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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Fill polygon with circles
Essentially, I need these polygons to be circle packed with a varying degree of circles, using the red ones as an example.
The green polygons are represented as a canopy layer for a topology report. ...
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Extract a hierarchical topology from stream network
A typical stream network has a hierarchical topology that resembles a cladogram (phylogenetic tree). There are many software tools that have been developed to analyze variables along a cladogram, ...
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Removing true holes in a doughnut polygon
I want to create small cuts to open the holes in a shapefile, while the cuts should be contiguous without affecting the main shape and size of the polygons. The goal is not to have any true holes in a ...
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How to add topology to an existing feature dataset?
I have a GDB with a lot of data sets and layers(feature classes), I wrote a code to add a topology and validate a layer with that.
my code:
class Validate_Topology(object):
"""...
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When moving vertex node, change the shape of each polygon that contains this node in QGIS
I digitized a surveyor's map, creating many polygons in a 1:7000 scale so that all points are almost in their correct location.
I switch to a 1:1000 scale, both image and QGIS screen and want to fine-...
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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:
...
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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 ...
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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 ?
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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: ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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, ...
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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 ...
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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, ...
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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 ...
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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 ...
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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()) ...
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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 ...
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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"
...
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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 ...
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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 ...
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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,...
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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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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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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 ...
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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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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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