Geographic Information Systems

Questions tagged [topology]

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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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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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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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1answer
39 views

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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22 views

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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1answer
72 views

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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2answers
68 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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102 views

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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45 views

Simplify/generalize vector geometry with side bias

I have contour polygons as vector geometry with attached elevation attributes. Is there a method to simplify vector polygons while preserving topology and elevation bias? By elevation bias I mean that ...
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35 views

Edit topology network

I have two SHP files in QGIS project (points: NODES.shp and lines: BRANCH.shp). NODES.shp has one ID attribute NODE_CON. BRANCH.shp has attributes NODE1 and NODE2 which represent start and end node of ...
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1answer
84 views

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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1answer
37 views

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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36 views

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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1answer
35 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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1answer
36 views

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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22 views

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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1answer
197 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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33 views

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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3answers
159 views

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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1answer
30 views

Customizing basemap in ArcMap

Using ArcGIS Desktop 10.7. I would like to customize the World Terrain Basemap in order to select which roads and topography labels appear. Is there a way to do this, and if not, then how would I ...
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50 views

How to include a tolerance when using QGIS topology checker

I'm using QGIS 3.14.3. The topology checker in this version doesn't seem to include a tolerance. I'm trying to relate points to lines by 'covered by' but keep getting errors.
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1answer
56 views

ArcGIS - Eliminating slivers/gaps automatically

I have a land map with three labels (sand, vegetation and water). I wish to eliminate overlaps and gaps between these labels. There are tens of thousands of gaps and overlaps, so I need to automate ...
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19 views

Can you define a topology rule between two feature classes from different feature datasets?

I work in a project that I want to define topology rules between feature classes from different feature datasets, is that possible ? if no is there a solution that can do that ?
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51 views

QGIS Features to polygons

I would like to know if there is any equivalent on QGIS for the ArcGIS function 'Features to Polygons': https://desktop.arcgis.com/en/arcmap/10.3/tools/data-management-toolbox/feature-to-polygon.htm ...
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24 views

topology: points closer each others + report

I have a point feature class structured like this: CompanyID | PersonalID | Lat | Long | 1 | 1 | ... | ... | 1 | 2 | ... | ... | 1 | 3 | ... | .....
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1answer
22 views

How to modify contiguity matrix in ArcGIS?

Is there any way to modify the contiguity relationships between the polygons in ArcGIS. I am thinking about a topology database that lets the user modify the data on the map? For example, if there is ...
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0answers
53 views

Automated polygon sliver removal

I am in the process of cleaning a large polygon dataset. This dataset represents the extents of an electrical network from a substation. The polygons have not been created correctly and there are ...
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1answer
118 views

v.generalize does not affect some boundaries

All in all, I would describe myself as a QGIS (3.12.2) beginner and have now contact with GRASS (7.8.2) for the first time. I want to simplify the boundaries of my polygons considering the topology. ...
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1answer
73 views

QGIS topology checker - check if point features are covered by line features

I want to use the topology checker to check if point features are covered by line features. For example are the bus stops covered by the bus lines.Therefore I use the topology checker with the ...
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35 views

Topology Checker for QGIS 3.x creating errors during validation process

I am looking to check for errors on my landcover layer in QGIS 3.x. I have used this same plugin for other projects, but for some reason am having issues running in on this specific layer. The issue ...
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23 views

QGIS - error added after processing

I use the "difference" processing beetwen 2 layers to have polygons of layers A that do not intersect polygons of layer B. In these 2 layers there are not bad geometries and topology is cleaned. I ...
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24 views

Geometry type error, Geometry Checker Plugin in QGIS

What does Geometry Checker Plugin return as "Geometry type" error? I launched the plugin with a polygonal file which obviously cannot contain lines or points, and return this error. Separately I have ...
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1answer
36 views

Problem with geometry checker plugin

I've used Geometry Checker Plugin to find some errors in my work. I have points that are connected to each other by lines. Among the parameters entered in the plugin there is "point covered by line". ...
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5answers
564 views

Find overlapping lines in same layer

I try to identify overlapping lines in the same layer with QGIS. My problem is that the lines are the same shape but not the same length. Maybe you can understand it with the picture below. These are ...
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0answers
20 views

ArcGIS tool to connect colinear polylines

I have a SHP file with thousands of polylines. Many are colinear (i.e., Line-A Endpoint-1 is same location as Line-B Endpoint-2). Sometimes they are colinaer across an intersection (as in image below),...
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45 views

Enforce Topology Check PostGIS

I would like to know if in PostGIS is possible to define spatial constraints for avoid topology errors? I have a polygon table and I need to avoid self-intersection and gaps. Does anyone know more ...
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1answer
125 views

Eliminating sliver polygons automatically [closed]

I have thousands of sliver polygons outside of my study area. What is the best way to eliminate them automatically? In ArcGIS or QGIS. Those polygon islands are an example of the slivers. Note: I can´...
2
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1answer
83 views

Creating difference polygons without overlapping topological errors

Using QGIS 3.12 (EPSG:27700) I am trying to create a polygon shapefile of features covering the 'blank' areas within a study area polygon that are not covered by a building and road polygon layer. I ...
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1answer
96 views

Snapping in QGIS

I have a Layer and I have lines as if they were the sidewalks, so for every street I have two lines. The problem is that some of the lines are not joined, how could I join them?
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2answers
310 views

Removing overlapping polygons in QGIS

How do I remove overlapping polygons in QGIS 3? I've tried v.clean (bpol, rmdupl and rmarea using right tolerances) and when I check the topology after doing that it says there is no overlapping but ...
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2answers
120 views

Keeping only internal borders in QGIS

I'm looking for the QGIS equivalent of TopoJSON's mesh function which goes through a vector layer and only keeps borders that are shared between multiple features. Here's an example of the output -- ...
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0answers
40 views

Topology rule for geometry in ArcGIS Pro

Is there anyway to write topology rule for the polygon geometry? I want nice rectangle, without any self-crossing lines. But sometimes I found those. So I want to use topology. I am adding an pic ...
2
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1answer
139 views

Errors when using QGIS Topology Checker with must not overlap rule

I use the Topology Checker Plugin in QGIS 3 with the rule "must not overlap" for a single PostGIS multipolygon layer. Can somebody explain the meaning of errors (colored in red) when the ...
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0answers
52 views

Model Builder ArcGIS - Export topology errors (Iteration Tool)

I was wondering if there’s any option to iterate export topology errors in ArcGIS model builder. My GDB Topology errors has all topologies within the same Topology dataset but model builder seems not ...
2
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1answer
126 views

Failing Unions due to Non-Noded Intersections

I'm trying to perform lots of unions in GeoPandas. I've got around fifty sets of between 7-12 GeoDataFrames of the same place at different times that I'm trying to union into one layer per set. Right ...
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3answers
246 views

How to find errors (gaps and overlaps) in a line feature class in ArcMap

I have a line feature class that contains roads that were manually edited. Now I want to check if all road crossings have been edited correctly. I want to check that there is no small gap or overlap (&...
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1answer
51 views

Using Topology in ArcGIS Desktop

I am using ArcGIS Desktop 10.6.1. I am trying to fix a dataset that has several holes throughout it. I built a topology to identify any area that does not have gaps or overlaps. However, when I run ...
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0answers
26 views

Setting topology rules to connect short lines aross complex intersections

I have a polyline SHP with a bunch of very short lines (less than one meter length). Is there an automated way to force the short lines to connect to a neighboring line at complex intersections? ...
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0answers
60 views

Road overlapping - ModelBuilder

I have a road feature class (in illustrations shown in gray color), each object in the attribute table has a "road_width" field with a numeric value, what width the road is. This feature class has ...
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0answers
64 views

Spatial join for adjacent polygons with same attributes

I am working with QGIS 3.4.5. I have a map of soil types (~ 100.000 polygons) and I'm trying to find the best way to make a spatial join with ~5000 point features with several numerical ...
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0answers
259 views

Avoid Overlap option not working in QGIS

I am creating polygons in a FGDB layer inside QGIS. I have topology on with advance options and have checked avoid overlap option for that layer. Still, I am getting overlap some times and some times ...

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