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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How to set the tolerance value in pgr_createTopolgy function of pgrouting?

I am making a map based on the floor plan of a building. I made the shapefile and added it to the postgresql database. I created the topology for the map using the following code: SELECT ...
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60 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 ...
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25 views

In ArcGIS 10 - how do I clip an arc

I have an arc that has violated the topology rule that the road feature should not extent outside of my boundary. I tried to use the clip tool in editor but cannot complete the clip. I should be able ...
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64 views

Where can I find topology-related algorithms used in QGIS?

I have shapefile with polygons and I test topology - overlaps, duplicates and gaps. I tested it in QGIS and now I have to describe algorithms, which uses QGIS for this rules. I must write research ...
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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 ...
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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 ...
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107 views

Joining layers with respective elements with PostGIS Topology

Recently I have started 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, ...
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Topology validate error

Im using Arcmap 10.1 version.I don't know where i made mistake my database. I have attached an example image to show the Error Report.
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Is there a way to build topology and work with topology relations in PyQGIS?

Is there a way to build topology and work with topology relations in PyQGIS? I'm asking because I need to run some custom generalization algorithms on my data, and I need to preserve topology. ...
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Is the TIN created out of several cross sections different from merging the TINs created out of each set of two cross sections?

I have a river with cross sections that have the water surface elevation values. I am trying to create TIN from the water surface values and then compare it with the topo (to see the flooded areas). I ...
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GeoDatabase topology and rules with a *.rul file

I have been working for some time on a solution to a problem much like this question. I have several layers that I want to resolve together. I have them all in topology (geodatabase) and have been ...
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Snapping line endpoints to a point feature class by adding a vertex

I have a line feature class whose endpoints should snap to the closest point in a points feature class. The problem is, I do not want the lines to move, but rather a vertex must be added to the ...
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Batch Clip (Editing Session)

I'm trying to correct some topology errors in my geodatabase, now focusing on two feature classes: grass and buildings. They must not overlap. However, there are plenty of spaces where the grass was ...
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How to simplify a self intersected / self overlapped polyline using ArcObjects?

I have a self intersected polyline, how can I break it into 5 records stored in the same table using arcobjects? (splited by vertices and the intersection point) Here is what I have got and it ...
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How can I edit spatial data automatically on postgis and check for topology errors on said data whitout using shapefiles?

So, I have spatial data stored in postgis (points, lines and polygons) and would like to edit and update those in an Open Source software (quantum GIS, grass, etc.) to check for topologic errors, ...
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Vertex and Nodes Tool - Migrating from 9.3.1 to 10.2.1

A previous employee built a custom tool for users in our organization that displays nodes and vertices when editing. Essentially the purpose is: The Display Topology Nodes button will symbolize the ...
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50 views

Delete polygon underlap?

I am editing a layer in QGIS with severe polygon overlaps. Is there a way to delete the underlapping portions (i.e. the invisible parts) using QGIS? If I import the layer into GRASS using the ...
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29 views

QGIS : copy/paste with “Avoid Intersection” option

I need to copy and paste polygons from one layer to another but with adjustments in the pasted geometries: I need them to be cut in the same way they would have been cut by a single edit with the ...
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259 views

JTS - Java Topology Suite - Calculate radius from a given point

From point A, I want to check if a point B is within a certain radius from A. How calculate it usindo JTS? I tried this: Coordinate posicaoAtual = new Coordinate(-12.974900375893823, ...
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How do you split a feature using an existing line in QGIS?

All, Is there a way to split a feature (polygon) using an existing line (selected polyline) in QGIS? Thanks! -m
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213 views

How to handle/ avoid intersect errors when clipping the difference between two layers?

Using QGIS + Grass, I've added a shapefile of coastline and islands to my map. I then buffer this shapefile to create a coastal zone of a known width. At this stage the buffer consists of the ...
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From classified image to topology in ArcInfo

I have some coastal 4 band imagery that I have classified to designate land, water, and undetermined. I want to convert this to polygons with topology, and significantly simplify the polygons. If I ...
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261 views

topology rules for structuring topology data to get line feature as topoparent in topology graph

i Created topology graph of a polygon feature and i copied geometry of topology edges into line feature class,and topology nodes into point feature class i created topology layer containing ...
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v.clean in QGIS Python console

I have tried to use v.clean and v.clean.advanced (by GRASS GIS) within a script in QGIS, and was not able. I followed instructions here:, but was not able to do so. I got message: "No module named ...
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Point in Linefeature build through specific topology rules

i want to build Lines from Point Features following different topology rules (that lines aren't like randomly build, but how i should be following the extent from other polygons for example.. when ...
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Topology rules for a 3d network

I am currently writing a spec to which people may end up using to guide the digitization of a large 3d network (exterior pedestrian network + building interiors). In 2d network drawing, it seems to ...
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Dissolve a Geometric Network in ArcGIS

I have a geometric network of water mains in ArcGIS. It it composed of a line feature class. I would like to dissolve it based on whether line segments share common endpoints only. So basically ...
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Is it possible to compare two shape file if they have overlapped and gap between two data or not in QGIS

I am QGIS 2.0 user. I would like to compare two different shape file in the same region. This two shape file's outside border must be the same position. It means the overlap and gap must be zero. In ...
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36 views

The topology cannot be validated because it is checked out

when I try to validate an existing topologiy in my personal GDB I got this error "the topology cannot be validated because it is checked out". How to solve it? thanks! It is a personal GDB. I'm ...
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What does pgr_createTopology() expect for a table parameter?

In this sample http://docs.pgrouting.org/2.0/en/doc/src/developer/sampledata.html#sampledata there is this function: SELECT pgr_createTopology('edge_table',0.001); I understand that this creates a ...