm I'm developing for a Django webapp requires performing spatial operations (within, intersections, sym_difference, etc.) using a query against large number of geometry objects. ...
7
votes
1answer
411 views

How to create a topologically correct dataset in PostGIS (with GRASS)?

I have shapefiles which I have loaded in postgis and now i am trying to use geometric function in postgis like ST_intersect and they fail because the data is not topological correct. I have tried to ...
6
votes
2answers
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How to repair topology of a shapefile?

I performed an object-based image analysis using ENVI EX, and each of the classified features were exported as a shapefile. I transferred those shapefiles into ArcMap 10, and tried to intersect them ...
6
votes
4answers
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What's the difference between hypsography and topography?

I've recently come across some data that has been labeled "hypsography". I looked it up and it sounds like topography. But this data source has data labeled "topography" separate from its ...
6
votes
1answer
100 views

Dividing the world space to geographic sub-space

I am trying to divide the world space to geographic sub-space from "general" to "specific" locations and without using latitude and longitude information. That is, I am trying to think about the world ...
6
votes
1answer
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FME - Can I write back into my original file geodatabase

I have a gas pipeline network which I have stored in an File Geodatabase as polylines. I've created an FME workspace to split the pipelines at fittings (valves, reducers, tees, etc) which are stored ...
6
votes
3answers
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How to fill a hole in a multi-polygon layer on QGIS 2?

I need to fill a hole in a multi-polygon layer on QGIS 2.0. I've set the snapping option for the layer as follows : mode: to vertex and segment tolerance 4 pixels avoid intersection "enabled" ...
6
votes
1answer
97 views

Automatic creation of polygons from Feature Class points in ArcGIS for Desktop?

I have two point feature classes, let's call them A and B. They are well-spaced and the points are non-overlapping: My objective is to create a topology using these two sets of points by connecting ...
6
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1answer
331 views

Is there Open Source equivalent to ArcGIS Integrate (for topology correction)?

I need to transform a set of polygons so that it forms an exact spatial partition/tesselation (no gap - no overlap). What are the existing open-source solutions (software or library) to perform this ...
6
votes
2answers
406 views

Just view topology errors in ArcGIS

I have a basemap (parcels), which is to be used as target for several conflation tasks. This basemap MUST NOT be modified in any way. The basemap ist part of numerous topology rules. Each time ...
6
votes
2answers
112 views

Snapping leaves small gap between features in ArcGIS for Desktop?

I'm using classic snapping in ArcGIS 10.1. At the scale (1:5,000) that I'm using to snap the edge of one rectangular feature to the edge of another rectangular feature, snapping seems to work fine. ...
6
votes
2answers
205 views

What controls the direction of TopoGeometry Linestrings?

In PostGIS, what if anything controls the direction that topogeometry LINESTRINGs will have when converted to geometry? It doesn't appear to be the order in which the edges are listed in the call to ...
5
votes
1answer
834 views

3d polylines and polygons

Is there a way to extract z values from a DEM into a polyline and/or polygon featurclass in arcmap 10? I would like to have 3d polylines and polygons to make cross sections in a CAD, but currently I ...
5
votes
2answers
314 views

Determining if landlocked polygons in ArcGIS Desktop?

Imagine that I have the need to determine landlocked countries. Is there a way to do it automatically? Any known implementations? The target platform on this will be ArcGIS.
5
votes
4answers
764 views

How can I create polygons of the area surrounded by roads / lines?

I'm currently trying to create polygons that represent the areas surrounded by roads. The roads are stored in PostGIS as points / lines so I have flexibility over what I can do with them. I'm ...
5
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3answers
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How tool to split polylines into two-part lines at vertices in ArcGIS for Desktop 10.1?

I'm using ArcGIS 10.1 SP1 at and we have a problem. There is a serious topology bug that I've mentioned in another question that is affecting our workflow. At present, Esri has stated the fix will be ...
5
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1answer
398 views

How do I save topology errors in QGIS?

I'm currently doing a project on finding blocked roads in a road network layer. I've figured that I can use the topology checker with the rule 'must not have dangles' and find them this way. But I ...
5
votes
1answer
690 views

Road Topology Problem solution for junction

I am working with a Road Network. I have digitized the lines with AutoCAD Map 3D. Then Imported it to ArcMap. After entering all kind of database I have created Routing Dataset. But unfortunately its ...
5
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1answer
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How you can repair invalid topology errors within postgis?

I've imported the shapefile of corine land cover project to my postgis database and the select gid, ST_IsValidReason(geom) from gis.clc2000 where not ST_IsValid(geom); returns in every occasion ...