Questions tagged [generalization]

Process that simplifies the representation of geographical data to produce a map at a certain scale with a defined and readable legend. During the process, the information is globally simplified but stays readable and understandable.

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V.Generalize errors

I am using QGIS version 3.24.1-Tisler. I'm trying to simplify contour lines in a very flat area in Canada. The contour lines in this example are 5 meter lines and they are complex to look at, and when ...
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Simplifying polygon edge while preserving minimum area and width [closed]

I am working with river buffer areas. The area that you see in the first picture is a 100-meter buffer of a polyline (a polyline isn't visible but it is there). I want to simplify the edge in a way, ...
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Lining up boundaries at corner of polygons

I have a polygon layer with the boundary of a lot of zones. The boundary of many of them skips at the intersection where multiple zones come together (shown as in the picture). I am trying to find out ...
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Polygon simplification without intersection in GeoPandas/Shapely

Is there an in-the-can solution for simplifying a boundary that won't intersect the original poly? Something like .convex_hull but with a fillet option possibly? For example, .simplify() produces ...
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Making space between tight line features on different scales in QGIS

In QGIS 3.16 I have a shapefile layer where linear features will often be digitised close to each other. These lines are all features in the same layer. Example when zoomed in: Problem when zooming ...
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Generalise low resolution World Bank boundary data

I'm trying to generalize World Bank Official Boundaries:World Boundaries GeoJSON - Low Resolution from https://datacatalog.worldbank.org/dataset/world-bank-official-boundaries using QGIS 3.18.3, using ...
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How to convert a symbol size in millimeter into that in meter by PyQGIS?

Recently I am trying to use PyQGIS API to help auto-mapping in QGIS, and some symbols' overlapping on a map that is to be printed at a certain scale is not in accordance with cartography principles. ...
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Generalizing line with angle rules in QGIS

I'm looking for an automatic way to generalize/simplify vector lines in QGIS like the following picture : I would like the generalization to include only the angles indicated by the small star on the ...
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Smoothing all the intersection for GPX track points?

I have a.GPX Track file that has too many intersections. I want to smooth out due to all the intersection Currently, I'm trying to figure out a way to smooth out this track file. The intersections are ...
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2 votes
2 answers
166 views

Making tiny objects visible for their location when zooming out

I'm adding small features to QGIS that I need to be in a precise location (trail signs) like so: 1:500 However, when I zoom out, they become invisible: 1:10000 If I switch the sizing to millimetres (...
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7 votes
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Optimizing identification of tree stand boundaries

I am working on a workflow to identify tree stand boundaries. My desired result is the blue lines - I know it will never be like that, but I need it to be as good as possible. My best result is the ...
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How to generalize a country border using QGIS? [closed]

What are the steps for smoothening a country border using QGIS?
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Does QGIS have Generalization toolset like ArcGIS Desktop?

In ArcGIS Desktop there are Generalization tools like: Merge Divided Roads Collapse Road Detail Resolve Road Conflicts Does QGIS have this toolset or is it possible to run these algorithms on QGIS?
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How to smooth interior polygons of one shapefile

I have a shapefile that includes the boundary of a field plus many interior polygons that represent levels of NDVI - we'll say High, Medium, and Low. The larger areas have jagged, irregular edges. ...
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Generalization with GRASS explodes number of polygons that are exported to GeoJSON

I have a shape file containing polygons with 10 geographical districts that together form a city, which I want to generalize without "sliver" artifacts and export to GeoJSON. When running this vector ...
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v.generalize does not affect some boundaries

All in all, I would describe myself as a QGIS (3.12.2) beginner and have now contact with GRASS (7.8.2) for the first time. I want to simplify the boundaries of my polygons considering the topology. ...
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Merging two different accurate polygon layers using QGIS

I'd like to combine two layers of different administrative areas. One layer is more accurate (layer A) than the other one (layer B) in terms of generalization. Is there a prepared QGIS-tool to do this?...
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1 answer
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Simplifying label geometry in QGIS

I have a bunch of linear data (trails) stored in PostGIS and visualized in QGIS for cartographic production. Many trails have switchbacks, and are generally very "weavy", which makes for difficult ...
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Problem when using Simplify Tool in QGIS

I want to simplify district borders. As I got bad results when using polygons I converted those polygons into lines but I still have the same problem that I get new vertexes or corners I don't want. ...
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Mapshaper simplify equivalent in GRASS

I was shown the simplify function of https://mapshaper.org/, which removes unnecessary vertices in polygons. Now I'm looking for a similar function in QGIS and found GRASS generalisation. Since I'm ...
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How to simplify and generalise global data for cartography?

I have a TIFF that shows biodiversity and I want to create a nicely looking cartography output. The data look like this If you can observe there are a lot of 'dots' and things can get a bit messy ...
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3 votes
3 answers
148 views

Generalising lines of varying detail in QGIS

I am trying to generalise a line in QGIS so that I can export it as a vector without it having an unnecessarily huge file size. The line shows the GPS track of a road trip, and as such varies between ...
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202 views

Generalizing railways from OpenStreetMap using ArcGIS Desktop?

I have dataset of railways from OpenStreetMap. It is really detailed. But i want to make generalization for map scale 1:500 000: remove small details of the railways and short branches. I`ve used ...
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4 votes
2 answers
463 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 ...
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4 votes
3 answers
2k views

Automatically fill gaps and merge freshly generated polygons with the longest adjacent polygon

I get polylines automatically generated from AutoCAD from a colleague. Converting them into polygons with QGIS 3.6, I find out some sliver polygons and gaps in between, as shown in the picture below : ...
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171 views

Simplify a polyline/polygon using a threshold on maximum number of vertices in PostGIS?

The various simplification functions in PostGIS (e.g. ST_Simplify) uses a tolerance parameter for the maximum allowable deviation of the generalized shape from the original. My question is: Is there ...
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253 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?
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"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 ...
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2 votes
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Conditional Expanding in ArcGIS Desktop?

I would like to reclassify a LC map given some conditional rules (raster with 8 classes total). Using the illustration, I would like to expand the green pixels (two distinct classes) on the white ...
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1 vote
1 answer
465 views

v.generalize in QGIS throwing "Unable to create table" error

I am trying to smoothen few polyline shapefiles using v.generalize in QGIS 3.4. But it's not working. Even i tried the same in QGIS 2.18. Getting the same error. Tried the same process in GRASS 7.4.2....
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5 votes
3 answers
1k 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 ...
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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, ...
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64 views

How to remove complicated shapes in ArcGIS - generalization [duplicate]

What can be the way of simplifying polygons in ArcMap? I have a shapefile with buildings and I have to make them as simple as it's possible. I used already some tools, like: dissolve, union, ...
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1 answer
270 views

Avoiding thin parts of polygons using ArcGIS Desktop?

I've used Simplify Polygon with 'Maximum Allowable Offset' 250m, and then Aggregate Polygons with 'Aggregation Distance' also 250m (opposite order also tested). Still I have thin parts of polygons as ...
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5 votes
1 answer
134 views

Getting WHERE statement to work in v.generalize?

I have a shape (its topology is terrible but I don't think it's the problem). I'm trying to simplify it to reduced it's size using v.generalise. I succeeded at reducing the whole shape but I ...
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3 votes
1 answer
464 views

Display multiple lines as one line in QGIS

I am working with the OSM Dataset and can´t find a way to display rails in a proper way. In a big scale the rails are displaying fine but as soon the lines begin to overlap in a smaller scale I don´t ...
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3 votes
1 answer
88 views

Is there a built in way to reduce the amount of points in an IElement

I have a polyline element and I want to reduce the number of points (vertices?) that make up the line. I know it will make the curved sections jagged and that is fine. I just want to control (perhaps ...
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3 votes
2 answers
916 views

Dissolving "neighbour"/bordering polygon features in QGIS

I have a polygon layer with buildings for the area of the whole city. My question is how to dissolve/aggregate/merge only those buildings, that are "neighbours", in a sense that they share ...
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2 votes
0 answers
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How to generalize shape with PyQGIS without much Distortion in the shape?

I was trying to generalize the the inner boundaries of the polygon. Looking for a PyQGIS solution for that any other possible python solution will be fine. I tried convex hull and simplify geometry ...
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2 votes
0 answers
35 views

Smooth Data Values Across Geographies with Zero Population

Looking to fill in gaps through generalizing a population count across U.S. counties. I.e., if a county has 0 population, but is surrounded by 5 non-zero counties, then change the 0-population county ...
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1 vote
1 answer
75 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 ...
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1 vote
0 answers
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Generalize Polygons in QGIS 3.0

I would like to use different generalization tools for polygons in QGIS 3.0. Especially for aggregation, simplifying and smoothing. Back using QGIS 2.8 there were the following possibilities: ...
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3 votes
2 answers
192 views

How to generalize QGIS 3.0 Model so that I can install on multiple computers without setting up on every computer?

I am trying to create a model to work on multiple computers with little editing. I am working in QGIS 3.0. I am trying to get the model to first set the style for the layers based on a predefined qlr. ...
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1 vote
0 answers
121 views

Speeding up workflow of generalizing OpenStreetMap road data?

Whenever I want to use OSM data for medium scale maps (e.g. 1:200.000) I run into problems. On the screenshot below one can see the orange street that goes from north to south. It has the attribut ...
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2 votes
0 answers
365 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 ...
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0 votes
1 answer
58 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 ...
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1 vote
1 answer
2k views

Merging unconnected line segments using ArcGIS Desktop?

I am looking for a way to connect line segments that are unconnected. It is a shapefile for a network of rivers and all the lines are slightly disconnected. Is there something like aggregate ...
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2 votes
0 answers
432 views

Reducing the density of points based on zoom level

I have a Polyline like the one shown in the example, representing the path of a vehicle. GeoJSON markers show the vehicle's position over time. How can I reduce the density of the markers when the ...
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1 vote
1 answer
156 views

Options for generalizing raster?

I have a DTM raster which has too high a spatial resolution for my intended use, and I need it more generalized. Can't put my finger on how much more, but considerably more. My first thought was to ...
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1 vote
1 answer
385 views

Generalising Rasters using .ovr pyramid data?

I have to produce some lower spatial resolution rasters from a large number of very big geotiffs (c.800GB). It occured to me that since I've produced the pyramid overviews using GDAL already I could ...
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