Tagged Questions

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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2
votes
1answer
174 views

How can I make the topology checker plugin ignore very tiny errors?

I'm a QGIS2.0 user. Topology checkers is a very valuable for me as a data creator. I use this plugin for checking data quality. But, this plugin finds too much errors include very, very tiny ...
0
votes
0answers
81 views

Dissolve a Geometric Network in ArcGIS

I have a geometric network of water mains in ArcGIS. It it composed of a line feature class. I would like to dissolve it based on whether line segments share common endpoints only. So basically ...
1
vote
0answers
45 views

How can I build a network from a latitude, longitude points? [closed]

How can I build a network from a latitude, longitude points? I have some points(latitude and longitude) and i wish to build my network based on this points.
0
votes
0answers
44 views

Is it possible to compare two shape file if they have overlapped and gap between two data or not in QGIS

I am QGIS 2.0 user. I would like to compare two different shape file in the same region. This two shape file's outside border must be the same position. It means the overlap and gap must be zero. In ...
0
votes
0answers
39 views

The topology cannot be validated because it is checked out

when I try to validate an existing topologiy in my personal GDB I got this error "the topology cannot be validated because it is checked out". How to solve it? thanks! It is a personal GDB. I'm ...
0
votes
0answers
113 views

What does pgr_createTopology() expect for a table parameter?

In this sample http://docs.pgrouting.org/2.0/en/doc/src/developer/sampledata.html#sampledata there is this function: SELECT pgr_createTopology('edge_table',0.001); I understand that this creates a ...
5
votes
2answers
828 views

I would like to know how to clean topological errors

I am a new QGIS 2.0 user. I was so impressed the new default tool, Topology Checker, in this new version. But, hundreds errors are bothering me for cleaning up features. Is it possible to clean ...
2
votes
3answers
144 views

How to correct topology on a shared boundary by removing nodes from a feature?

Maybe you can help me solve a problem regarding topology cleanup that I recently came a cross. I have two layers with bunch of polygons (or feature classes as I'm in the ESRI world) that should share ...
1
vote
0answers
196 views

Vertex and Nodes Tool - Migrating from 9.3.1 to 10.2.1

A previous employee built a custom tool for users in our organization that displays nodes and vertices when editing. Essentially the purpose is: The Display Topology Nodes button will symbolize the ...
4
votes
4answers
253 views

Is there a way to snap to apparent intersections in ArcGIS 10.1+?

Suppose there are two lines in an ArcMap 10.1 or 10.2 editing session that cross but do not intersect, per se. This is the case when new lines a drawn. Is there a way to snap to the point where the ...
2
votes
1answer
100 views

measuring adjacency between polygons

I am working with some land ownership data. I would like to identify parcels the have small adjacency between other parcels. In a nutshell I want to identify where there is a small overlap between ...
2
votes
2answers
148 views

How to check if vertex exists (on polyline) based on location of point layer using ArcPy?

Using ArcGIS for Desktop Advanced 10.1 (with all extensions) I am building a centerline network that will be used by a MapObjects program to do routing based on "turns at any vertex" (as opposed to ...
5
votes
0answers
98 views

What PostGIS [topology] provided tools may be used for data quality assurance?

I'm learning about techniques to ensure GIS data quality. Googling around, I've found a few papers about theory and best practices (here and here), and a couple of short presentations about the topic ...
2
votes
2answers
416 views

Doubts about how pgRouting topology is built and how flexible it is

I'm learning pgRouting, to validate if it can be used in a project. I have several doubts. Mostly related with how could I "fill the gap" between the "bricks" it provides and the real world ...
2
votes
0answers
83 views

Is there a way to build topology and work with topology relations in PyQGIS?

Is there a way to build topology and work with topology relations in PyQGIS? I'm asking because I need to run some custom generalization algorithms on my data, and I need to preserve topology. ...
1
vote
1answer
286 views

Insert Vertex into Polyline based on Point layer using arcpy

This is essentially the same question asked here that was not answered... Using ArcGIS 10.1 Advanced I have a point layer with points that represent the intersection of a driveway with a street ...
1
vote
1answer
97 views

ESRI ArcMap Topology rules on multi story buildings

I would like to run some topology rules to find snapping errors in our polygons but I am running in to the problem where we are working on multi story buildings with every polygon regardless of floor ...
5
votes
2answers
504 views

What's the difference between hypsography and topography?

I've recently come across some data that has been labeled "hypsography". I looked it up and it sounds like topography. But this data source has data labeled "topography" separate from its ...
1
vote
1answer
149 views

Problem when creating database based on template_postgis

I have created a PostGIS template but when I try to create a database based on this template this is what happens: Connecting to the template: \c template_postgis; You are now connected to database ...
3
votes
5answers
816 views

How to Identify and Delete duplicate vertices?

I am trying to figure out how to delete duplicate vertices. I have successfully determined that there are duplicate vertices using PLTS Data Reviewer, but I am confounded as to how I identify and ...
1
vote
0answers
51 views

Delete polygon underlap?

I am editing a layer in QGIS with severe polygon overlaps. Is there a way to delete the underlapping portions (i.e. the invisible parts) using QGIS? If I import the layer into GRASS using the ...
6
votes
3answers
2k views

How to fill a hole in a multi-polygon layer on QGIS 2?

I need to fill a hole in a multi-polygon layer on QGIS 2.0. I've set the snapping option for the layer as follows : mode: to vertex and segment tolerance 4 pixels avoid intersection "enabled" ...
2
votes
0answers
80 views

Is the TIN created out of several cross sections different from merging the TINs created out of each set of two cross sections?

I have a river with cross sections that have the water surface elevation values. I am trying to create TIN from the water surface values and then compare it with the topo (to see the flooded areas). I ...
1
vote
0answers
33 views

QGIS : copy/paste with “Avoid Intersection” option

I need to copy and paste polygons from one layer to another but with adjustments in the pasted geometries: I need them to be cut in the same way they would have been cut by a single edit with the ...
2
votes
0answers
206 views

GeoDatabase topology and rules with a *.rul file

I have been working for some time on a solution to a problem much like this question. I have several layers that I want to resolve together. I have them all in topology (geodatabase) and have been ...
11
votes
1answer
759 views

What is topojson and how is it different than geojson?

This is a conceptual question. What are the differences between these? and what are the pros and cons of these formats?
3
votes
3answers
197 views

How to identify misaligned corners in PLSS sections

Sometimes PLSS section corners do not align How could I automate the detection of these corners and generate a new shapefile showing where this occurs? I have a shapefile of 147k section polygons ...
1
vote
1answer
131 views

ArcView: Trim polyline, that is shorter than specific dangle length (alternative to tool: Trim Line)?

I am looking for a way to trim dangles from a polyline shape, that are shorter than a specific length like the Trim Line Tool for ArcEditor and ArcInfo, but with ArcView-License. I already discover, ...
2
votes
1answer
175 views

GRASS - v.clean Conflation - How to snap a layer to a base layer

Someone told me in this post that GRASS GIS can handle multilayer topology, what I have not found any information about. I am not a specialist of GRASS GIS so I would need help with that if its really ...
9
votes
2answers
507 views

Are there Desktop GIS alternatives to ArcGIS 10.X for topology and vector conflation?

Is there any options other than ArcGIS for Desktop for topological rules and automatic topology integrity enforcing in a Desktop GIS? I am looking for something that will automatically snap features ...
1
vote
0answers
326 views

JTS - Java Topology Suite - Calculate radius from a given point

From point A, I want to check if a point B is within a certain radius from A. How calculate it usindo JTS? I tried this: Coordinate posicaoAtual = new Coordinate(-12.974900375893823, ...
2
votes
1answer
162 views

Tools/Script to reshape automaticaly topologic edges within a given distance in ArcGis 10?

I have a footprint feature class and a land use cluster feature class. I am looking for a method/tool/script that would allow me: to reshape two edges into one (topologically) to decide at which ...
4
votes
3answers
502 views

Create a network topology for pgrouting with grade separation

I have built a network using Ordnance Survey's ITN data and I can solve routes across the network. What I need is to build in grade separation topology for overpasses and underpasses on the network so ...
4
votes
0answers
220 views

How to create a topologically correct dataset in PostGIS (with GRASS)?

I have shapefiles which I have loaded in postgis and now i am trying to use geometric function in postgis like ST_intersect and they fail because the data is not topological correct. I have tried to ...
4
votes
0answers
125 views

Joining layers with respective elements with PostGIS Topology

Recently I have started using PostGIS topology extension, but I have some difficulties in understanding how the structure works: One of the key points is the use of "layer"s: as of what I understand, ...
5
votes
3answers
556 views

Snapping start- and end nodes of lines to other lines in PostGIS

There are plenty examples that show how to snap lines to points, but I haven't been able to find any (fast!) way of snapping the start- and end nodes of line strings to nodes of other lines. ...
3
votes
3answers
496 views

How to clean layers from non topological databases?

I'm doing my internship in a consulting office which is switching from MapInfo to QGIS/GRASS 1.8.0. I posted here a few days ago about the way to clean a polyline from a Lidar data with v.clean. ...
4
votes
1answer
494 views

How to repair and clean contours from high data resolution (lidar)?

I'm unsuccessfully trying to make a bathymetric map with contours extracted from Lidar data at 1 m resolution. The extracted contours have a lot of artifacts like dangles and islands. First I used ...
3
votes
1answer
147 views

How can i topologically sort 2D triangles and put in an array?

I have a set of 2D triangles in a Geometry array which together forms a connected strip when placed them according to edge adjacency. However, in the array they are not in topological order based on ...
5
votes
3answers
1k views

How tool to split polylines into two-part lines at vertices in ArcGIS for Desktop 10.1?

I'm using ArcGIS 10.1 SP1 at and we have a problem. There is a serious topology bug that I've mentioned in another question that is affecting our workflow. At present, Esri has stated the fix will be ...
1
vote
0answers
73 views

How do you split a feature using an existing line in QGIS?

All, Is there a way to split a feature (polygon) using an existing line (selected polyline) in QGIS? Thanks! -m
2
votes
1answer
333 views

need help for script checking topology using ogr in python

My main goal is to create a new feature indicating if the line features intersect each other as well as if they are not connected to a feature. My problem is how to identify the intersecting and not ...
2
votes
1answer
509 views

Grass v.clean.snap with Polygons

I am doing some topology testing using Grass in QGIS. I am hoping to snap nodes to eliminate gaps between polygons. When I use the v.clean.snap function in Grass it does not work on polygons. When I ...
4
votes
1answer
327 views

Topology problems with QGIS/GRASS

*edited file links below I'm working on several NGO projects at the moment, all of which are reliant on being able to use a district level map with some 490+ features, and I am running into some ...
4
votes
2answers
76 views

How to store and edit data with a defined topology using open software and formats?

I'm looking for a way to store and edit spatial data that preserves topological information. In my concrete application, I need to represent triangular meshes, which consist of unique nodes and ...
7
votes
3answers
5k views

How to analyze differences between two shape files and put results into a new shape?

I have two polygon shape files of the same region from two different years (1985 and 1997) and I need to analyse the differences between the two shapes resulting in a third polygon shape file ...
0
votes
3answers
462 views

How can I easily detect gaps in a polyline using arcmap 10.0 (arcview license)?

I'm making routes by selecting links from a streets layer which I export as a new temporarely layer in arcmap 10. This layer which I call route_temp unfortunately can be very long and contain gaps, ...
3
votes
1answer
109 views

Learning resources for beginning differential topology for a programmer? [closed]

With this question I'm looking for suggestions about how and where to start learning differential topology starting from a good base of linear algebra and geometry, also consider that this know-how is ...
4
votes
1answer
289 views

Simplification algorithms for 3D topology

My problem is about simplifying a given topology that can be opened ( an usual 3D reconstruction of a given square on a map ), totally closed (like a perfect sphere) or a topology with holes ( a ...
3
votes
4answers
394 views

How can I create polygons of the area surrounded by roads / lines?

I'm currently trying to create polygons that represent the areas surrounded by roads. The roads are stored in PostGIS as points / lines so I have flexibility over what I can do with them. I'm ...