# Tagged Questions

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.

3answers
817 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 ...
1answer
485 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?
0answers
37 views

### Gdal ogr simplify/intersects

Can anyone give an example: How to use the simplification? For example // read the coordinates of the polygon char * wgsRef = NULL; OGRPolygon *poPol = (OGRPolygon *)...
0answers
39 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 ...
5answers
3k 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 ...
0answers
42 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 ...
0answers
26 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 ...
2answers
2k 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 ...
1answer
54 views

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

I came across How to generalize a polygon file and maintain 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 (...
1answer
86 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 ...
10answers
4k 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 ...
0answers
29 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 ...
0answers
49 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 ...
1answer
460 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 ...
2answers
90 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 ...
2answers
35 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 ...
1answer
47 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 ...
0answers
26 views

### Can GeoServer be asked to clip a WFS response?

I'm fairly new to GIS, so I'm not very familiar with all the terminology and standards. What I need is a webservice that returns geographical polygons (countries and administrative regions) as GeoJSON....
1answer
232 views

### QGIS 2.6 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 ...
1answer
60 views

### Simplify shape files [closed]

I've shape files 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.
2answers
209 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 ...
1answer
1k 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 ...
0answers
54 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 ...
0answers
38 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 ...
1answer
67 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 ...
1answer
125 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 ...
1answer
35 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) ...
0answers
238 views

### How do I simplify the straight sections of (multi)Linestring in PostGres/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 ...
0answers
47 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 ...
2answers
188 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 ...
2answers
110 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....
2answers
58 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 ...
1answer
70 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 ...
0answers
91 views

### Query to merge simplified polygons according to the map scale-factor

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-...
0answers
46 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 ...
1answer
76 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 ...
2answers
416 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, ...
1answer
549 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 ...
1answer
198 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 ...
1answer
93 views

### simplify tiled geometries while preserving anything on the edge

I have a dataset of polygons split into evenly sized tiles. How can I go about simplifying them, but not along the tile edges, so that there aren't any gaps between continuous features when the tiles ...
1answer
144 views

### What is the best way to get 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. ...
2answers
524 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 ...
2answers
151 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 (...
1answer
678 views

### How Does Ogr2Ogr Simplify Work?

Can someone explain how the ogr2ogr simplify works? I am trying to use raster data which has a spectral resolution of 30m. The vector file that I am trying to import into Google Fusion is large in ...
1answer
401 views

### Collapse multiple lines into a single line

I need to create a route (line) feature class from another feature class that contains multiple lines making up the same route. pic 1 shows the original feature class with the multiple lines. pic ...
1answer
139 views

### Reduce number of points, keeping most recent data within a given distance

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 ...
1answer
116 views

### Simplifying polygons in ArcGIS considering contains-one-point topology rule?

I want to simplify polygons using the "Simplify Polygon (Cartography)" tool in ArcGIS 10.2. Additionaly there is one point in each polygon and this condition should still be fulfilled after ...
4answers
585 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 ...
2answers
2k 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 ...
1answer
242 views

### Simplify a polygon dataset with a minimum distance between the new vertices

I would like to simplify a polygon shapefile where the resulting output has a minimum distance of 5 kilometres between the new vertices. We have ArcMap 10 on an ArcView license, FME and QGIS. I have ...