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Questions tagged [simplify]

A type of cartographic generalization in which the important characteristics of features are determined and unwanted detail is eliminated to retain clarity on a map whose scale has been reduced.

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25
votes
10answers
6k views

Existing solutions to automate generalisation/simplification of geographical data?

I am looking for existing solutions (softwares, libraries, methods, etc.) to automate the generalisation/simplification of geographical data as presented there, and also there. Do you know and use ...
16
votes
5answers
5k views

Simplifying polygons to linestring?

I would like to simplify some polygons that represent rivers into linestrings. I assume that holes in polygons can be omitted. Anybody has some good idea how to simply do it? It would be nice, if it ...
24
votes
4answers
5k views

Simplifying adjacent polygons using PostGIS?

I encountered a problem simplifying set of polygons that are adjacent. If I simplify each polygon separately with the Douglas–Peucker algorithm (which is used by many open source tools), the resulting ...
22
votes
5answers
2k views

Simplifying geometries (generalization)

What are the recommended ways of simplifying geometries? Keeping in mind projections, and simplifying state geometries for example. I've heard about converting to an 'equi-distant' projection that ...
8
votes
1answer
1k views

Cleaning large Shapefile using v.clean in order to dissolve features?

I'm having real problems cleaning up and reducing the size of a Shapefile which is published by the UK's Environment Agency. It shows the extents of the LiDAR open data they publish: each polygon is ...
4
votes
2answers
613 views

How to simplify streets such that seperate driving tracks are reduced?

Streets in Openstreetmap have more detail than I need. For instance I do not need seperate street tracks for each driving direction, instead I just want to show the general path of the street. Example:...
15
votes
3answers
3k views

Visualising clustered features in web maps?

I'm looking for the best symbol to display clustered features in the ArcGIS Server JS API. I don't like the "fly-out" animated cluster symbol, as used in the Silverlight API clustering or the JS ...
45
votes
2answers
11k views

Meaning of Simplify's tolerance parameter

The standard parameters of Douglas-Peucker's simplify algorithm are geometry and tolerance (e.g ST_Simplify in PostGIS). What's the meaning of the tolerance parameter? I know that the bigger the value,...
24
votes
5answers
3k views

How to simplify a routable network?

I have a network graph that I need to simplify in the sense of reducing the number of edges. The idea would be to merge nodes that are located close together and remove the connecting short edges. ...
13
votes
5answers
2k views

Large shapefile to raster

I have a large shapefile (1 gb) and need to rasterise it. I have tried the following already. 1.) Import it into GRASS using v.in.ogr this failed with the error message: ERROR: G_realloc: unable to ...
12
votes
2answers
14k views

writeOGR with a spatialpolygon simplified by gSimplify

I'm using gSimplify (rgeos package) to simplify the geometries of a shapefile. The funcion works good, but now I can't write the output in a new shapefile. I tried some ways: writeOGR(simplyshape, ...
4
votes
2answers
11k views

Removing unnecessary vertices?

I have over sampled polygons that I need to simplify, without changing the shape. basically, I want to reduce the number of vertices, by eliminating the ones that are useless and have the polygons ...
3
votes
4answers
1k views

Redistribute linestring vertices to specified distance

I use a groundwater model program called GMS, and it has a very useful function "Redistribute vertices" (more info). I use this function all the time to both simplify and provide regular spacings ...
4
votes
2answers
4k views

Simplify Raster Contours ArcGIS 10

Does anybody know a way to simplify a number of contour polylines derived from a raster dataset? I need to generate a map that shows contour polylines at relatively small scale. With the contour ...
1
vote
1answer
245 views

Simplifying multiple lines to create central axis?

I have a layer with railway lines, downloaded from OpenStreetMap. Every single track is represented separately, so at trainstations, you have several parallel lines, as well as sidelines that lead to ...
9
votes
1answer
1k views

How to Simplify a Line Network Preserving Topology?

I have a Shapefile (consisting of European major roads) with about 250.000 Segments which I have to simplify for pgrouting. But I can't seem to find a way to do that properly. This is what it looks ...
9
votes
2answers
8k views

What is “Simplify tolerance” in QGIS's Simplify geometries tool?

I am trying to use QGIS 2.8 to simplify vector geometries. But I do not understand the significance of the Simplify tolerance value in the Simplify geometries tool. The documentation does not ...
7
votes
1answer
2k views

Why do simplify polygon results differ between ArcGIS for Desktop and PostGIS?

I am mainly interested in why and how the Simplify Polygons tool in ArcGIS for Desktop handles the simplification process, including preventing and resolving topological errors better than the ...
2
votes
1answer
943 views

Merging close lines?

I downloaded some road network data derived from OSM by GeoFabrik, see the initial state: Near Székesfehérvár (Hungary), parallel lines are probably trunk or motorway roads. I would like to simplify ...
14
votes
1answer
6k views

Simplify polygons of sf object

How do I simplify an sf polygon without introducing gaps and slivers? With a shapefile, for example, I would use rmapshaper::ms_simplify(): library("pryr") library("rgdal") library("rmapshaper") ...
4
votes
1answer
2k views

How to maintain right-angles when buffering?

When buffering some polygons I am trying to avoid the curved buffered area like this: I'm trying to do thins within an FME workbench but if someone knows how its done in other software that would ...
1
vote
0answers
117 views

How can I use ST_Contains/ST_Overlaps with non-simple lines?

Following the SQL of the accepted answer to How to get smallest line segments from intersection + difference of multiple overlapping lines? copied below. I'm having some difficulties assign the ids of ...
1
vote
1answer
919 views

Algorithm to move polygon nodes when simplifying

I want to simplify polygons that come from a raster analysis. In order to avoid overlap and gaps, I first convert my polygons to lines. The problem is that all algorithm are then keeping the two end ...
3
votes
3answers
3k views

Simplifying Shapefile using ArcGIS Desktop or alternative?

I have a shapefile that contains neighborhood boundaries that I want to simplify. Right now I am thinking of converting the shapefile to Google maps KML so I can insert the boundaries into the map as ...
2
votes
0answers
322 views

'.Simplify' causes 'null geometry' errors (Python, OGR)

Question relates to an earlier one: Can't retrieve geometry (Python, OGR, Rtree) Im trying to simplify a dataset with 180k+ polygons and place the simplified geometries in a separate dataset. ...
2
votes
0answers
269 views

Simplify by number of points in QGIS

I have a fairly simply question about something I just don't know how to do. I am aware you are able to simplify polygons in QGIS based on distance tolerance but my questions is, is there a way to ...
2
votes
3answers
677 views

How to break apart a complex line segment into simple line segments between all points?

Take for instance a very complex line string.. which has WKT like this LINESTRING(1 1,2 2,3 3,4 4,5 5 ...) I want to create two-point linestrings from many-point linestrings. SELECT ST_MakeLine(...