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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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") ...
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0answers
213 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
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1answer
295 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 ...
2
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1answer
167 views

How do I remove only coastlines in marine shapefiles and be left with only polylines in the ocean?

I have numerous marine shapefiles that need to be simplified for display purposes. I need to eliminate the coastlines of land entirely and be left with just polylines in the ocean, as the Large ...
3
votes
1answer
249 views

Methods behind qgis:simplifygeometries and qgis:smoothgeometry?

I would like to know on which method (e.g. Douglas-Peucker line simplification) the modules qgis:simplifygeometries and qgis:smoothgeometry are built on. I cannot find further information on these ...
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0answers
30 views

Exact method used in simplify command within “Convert ArcGIS Raster to Polygons”

I am trying to understand the exact method used in the "simplify" command under the "Convert Raster to Polygons" in ArcGIS. The help page describes qualitatively what the command does, but does not ...
1
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0answers
126 views

Simplifying polygons without “trimming” them

I have a quite difficult issue: I need to simplify polygons, but without "trimming" them - no parts of polygon can be lost; furthermore, all holes in polygons should be filled (but this last is less ...
2
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0answers
327 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
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1answer
2k views

How to use OGR Simplify in Python

I am trying to simplify several polygons part of one shapefile using Python and OGR. However, I am stuck with how to use the simplify function as mentioned in the documentation: http://www.gdal.org/...
2
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1answer
3k views

Advanced Digitizing Error CAD tools are not enabled for the current map layer

Using QGIS 2.8.4. I want to use the Simplify function so turn on the Advanced Digitizing menu. The panel displays an error "CAD tools are not enabled for the current map layer" and the error message ...
-4
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1answer
237 views

Simplify shapefiles [closed]

I've shapefiles with me and I want to de-code those file and want to build a custom map. Could someone let me know how can I do that with out using Python code.
3
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1answer
159 views

qgis: generalisation & covex - how to? what plugin?

I'm looking for a way to generalize and simlify polygon to remove "internal spikes" as ilustrated below. The violet in input and green expected poligon.
1
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0answers
658 views

Postgis : Simplify a path using ST_Simplify

I have a table with latitude, longitude representing paths. I want to simplify the paths using Postgis ST_Simplify Here is a sample set of 89 GPS points i try to simplify : https://gist.github.com/...
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 ...
1
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0answers
384 views

Simplifying boundaries of divisions of country using QGIS?

I am trying to create a map to show all the divisions of a country (regions, departments), but the original map (one SHP file), with a lot of detail in the boundaries, is 5-Mb sized. I'd like to ...
4
votes
2answers
12k 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 ...
1
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0answers
52 views

Simplify geometry of multiple features without losing shape [duplicate]

I am simplifying administrative boundaries using a high simplify tolerance (which is my intention so as to get a minimalist appearance). However, after simplification, the borders of the regions no ...
7
votes
2answers
508 views

Complex Shapefile Compression Advice

I'm looking for some advice on how I can simplify this very detailed shapefile to ultimately be used for the web (as topojson) as a interactive heatmap. It was originally created from a raster file (...
3
votes
1answer
420 views

How to use GRASS Generalize to reduce GADM data size to 1/5 preserving topology?

The GADM is a great resource from global boundaries of countries, states and municipalities. The amount of detail is suitable for many analyses but when it comes to mapping or displaying it is often ...
6
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1answer
2k views

How do I smooth edges of polygons in QGIS?

Is there a built in function or plugin I can use to achieve smooth lines for my polygons instead of the blocky ones I have now?
0
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3answers
543 views

Simplifying Ways in OpenStreetMap Data

Is there a (current) best practice to simplify ways? I have found: https://github.com/podolsir/osmosis-simplifyways But besides not being alive, here (http://permalink.gmane.org/gmane.comp.gis....
1
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1answer
496 views

Simplify networks from OSM in qgis

I want to make something like in this question in QGIS. In ArcGIS there is available Make Divided Roads plugin. Is there easy way to make the same job in QGIS?
0
votes
1answer
215 views

Getting simplified UK boundary data?

I have some recent data that is at the Lower Super Output Area (LSOA) level for Greater Manchester. I wrongly assumed that the data was for the latest LSOA boundaries, i.e. for the 2011 boundaries. ...
16
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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 ...
4
votes
1answer
191 views

How to delete vertices with the same direction

I have feature with a big amount of vertices. But these vertices are totally useless and make Qgis editing too slow. Lets look on image with example: These vertices inside of black line I want to ...
8
votes
3answers
2k views

Lossless Polygon Simplification?

Is there a standard/recommended algorithm for simplifying a polygon without shrinking any of its original boundaries? Right now I'm using TopologyPreservingSimplifer within JTS and running into ...
2
votes
0answers
2k views

Algorithm to simplify a Polygon/Series of Points to a given number of Points

I have a polygon (or let's call it just a series of points). I want to simplify it (reduce the amount of points) to a given number of points. Currently I use Douglas Peucker and try to guess the ...
2
votes
0answers
294 views

Filtering Small Areas of Shapefiles Using R

I'm trying to use the method proposed by the @ialm in the Question "How to speed up the plotting of polygons in R?" There, he loads the maps using getData from the raster package, I tested and it ...
1
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0answers
765 views

How to calculate tolerance for TopologyPreservingSimplifier in JTS?

I am trying to simplify some areal geometries (POLYGON\MULTIPOLYGON) using JTS's TopologyPreservingSimplifier.simplify(Geometry geom, double distanceTolerance) From the JavaDoc: void ...
2
votes
1answer
538 views

Generalizing (simplifying) polygon shapefile or feature class in ArcMap while preserving topology?

I came across Generalizing polygon file while maintaining topology in QGIS? which asks for a QGIS solution to my exact question. I'm trying to do this in ArcMap. I start with a polygon shapefile (...
2
votes
1answer
776 views

Using Chaiken Method parameters for smoothing polygon vectors in QGIS [duplicate]

I've been trying to smooth a huge polygon, that is result of a segmentation export. I'd like to know what's the best parameters to use Chaiken Method to get smooth curved boundaries on QGIS 2.14. I ...
1
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0answers
118 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 ...
6
votes
0answers
784 views

ogr2ogr (or other) simplification of polygons with shared boundaries

I am trying to simplify a collection of 100,000 or so polygons containing nearly 4 million vertices. The data is stored in a 2GB shapefile so there is no explicit representation of the topology ...
5
votes
1answer
1k views

ogr SimplifyPreserveTopology does not keep the Topology

I use ogr2ogr to simplify a layer of polyline, from the document: -simplify tolerance: (starting with GDAL 1.9.0) distance tolerance for simplification. This method will preserve topology, in ...
5
votes
2answers
70 views

How to find fluctuant parts in a trajectory

I am currently doing an assignment on how to compress a trajectory. Given a trajectory T1 in figure 1, and I want to get a compressed version as T2. For segments p0~p3 and p6~p9 in T2, I can obtain ...
1
vote
1answer
621 views

Can I simplify geometry on the fly in a ArcGIS JavaScript map viewer?

We've got a polygon feature class of parcels around a lake boundary that is incredibly accurate. The editor did a really thorough job of following all the inlets and meanders along the edge. From just ...
4
votes
2answers
2k views

Simplify/generalize Polygons and keep topology of different layers PostGIS/QGIS

i have some polygons of a country, states, districts, communities and i want to simplify the geometry. i already simplified the geometry of each layer but afterwards of course it doesnt fit with the ...
4
votes
1answer
2k views

Changing the scale (generalisation) in ArcGIS 10

I have 2 polygon layers, accordingly 1:10 000 and 1:500 000. I want to generalize the first layer from 1:10 000 to 1:500 000. I tried using Simplify polygon tool, and since these scales relate to ...
1
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0answers
109 views

Resolve Building Conflicts - the open source way?

In ArcGIS there is a tool called Resolve Building Conflicts and I'd like to achieve the same using only open source tools (QGIS, GDAL etc), preferably on Mac OS instead. In the long run I'm trying to ...
2
votes
0answers
124 views

C/C++ function to return minimum set of points required to represent a geometric shape

I am looking for a method from Grass, GEOS, or similar that will delete those points in a geometry which do not affect its shape. Example 1 +----+----+ p0 p1 p2 p1 can be deleted without ...
3
votes
1answer
115 views

Generalizing exact location of certain data points using Carto CSS?

I am dealing with some sensitive data for which providing a high resolution of accuracy of the location would be detrimental. However, the general location is not sensitive and useful to share. I ...
2
votes
1answer
335 views

PostGIS: How to dissolve vector data

I have a few scenarios where I need to dissolve vector data, and I'm wondering how to do this using PostGIS. What would the queries look like to perform these operations? Below I'll describe the ...
2
votes
1answer
116 views

QGIS simplify geometries shifts polygons north

I'm trying to simplify polygons in a shapefile using the "Simplify Geometries" tool in QGIS 2.10 (Pisa). This works as expected, except for one strange effect: the resulting features (shown in green) ...
2
votes
0answers
135 views

Combine files in TopoJSON when one is simplified differently to the other

I have two .shp files, I am separately converting these to GeoJSON with ogr2ogr.exe and then combining the files with TopoJSON. Each file independently becomes a ~200kb topojson file, however the ...
1
vote
2answers
187 views

Cannot Select 'Input line or polygon vector layer' when trying to simplify Shapefile

I'm trying to simplify a Shapefile by opening it in QGIS, Go to the Vector menu, selecting Geometry tools, and selecting Simplify Geometries... When I do this I get a modal window that I can fill out ...
6
votes
1answer
301 views

Is there a difference in results between Simplifying a geometry by different projections?

We have geometries in a PostGIS database projected in srid 4326. We need to have these geometries simplified with ST_SimplifyPreserveTopology. My question is whether this geometry needs to be ...
1
vote
0answers
53 views

QGIS - Simplification process creates a new polygon - how to avoid it?

I am trying to simplify a layer made of polygons. I have used different methods but the new simplified layer has a polygon which intersect with itself, thus creating a "new" polygon. Please see ...
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, ...
5
votes
1answer
619 views

Simplifying polygons made from binary rasters using ArcGIS Spatial Analyst?

I'm using MaxEnt to produce a species presence / absence raster layer. It works fine but I have to choose a cut off point for what constitutes presence or absence. As a result I end up with a lot of ...
2
votes
1answer
335 views

How to fill a hole - with islands within?

In QGIS I have simplified a layer. At the end of the simplification process (using GRASS v.generalize), my final layer "lost" a polygon: see white space in image: How can I recreate a polygon which ...