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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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2
votes
1answer
41 views

Simplify Slider

QGIS 3.4 appeared to have a slider for adjusting the simplification tolerance - at least that is what shows up in the 3.4 documentation, for example: https://docs.qgis.org/3.4/en/docs/training_manual/...
11
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1answer
748 views

Simplify the straight sections of (multi)Linestring in PostgreSQL/PostGIS leaving the curved sections untouched

I have (multi)linestrings containing upwards of 5000 points and I want to perform two simplifications possibly using Ramer Douglas Peucker or alternative methods in PostGIS. The (multi)linestrings ...
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2answers
25 views

Reducing coordinate decimal places in WKT using C#?

I have imported several shapefiles into a Microsoft SQL Server 2017 database When I use the STAsText() function on geography objects I get the following WKT: SELECT [Adm0GeoBoundaryID] ,[...
2
votes
1answer
53 views

Original polygon is completely contained by new after simplifying

Is there a polygon simplification method that can create a polygon, such that the original is completely contained by the new one? The aim is to create the new polygon from as few points as possible ...
1
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2answers
39 views

Can't simplify track with gpsbabel

I have a MultiLinesString layer in a geopackage that I want to import to a Garmin GPS as a track. I exported the layer from QGIS as a .gdb. However, it's too long to import to the GPS (~2500 points, ...
0
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1answer
206 views

ArcGIS Raster To Multipoint Mac/OSX alternative

Is there an alternative to the ArcGIS Raster To Multipoint tool for Macs? The VIP thinning method is particularly of use. A comparative point cloud thinning/simplification tool to this would just as ...
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 ...
2
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0answers
56 views

Wang's Bend Simplify in QGIS

I am looking for an alternative to ESRI's Simplify Polygons - Bend Simplify method (I only have a Basic License). Is there an existing QGIS plugin which supports this specific polygon simplifying ...
0
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0answers
44 views

Simplifying Mapbox vector tiles from GeoServer for beter performnce?

I use MapBox Vector tiles from GeoServer on my open source web site. How can I improve the performance of this service and how can I simplify the geometry of this service for performance? I know that ...
1
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0answers
47 views

Simplifying Multiple neighbouring Polygons, removing gaps and overlaps

My main goal is to simplify multiple polygons, avoiding overlaps and gaps between them. My initial approach was: Find intersections for each polygon so that I end up with an array of polygons, each ...
1
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0answers
361 views

Geopandas simplify results in gaps between polygons

The goal is to simplify the geometries of a shapefile containing multipolygons. However, when I use Shapely's simplify in geopandas, the result contains gaps between the polygons. I was hoping that ...
1
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1answer
78 views

“Average” of two lines

I have a dataset of pairs of parallel linear features (railway tracks) and I need to simplify each pair into its central/median line. This could be achieved by computing a skeleton as suggested in ...
2
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0answers
65 views

Generalizing / simplifying multipolygon in PostGIS without missing polygons?

By following the rules from this site, I got the output but some polygons do not come within the simplified polygon. I think the problem is with topology. Is there any solution?
11
votes
3answers
887 views

How to anonymise a gps file?

Imagine you have a GPS trace that you want to make anonymous, in the legal sense. How would you do this? Is snapping to the nearest x distance and stripping out the time enough? Are there ...
24
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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 ...
1
vote
1answer
231 views

PostGIS snap line segment endpoint to closest other line segment

I have a PostGIS table of singlepart line segments that I've run the ST_ChaikinSmoothing function on. Smoothing all of the line segments worked great, but these simplified geometries created small ...
1
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0answers
46 views

Convex boundary of polygon [closed]

Is there any tool that can help me with my problem? I have polygons looking like this : And what I want, is to simplify or gain convex boundary of such polygons. I tried Simplify Polygon in ArcMap, ...
1
vote
2answers
133 views

Reduce complexity of KML file

I have a 6mb KML file I am using with the Leaflet API/Ominvore plugin. It is just a centerline of a long distance trail. What would be the best way to make it smaller? Reduce complexity etc.
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 ...
0
votes
2answers
443 views

QGIS remove useless vertex to simplify polygon

I received a shapefile which is the result of a combination of several polygon. I want to clean and simplify it as there are many useless vertex as you can see on the picture. This is only one feature ...
1
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0answers
49 views

How to remove narrow 'notches' in polygons?

I am currently working on a project where i am doing a union on several feature classes. The union normally creates several polygons which share edges/borders. however after running dissolve on the ...
3
votes
1answer
406 views

Reducing number of points, keeping most recent data within given distance, using QGIS?

I have a HUGE dataset of points that were collected along a route. The data may change daily, and the most recent data is the most important. What I would like to do is take only 1 point from a given ...
2
votes
1answer
155 views

Simplify a circle into square with SF

I want to obtain a square from a circle using simplification function in sf. This is my circle: With this code, I obtain a rhombus plot(st_simplify(st_geometry(sfdf),dTolerance = 1000)) How can I ...
1
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1answer
52 views

Remove small interstices on the edges of a polygone

How can I remove the white interstices on the edges (and interior) of a polygone or polyline, as represented in the first figure below? I want to get smooth and continuous edges, capturing the global ...
1
vote
1answer
657 views

Simplify geometry

Which is the best way to convert a complex multipolygon into simple and "merged" polygon? For example, the red stroked polygon (drawn by hand of course) is the simplified version of the white ...
3
votes
1answer
234 views

How to delete from mutipolygons all but the biggest polygon in QGIS

I have a bit too complex multipolygon set to be used in a web application (thematic map) so I'd like to simplify the structure by removing small islands of areas. I am not an expert on QGIS but so far ...
1
vote
0answers
16 views

What simplifying polygons functions f y = f(x) have ( y union x equal y ) property?

I've looked at GRASS v.generalize manual but they don't say. As far I can tell there's hermit but it's a Smoothing function.
6
votes
1answer
2k views

Smooth, not simplify, lines features in PostGIS

I'm trying to automatically generate paths to place labels on that follow the shape of rivers, 4wd tracks and other very windy lines. At first I thought the st_simplify() function was the answer, but ...
2
votes
1answer
944 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 ...
1
vote
1answer
156 views

Aggregating geometry features on geometry simplification using PostGIS?

PostGIS has ST_Simplify functionality which gets one multiline as input and returns one output multiline where the general shape of lines are retained while eliminating unnecessary detail. Instead of ...
2
votes
0answers
195 views

Building footprint polygon simplification / generalisation

I'm looking for implementations of polygon simplification algorithms that preserve topology and overall rectilinearity. The input data is building footprints which often have squarish protrusions and ...
0
votes
1answer
52 views

Reducing filesize for landslide susceptibility map

I have a large .tif file that I would like to reduce to under 15MB (currently 650MB). The file shows 3 zones of landslide susceptibility (see pic below). I am processing it so that I can upload it to ...
2
votes
0answers
290 views

producing smooth iso polygons from raster surface? [closed]

The objective is to turn a raster surface (double value type) into smooth, visually appealing polygons representing iso-levels. I cannot stress enough that these must be visually attractive. Jaggedy ...
2
votes
3answers
678 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(...
2
votes
1answer
267 views

Simplify Geometries 'NoneType' Error in QGIS

I need to simplify the geometries of a large amount of polygons, yet every time I run the Simplify Geometries tool in QGIS, I get the error message below. 'NoneType' object has no attribute 'type' ...
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 ...
5
votes
1answer
544 views

Simplify a road network to obtain the intersections

In QGIS 2.6.1 in Ubuntu, I want to measure the density of block in this city (FYI my final aim is to measure the TOD level). I have the road network from French national IGN dataset BDTopo. I have ...
0
votes
0answers
68 views

How does the US Census Bureau simplify its Cartographic Boundary Shapefiles?

The US Census Cartographic Boundary Shapefiles are available in 1:500,000 and 1:5,000,000 and 1:20,000,000 resolutions. The boundaries are well-aligned and the data otherwise seemingly clean. How ...
2
votes
0answers
135 views

How to simplify line geometry and preserving topology in Oracle?

I have some polylines in an Oracle database which are topologically connected and I want to simplify these lines based on a tolerance directly in Oracle. I need something like ...
1
vote
0answers
211 views

Query to merge simplified polygons according to the map scale-factor [closed]

I'm trying to construct a view in PostgreSQL that simplify polygons according to the map scale-factor. Basically I was reading this thread http://linfiniti.com/2011/06/scale-dependent-generalization-...
1
vote
1answer
352 views

Geoserver shape simplification performance

So, while wondering about shape simplification in the eternal struggle for optimization, I find out (here on SE) that Geoserver and PostGIS can and will (by default) perform the trick on the fly (see ...
2
votes
2answers
885 views

Simplify polylines by eliminating short lines?

I have a river network, extracted from a DEM. Then I split it to shorter segments. The split adds some points (as shown in figure) too near to each other. I wonder how I should remove those small ...
1
vote
0answers
65 views

Output Error from SimpliPy in QGIS

I am trying to simplify a polygon layer of parliamentary constituencies in Kenya using SimplyPy in QGIS and appear to be getting an erroneous result. The method is working for most of the polygons ...
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 ...
1
vote
2answers
784 views

Simplify a shapefile/GeoJSON polygon without “uncovering” territory?

I've been using Mapshaper to simplify some very complex polygons (boundaries of countries). The goal is to create relatively simple polygons which can be used to determine whether a given lat/lon ...
1
vote
0answers
49 views

Keep synchronization when simplify features from different data source

We have two shapefile data sources: 1 water-riverbank.shp With geometry type of Polygon which stands for the area of water 2water-riverline.shp. With geometry type of LineString which stands for ...
6
votes
3answers
5k views

Simplify geometries but keep them contiguous

I have several detailed contiguous areas. I need to turn each one into KML, but when I do so, the end result is too large (in terms of memory). Using PostGIS I need to simplify these geometries but ...
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") ...
1
vote
0answers
212 views

Is it possible to simplify geometry only for polygons with certain attributes?

I have a map of electoral districts. Urban areas have more densely packed districts whose borders are more important to keep at high resolution. More rural districts have simpler geometries and have ...
3
votes
1answer
293 views

Create Strictly Simple Polygon in PostGIS/Shapely

The clipper lib has an amazing function to create a strictly simple polygon (definition below). Is it possible to do this in simple features (pref postgis or shapely)? A strictly simple polygon is a ...