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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.

32 questions with no upvoted or accepted answers
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11
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1answer
746 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 ...
6
votes
0answers
780 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 ...
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 ...
2
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0answers
54 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 ...
2
votes
0answers
64 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?
2
votes
0answers
194 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 ...
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 ...
2
votes
0answers
321 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
1k 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
293 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 ...
2
votes
0answers
123 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 ...
2
votes
0answers
134 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 ...
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 ...
1
vote
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] ,[...
1
vote
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
vote
0answers
353 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
vote
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 ...
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.
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 ...
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 ...
1
vote
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
vote
0answers
124 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 ...
1
vote
0answers
646 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/...
1
vote
0answers
380 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 ...
1
vote
0answers
753 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 ...
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
0answers
108 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 ...
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 ...
1
vote
0answers
48 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 ...
0
votes
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 ...
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 ...
0
votes
0answers
192 views

Reducing point numbers in a certain area

We have a list of poi data in our database(Access mdb db), and we have a web service which serve data by a specified BoundingBox. However we found that the returned points are too close to another at ...