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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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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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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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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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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Systematically marking all roads in parcel database as exception in "no gap" rules in topology

How do I systematically mark all roads in parcel database as exception in "no gap" rules in topology? I also hope to mark some overlap condo parcels as " exception" to no overlap ...
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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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3 answers
239 views

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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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 ...
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Finding(drawing) interior, boundary and closure of given 2D visual representation of topological space

I'm currently studying for my exam in Geospatial Databases. We're given a visual topological space (picture below) and we need to draw the interior, boundary and closure of this space. I understand ...
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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 ...
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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 ...
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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?
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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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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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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
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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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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 ...
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5 votes
2 answers
259 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.
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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 ...
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1 answer
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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 ...
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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
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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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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". ...
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3 votes
2 answers
420 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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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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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 ...
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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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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
152 views

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
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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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4 votes
1 answer
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Problems with cleaning the topology of a shapefile using GRASS tools and snapping tools

I have a shapefile with almost 1000 polygons (each polygon representing a farm). There are a lot of topological errors (gaps/slivers and overlaps between polygons). Below is a "zoomed in" ...
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5 votes
1 answer
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Determine whether a polygon is completely surrounded using QGIS [closed]

I have a shapefile dataset of polygons. I would like to find those polygons that are completely surrounded/enclosed. Mathematically, this means that the perimeter of Polygon A should equal the sum of ...
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Identifying topology error with Javascript

ArcGIS has tool to fix topology errors. Does any JavaScript gis package have similar function? I have tried two packages. OpenLayers has the function to build topology from geojson TopoJson can ...
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3 votes
1 answer
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Making vector geometries "Kiss" in QGIS

I am working with vector geometries that I recently simplified using the native:simplifygeometries method in the processing toolbox. I am pleased with the simplification but I want to "fill" ...
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0 votes
2 answers
385 views

Simplify polyline by arcs and lines

I work in the construction industry and have a couple of software tools specific for the field, namely AutoDesk products Revit, AutoCAD and Civil. Presently, I have come across the problem of ...
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Error while removing gaps with v.clean in QGIS

I have a polygon layer (Geopackage with 378 features in EPSG:3857) with many very small gaps between them (topology checker lists more than 5000). The gaps are in a range of several hundred meters to ...
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6 votes
1 answer
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How can I split my polygon file into topological boundaries?

This question was asked 8 years ago, but the algorithm in the accepted answer is gone. (How do I split polygons into line segments?) So how can I split my polygon file into "segements"? The ...
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1 vote
1 answer
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Snapping two topology layers together based on point

In QGIS 3.14.15 with GRASS 7.8.3 I have two layers both with correct topology that function how they should. When using the Network Analysis > Service Area tool, they work as they are supposed to. ...
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0 votes
2 answers
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Polygon topology validation in ArcGIS - whole study area artefact problem

I have no experience with topology validation in ArcGIS. I have polygon feature class. When I create topology for this feature class, I specify two topology rules : Must Not Overlap Must Not have ...
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3 votes
1 answer
133 views

Moving point feature and vertex from polyline at the same time

I have two layers in QGIS 3.14: one with point geometry one with polyline geometry The point geometries (p) have the same coordinates as some of the polyline vertices (v): (v)--------(v)----------(v/...
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3 votes
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Finding intersection errors based on attribute value using ArcGIS Desktop

I have a road network table in a PostgreSQL database. The table has a level attribute which marks if a road is on the surface or if it is an under- or overpass. I would like to check the topology of ...
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How can you completely cover the surface of a raster with circles where the radius of the circle is the raster value at its centroid?

This is more of an algorithmic/math problem, but I was wondering if someone could point me in the right direction. There's the common problem of covering a surface with circles of equal sizes, but ...
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5 votes
1 answer
756 views

Export topology checker results as table/shapefile in QGIS

I have used the plugin "topology checker" and I got table with all the topology errors : I would like to save this table as new layer/ csv or any way I can export it. I saw there were ...
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1 vote
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Finding the LineString Corresponding to a Certain Road in a Roads Database

I am using tiger line road data to find roads that runs through certain points. I know what road is immediately next to the point by the road name and road type. What I currently do is grab all the ...
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4 votes
3 answers
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Solving Traveling Salesman-like Problem

I own a (very) small appliance service company. It's just me. I cover roughly a 20 mile radius from a my office. Customers can sign up on my website for service calls anywhere within my service area. ...
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