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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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Preventing polygons from overlapping after splitting them in QGIS

I have a FileGDB with several polygons. When I split them using the Split Features-Tool, they overlap with other polygons within the same layer I did not split. Here are some screenshots: Original: ...
Motti's user avatar
  • 466
1 vote
0 answers
36 views

How to create line topology from-node to-node table fields?

We are looking for a way to create line topology from-node and to-node attribute fields on a shape file as shown below. We know that ArcHydroTools GenerateFNodeTNode can do it, but want to avoid ...
jger's user avatar
  • 137
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0 answers
37 views

Bulk-removing self-overlapping polygons

Using QGIS 3.18, I ran the topology checker on a polygon layer (gpkg format). It found several thousands self-intersections. I can see the errors, but I cannot seem to be able to delete the polygons ? ...
rdelattr's user avatar
1 vote
1 answer
51 views

Finding lines that fold over themselves

I'm working with a dataset provided by a third party and have found some lines that fold back on themselves (or in some cases, almost fold back on themselves) For example, this line folds back over ...
Midavalo's user avatar
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0 votes
1 answer
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QGIS Having an issue with v.clean/snap removing existing geometries when trying to snap undershoots

I'm running v.clean on a merge of 2 vector layers of pipeline data. I initially found the issue trying to clean undershot laterals not properly attached to main lines, scale is undershot by about 1 ...
Derek_P's user avatar
  • 343
0 votes
1 answer
65 views

Node information in a PostGIS dataset

I am working in QGIS / PostGIS to plan the cable layout for a seismic array. The power distribution is from the green point with the white cross in the middle. The nine green points marked with a ...
MortenSickel's user avatar
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0 answers
18 views

Topology checker won't highlight in red the overlaps

I´m using QGIS and trying to find overlaps in a shapefile. When I use the Topology Checker I get 24 results for overlaps, but they are not highlighted in red as they used to the last times I did the ...
Gonçalo Coimbra's user avatar
3 votes
0 answers
95 views

Topology-aware "waviness" for polygons in QGIS

I am wondering if there is any chance to create "wavy" polygons that respect the topology. In a polygon-layer where the individual features shares boundaries you can easily style each ...
Lenn's user avatar
  • 1,297
0 votes
1 answer
41 views

ArcGIS Pro - routing, remove short network elements and reconnect edges

I am setting up an ArcGIS Pro network for use in Network Analyst. So far things work pretty well, depart from some 1600 errors due to this kind of problem: " SourceName: linknetz, ObjectID: ...
robert tuw's user avatar
0 votes
0 answers
46 views

Select building facades that face the street

I have a set of buildings (building footprints) and a street network. The buildings have attribute Use. I need to transfer the value of attribute Use as well as the length of the building façade that ...
Jio's user avatar
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3 votes
0 answers
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Are there ways to speed up building large topology datasets in PostgreSQL/PostGIS?

I used this stored procedure to create a topology for all Census block groups in the contiguous US. It took almost 136 hours to run (on a fast, dedicated workstation - Ubuntu 23.04, PostgreSQL 16, 128 ...
Stonetip's user avatar
  • 187
4 votes
2 answers
343 views

Cryptic PostGIS/GEOS topology error

I'm attempting to determine 1) what "ring edge missing" means in the following PostGIS/GEOS error message, and 2) why ST_Intersection throws it for certain gridSize parameters but not for ...
Geolographist's user avatar
0 votes
1 answer
71 views

Vector layer is showing gap which is not marked in red, how to correct the problem [closed]

I am working in a QGIS layer with more than 450 polygons. When I am checking with the topology checker for any error, it shows two gaps, but they are not visible in red, and one polygon is being ...
Neelanjan Paul's user avatar
0 votes
0 answers
123 views

Quickly remove overlaps from two polygon layers in ArcGIS Pro

I have two polygon layers (both very large, up to 1 million rows). One is cadastre (lot boundaries) and the other is building footprints. The latter is rather inaccurate (MS / Daylight layers but is ...
heather_sea's user avatar
1 vote
0 answers
166 views

How to resolve dangling end between two lines using QGIS

(It goes without saying, I am a beginner with all of this!) I have a QGIS (version 3.28.11-Firenze) file into which I imported a KMZ from Google Earth. The purpose of this is to produce a shapefile ...
Matt Greer's user avatar
3 votes
0 answers
116 views

Topology checker shows gap which is not marked in red and not identifiable

I have a project with more than 100 polygons. I used Topology checker to identify errors like Gaps, Overlaps, Invalid Geometries, and Multi part features and corrected them all. The process was ...
sunil dev's user avatar
0 votes
1 answer
48 views

QGIS split feature tool produce topology gap errors while using Digitize with Curve

I'm using QGIS to digitize an area for land-use classification. The problem occurs when I start editing and use the split feature tool to split any polygon using Digitize with Curve Tool. When I check ...
MU Rehan's user avatar
1 vote
0 answers
53 views

PostGIS / ST_Intersection error GEOSIntersects: TopologyException [duplicate]

With PostGIS, I want to generate a new table being the result of the intersection of a table of mixed geometries and a polygonal layer. Here is my attempt. I think this request is valid. But I have an ...
user35117's user avatar
  • 929
0 votes
0 answers
34 views

Self-intersections from geoprocessing in QGIS but detected via digitizing validity checks

I have performed a set of geoprocessing tasks to produce a polygon output. The polygon output contains - what I would consider an invalid set of vertexes and as such, an invalid geometry. (see screen ...
nr_aus's user avatar
  • 3,576
2 votes
1 answer
66 views

PostGIS ST_Overlap does not allow attribute editing

I have a PostGIS database which has a wonderful topology rule (ST_overlap), implemented following "dbaston"s suggestions in this post: Enforce PostGIS constraint that geometries do not ...
KoGIS's user avatar
  • 33
1 vote
0 answers
102 views

How to simplify a segmented line network based on smallest angles at connection points?

I´d like to simplify a network of lines by merging small segments into interconnected compartements. The algorithm should merge the lines based on the smallest cost (degree) at the junction points to ...
mapmap's user avatar
  • 53
2 votes
0 answers
82 views

Intersecting multiple overlaping polygon tables in PostGIS

I have a seven linestring tables that I buffered to create polygons of each line network. I then successively intersected each table (Figure 1 below). I use the following sql query, but it take 36 ...
MJM's user avatar
  • 995
-1 votes
1 answer
251 views

Rigorously validate a GeoJSON polygon

I have a GeoJSON polygon which I'm suspicious about. It doesn't render properly in several different tools. Mapbox's Geojson-hint gives it a clean bill of health. The shape has many internal holes, ...
Steve Bennett's user avatar
1 vote
1 answer
323 views

Align features of polygon process not making changes in ArcGIS Pro

I have a layer of 770 polyons (LWS) which are generally not aligned to OS Mastermap but mostly should be. I am trying to use the Align Features tool to bring the LWS polygon boundaries that are less ...
gordon26b's user avatar
0 votes
1 answer
89 views

v.clean (GRASS) creates additional features

I am working with a large road dataset (approx. 1 million features) with a high number of overshoots and dangles. To address the overshoots and dangles, I am using the v.clean tools (break, snap, ...
Julia Cardwell's user avatar
1 vote
0 answers
57 views

Polygons sharing a vertex causes gaps in topology

I have created a floodplain with raster to polygon, smoothing/simplifying, dissolving, and repairing geometry after every geoprocess. Now I'm doing a topology check for must not have gaps and it has ...
Tebetheia's user avatar
0 votes
1 answer
141 views

Topology rules with attribute table exceptions in ArcMap/ArcGIS Pro

I have a set of geometries that represent different surveying polygons, for each set I have certain features that are exactly the same geometry wise, but have a different value in a unique identifier ...
Rodrigo Suárez Castaño's user avatar
3 votes
2 answers
92 views

PyQGIS: How to find out if point is before, beneath or after a line geometry

I have got a line dataset and a point dataset and I wrote a function that snaps every point onto the closest line. My data look like that: However, the function I use (QgsGeometry.nearestPoint()) ...
fuzzysolutions's user avatar
2 votes
0 answers
72 views

MultiPolygon - removing polygons intersections in PostGIS [closed]

Having a MultiPolygon, I would like to get a MultiPolygon where each polygon has no 'holes' and there are no polygons intersecting with each other. How to achieve this in PostGIS? To give you an ...
Marcin K's user avatar
2 votes
0 answers
69 views

Table not found in AddRuleToTopology

The following code works as expected in an ArcGIS Notebook (2.9.x): # variables arcpy.env.workspace = r"\\foo\Staging\NG911.gdb\ESINET" staging = r"\\foo\Staging\NG911.gdb\ESINET" ...
bagration's user avatar
2 votes
0 answers
135 views

PostGIS Topology with ArcGIS, is it possible? [closed]

I have been tasked with developing a specialised asset management system, based on PostgreSQL/PostGIS given that it will be multi-user reading and editing, that will be consumed by and manipulated ...
Madeleine's user avatar
1 vote
1 answer
195 views

Checking topological errors in Esri geodatabase feature class using ArcPy

I am using PyScripter and ArcMap import arcpy # set up workspace and input feature class arcpy.env.workspace = r"H:\Data_Processing\Work\PL07\Mygdb.gdb" fc = "County" # create a ...
GrizzlyBear's user avatar
1 vote
0 answers
98 views

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 ...
Elenica's user avatar
  • 41
2 votes
0 answers
138 views

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'...
Dan's user avatar
  • 31
0 votes
0 answers
38 views

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 ...
HyPhens's user avatar
  • 518
0 votes
1 answer
633 views

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 ...
Felipe D.'s user avatar
  • 2,699
2 votes
2 answers
486 views

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 ...
tinlyx's user avatar
  • 11.1k
5 votes
0 answers
210 views

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,...
Riceiceice's user avatar
2 votes
1 answer
460 views

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 ...
swiss_knight's user avatar
  • 10.5k
1 vote
1 answer
68 views

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 ...
swiss_knight's user avatar
  • 10.5k
0 votes
1 answer
715 views

How to add a polygon to multipolygon geometry in NetTopologySuite?

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 ...
Kumbra's user avatar
  • 470
3 votes
1 answer
239 views

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 ...
Marc Le Bihan's user avatar
1 vote
0 answers
192 views

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/...
sirgeo's user avatar
  • 2,049
1 vote
1 answer
440 views

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 ...
Radde1683's user avatar
  • 193
0 votes
0 answers
173 views

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 ...
erik_r's user avatar
  • 1
0 votes
0 answers
178 views

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 ...
Ian Moffit's user avatar
0 votes
0 answers
323 views

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 ...
Abel's user avatar
  • 1
2 votes
1 answer
149 views

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 ...
cajuna's user avatar
  • 21
1 vote
0 answers
82 views

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 ...
Ярослав Вингард's user avatar
0 votes
1 answer
478 views

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. ...
sutan's user avatar
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