Questions tagged [topology]

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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Geometry error in large dataset

I have a large shapefile that I'm working on, containing more than 555.000 polygons, that represents the area covered by a 5G network. I have to extract areas that are not covered by a 5G network ...
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Merge several topology errors to largest in ArcGIS Pro

I searched first and found people who have come across a similar problem, however, they were trying to solve the errors by creating new features, and the solutions given where aimed at creating, so I'...
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PyQGIS - importing features selected by location from online GeoJSON file

There is a large GeoJSON file stored online with thousands of geometries and I have created and stored a simple polygon .shp file that is the area of interest. Is there a way to use PyQGIS to import ...
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Determining adjacency across elements in a GeoPandas GeoDataFrame

Main question What is an efficient (i.e., good balance of memory & processing time) way to compute adjacency using a GeoPandas GeoDataFrame? For my the rest of my question, I'll focus on the case ...
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Computing polygon-arc table and left-right polygon table in PostGIS

A classic data structure for describing the topology of a polygon layer is the polygon-arc table and left-right polygon table as described in the ArcGIS documentation and the following illustration ...
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PostGIS Topology result still has gaps and overlap

I have been trying to build a Topology in Postgis with 4000+ polygons. They are not cleaned, with a lot of gaps and overlaps. After using ST_MakeValid, creating the topology and adding topogeom column,...
2 votes
1 answer
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What exactly are the definitions of the boundary and interior of a line or a point?

Regarding the DE-9IM and the OGC spatial predicates for expressing relationships between two geometries; I'm wondering what exactly are the boundary and interior of respectively a line and a point? Is ...
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1 vote
1 answer
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Is the boundary of a polygon comprised in its interior?

I'm wondering, regarding the DE-9IM and the OGC spatial predicates for expressing relationships between two geometries; is the boundary of a polygon comprised in its interior or not? If not, does it ...
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1 answer
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How to add a polygon to multipolygon geometry in net topology suite?

I am missing something which seems obvious but does anyone know the answer? I have tried 'Append' method on MultiPolygon with Polygon geometry parameter but nothing happens. Would prefer to preserve ...
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3 votes
1 answer
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Are contiguity matrix and adjacency matrix the same?

I'm am sorry for that beginner question. To start the calculation of a spatial auto-correlation value, the book I'm reading writes that we will starting to construct a contiguity matrix. Looking at ...
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Tools in QGIS for cleaning polyline topology?

Are there polyline topology cleaning tools in QGIS that perform same as ET Geowizard's "Renode Polylines" and "Clean Dangling Nodes" ? https://www.ian-ko.com/ET_GeoWizards/...
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1 answer
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Fixing multiple gap errors within polygon shapefiles using ArcGIS Pro

I did a Land Use Land Cover Classification based on multiple and different source shapefiles. The problem I'm facing in the result now is that there a thousands (about 50.000) of little gaps which I ...
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Snapping parcels together using ArcGIS Pro

I need to work with parcel data that comes from a variety of sources (private, gov, etc.). A lot of this is bad data where polygon boundaries overlap or do not snap together. I am finding it ...
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Alignment in ArcMap

I have a lot of linear objects (green), the ends of which must match with some boundary (brown). I can do it manually using a snapping but there are too many lines. How can I do it automatically? I ...
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Editing rule file of Create Topology wizard

I was creating topology in the ArcGIS Pro topology creation wizard and I came across the following question: Is there any way I can save this topology rules sets and then edit it to use the rules for ...
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Parcel Topology continuously generating errors using ArcMap

I am using ArcMap. We have a geodatabase that stores roughly 110k parcel polygons, parcel boundary lines, and the topology layer. Currently, we have about 71k topology errors a majority of which that ...
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How to delete gaps but not change polygon boundaries with v.clean in QGIS?

So I am trying to get rid of gaps between a large number of polygons in QGIS using v.clean. I am able to successfully run the tool but the boundaries of very thin polygons end up changing quite ...
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In ArcGIS Pro, why are the colours of the polygons changing from a bright green to become greyed out as I zoom in?

Recently imported map from ArcMap to Pro, all the symbology has been brought over correctly. When zoomed out, I can see all polygons with the correct colours. The polygons are a Red/Green and can be ...
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2 votes
1 answer
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Lines connecting at vertices not included in ArcGIS Pro Network Analyst service area

Situation: I'm attempting to generate drivetime areas for a pedestrian walking network using Network Analyst in ArcGIS Pro 2.9. The walking network feature dataset has many lines from one feature ...
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Eliminating overlaps and gaps between polygons using ArcMap

I work in ArcMap 10.8 with an Advanced level license. I work with geological maps. In particular, the scale is 1:500000. I have a lot of line objects (different elements of a relief) that have common ...
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networkx line vertices as nodes

I read shapefile and converts it into a Graph using networkx and momepy as per documentation. networkx converts endpoints as nodes and the line as the edge, and disregard the vertices within the line. ...
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1 answer
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How to remove Topology Checker red dots?

How do I remove red dots created by topology checker? I was trying to check for overlapping lines within one layer by using the topology checker --> Must not have Dangles. This didn't work, I'm ...
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0 answers
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Find polyline end vertex on polyline edge

I am looking for a basic or best approach to find any polyline End-vertex that falls on the polyline Edge. I have a set of polyline data that shows the flow of electricity based on the Start and End ...
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1 answer
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Merging adjoining polygons by rule

I have a huge vector layer coming from an aerial image classification, containing lots of small polygons. I’m willing to clean it a bit (i.e. "removing" polygons < 25 sq. metres) but I ...
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Topolgy vs simple features

I'm starting using PostGIS, and then I found the main extensions of it, Simple Features (postgis), Topology (postgis_topology), Rasters(postgis_raster). The Topology extension is great, in some ...
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5 votes
3 answers
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Select polygons within polygons in same layer

I have a buildings layer that actually has a flaw. The inner courtyards, drawn as another polygon within the building polygon, should be islands of the building polygons. Instead, they are other ...
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6 votes
1 answer
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Selecting features that do not touch other features in same layer in QGIS

In QGIS I have a polygon layer where there are some isolated objects which do not touch other objects in the same layer. They are isolated and therefore I do not need them. How can I select these ones?...
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"M coord limit exceeded" error when clippling line to polygon (ArcMap 10.5)

I am running ArcGIS Desktop 10.5.1, and am trying to clip a large line feature (stream) using a single polygon extracted from a larger polygon layer (taxmap). Keep getting "Error 999999: Error ...
2 votes
0 answers
202 views

Tiny slivers and overlaps, even when using snapping when digitizing

I am in the process of creating several large shapefiles of administrative divisions in Europe. I digitized them using the snapping feature as well as the tracing feature. There are no visible ...
1 vote
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Seeking PostGIS equivalent of ArccGIS Desktop Integrate Tool

Is there a PostGIS equivalent to the ArcGIS "Integrate" tool for (multi)polygons? Basically it would be an extension of ST_SimplifyPreserveTopology, which instead of considering each feature ...
1 vote
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Creating custom topology rules in ArcGIS Pro

I am attempting to create Topology Rules in my project, because the existing topology rules in ArcGIS Pro are not enough for my requirements. Can I create custom topology rules in ArcGis Pro?
3 votes
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Automatically Remove Overlap using Error Inspector

I use Topology-rules and Error Inspector to remove errors in my map, duplicate lines etc. I often have hundreds of small errors. When available fixes are "Split" I can select all rows and ...
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3 votes
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Adjusting tolerance of topology checking using QGIS

I have a problem, the topology checker shows very tiny overlaps between polygons (under 0,000001 qm). For our project we just want to see detect the relevant overlaps, which are more than 0,01 qm. ...
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2 votes
1 answer
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Allow overlapping polygons in QGIS [closed]

When I draw a polygon in QGIS that overlaps an existing polygon from the same layer, QGIS automatically clips the overlapping area from the new polygon. Is there a setting to preserve the shape that I ...
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8 votes
3 answers
569 views

Redistributing duplicated points inside the polygon

I have a point layer with real estate data, obtained after geocoding by addresses. In case of multi apartment housing all points with data for several apartments in one building has identical ...
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1 vote
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Generating line features with "must not have dangles" constraint in QGIS

I am making line features in QGIS and sometimes, if I work inaccurate, they have dangels (loose ends). That is what I want to avoid. There are ways to detect dangles after creating a feature (topology ...
5 votes
2 answers
475 views

Topological editing of vertices that are common in two adjacent polygons in QGIS

How do you edit vertices that are common in two adjacent polygons in QGIS? I tried to select both polygons but when editing the vertex moves only in one polygon and not in both.
1 vote
1 answer
361 views

Maintaining topology on MultiLineString

I'm trying to get topological movement of lines with Leaflet-Geoman plugin using TopoJSON. There is a method called topojson.mesh , which Returns the GeoJSON MultiLineString geometry object ...
2 votes
1 answer
137 views

Showing the exact overlap area in Topology Checker QGIS

I am using the Topology checker in QGIS 3.10.11 to find overlaps in a large polygon layer. How can you get it to show you exactly where the overlap is? It just shows me there is an overlap somewhere ...
5 votes
1 answer
91 views

Unique attribute value across multiple layers

We are in the process of cleaning up our asset database which contains day 20 of layers generally in file geodatabase format and includes point, line and polygon types and some non spatial tables. Is ...
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3 votes
1 answer
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PostGIS TopologyException error when all polygons pass ST_IsValid test

I am getting this PostGIS error: ERROR: lwgeom_unaryunion_prec: GEOS Error: TopologyException: Ring > edge missing at 577690.01999999955 213605.69999999925 SQL state: XX000 I have checked that ...
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0 answers
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How to solve the error "ERROR 160196: Invalid Topology" when running the split tool

I am trying to split a multipart features using Split (Analysis) tool. When launching the process I come across the error message "ERROR 160196: Invalid Topology. Failed to execute split". ...
4 votes
2 answers
946 views

Why is v.clean not working?

I’m trying to clean the snapping errors from my line layer. I have a problem with running the tool and the outputs. During the run, many errors and warnings arise. I tried to use the tool in both UTM ...
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1 vote
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QGIS crashes when I try to check for double or check for crossing lines

I have a LineString layer that I want to check for double geometries and/or intersecting lines. I've tried two different tools (Check Geometry (Geometryprüfung) and Check Topology (Topologyprüfung)) ...
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1 answer
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v.clean what input feature type for polygon?

I have a polygon layer where the Topology Checker detects hundreds of overlaps and tiny gaps. So I want to use the v.clean tool to clean the topology. For cleaning, I selected the tools bpol, rmarea ...
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4 votes
2 answers
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Geometry vs geography vs spheroid for polygon-contains-point (PostgreSQL)

Many operations behave differently in geometry vs geography, e.g. the distance between two points. But what if I only need to check whether a polygon contains a point? Does that operation differ ...
1 vote
0 answers
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Split intersections of lines considering bridges and tunnels

I want to make a road network routable. I already have a road shapefile, but there are many intersections of lines that I want to split. Now I have two problems: (1) My first approach to split them ...
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3 votes
2 answers
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How to use v.clean in QGIS to fix polygon topology

I have QGIS 3.18 Zurich with GRASS 7.8.5 installed on my 64bit Windows machine. I have digitized 1600+ polygon boundaries that now have sliver polygons, gaps, and overlaps which I've confirmed via the ...
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8 votes
1 answer
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Changing drawing priority for selected feature in QGIS

I've noticed that the drawing priority of a selection, is lower than other records in the same table. That is - my record selection gets covered or hidden by unselected records. I haven't noticed this ...
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1 vote
1 answer
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Is topology stored explicitely in vector layers or is it derived from stored geometry information?

In vector layers, different types of information are stored like: Geoemtry Attribute data Meta data (like filename, projection etc.) Spatial indices However, what about topology? Is it an explicit ...
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