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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46
votes
5answers
36k views

What raster smoothing/generalization tools are available?

I have a DEM that I would like to smooth or generalize to remove topographic extremes (chop off peaks and fill-in valleys). Ideally, I would also like to have control over the radius or level of "...
42
votes
5answers
62k views

Smoothing/generalizing polygon in QGIS?

Is it possible to smooth or generalize a polygon in QGIS, perhaps by using a plugin like the generalizer-plugin for lines? I could convert my polygons to lines, smooth them and convert them back to ...
36
votes
5answers
8k views

Generalizing polygon file while maintaining topology in QGIS?

I have a polygon Shapefile, which I need to generalize. How can I generalize the poligons and ensure that there are no topological errors like "slivers". I already tried: Vector -> Geometry Tools -...
25
votes
10answers
7k 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 ...
24
votes
5answers
5k views

Rendering overlapping lines

I am making a map containing information about public transportation: busses, trams, etc. The map will have a layer containing for example the tram lines. Each line has its own colour, and is ...
23
votes
5answers
2k views

Simplifying geometries (generalization)

What are the recommended ways of simplifying geometries? Keeping in mind projections, and simplifying state geometries for example. I've heard about converting to an 'equi-distant' projection that ...
22
votes
3answers
11k views

Performing Raster Noise Reduction and Edge Smoothing?

I have a raster image like this I want to delete the isolated noise point and smooth the edge (say the white single points, and I want the edges of the entity look smooth). How can I do this in ...
22
votes
3answers
14k views

Seeking Generalisation Strategies for Building Outlines in PostGIS?

I have a dataset of building footprints vectorised from a raster dataset. The dataset is currently just a vector representation of the raster data. I would like a polygon dataset that only has ...
18
votes
3answers
3k views

How to generalize SpatialPolygons and conserving topology in R?

I would like to generalize a SpatialPolygonsDataFrame in R to make plotting more efficient. The polygons I have result in huge pdf plots that are slow to load and hard to integrate into a document. ...
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 ...
14
votes
1answer
2k views

Using “Merge Divided Roads” tool with lesser parallel lines

When using the "Merge Divided Roads" tool, it merges roads that "trend generally parallel to one another". This means that from figure one.. It will merge the beginning, where the roads are close to ...
12
votes
2answers
6k views

Raster generalization - buffers in rasters, expand pixels?

Is it possible to create buffers for pixels of raster files? Actually I need to expand the pixels classified as 1 (in white in the figure) with a spatial range of 1 or 2 pixels, in order to perform ...
12
votes
4answers
721 views

How to generalize coastlines?

I have a large set of data points that essentially represent the coastline of the world. I don't know the exact resolution but I'd say it's in the neighbourhood of 5-10m. Imagine a set of points ...
10
votes
4answers
6k views

How to generalize a point feature class

I have a point featureclass with a point for every 25cm - in Total 400,000 Points. I would like to reduce this resolution to one point every Meter. How could I instruct ArcGIS Advanced(ArcInfo) to do ...
10
votes
2answers
2k views

Combining high resolution and generalized hillshade rasters to produce enhanced shaded relief?

I often add LiDAR data to a map along with a shaded relief. Most of the time I have to generalize the LiDAR DEM depending on the scale of the map. Still, there is often too much detail and mountain ...
9
votes
3answers
215 views

Understanding location storage and query algorithms?

One of the most important aspects of a GIS-equipped database is that it provides the user with the capability to quickly query for all points within some arbitrary geographic area that match some ...
9
votes
1answer
931 views

Why does GRASS eliminate polygons when using v.generalize?

I am facing a dilemma while trying to use v.generalize to simplify polygons which are similar in size and structure to US Counties or States. Often, I lose polygons from the data set after running ...
8
votes
3answers
821 views

Why are the holes in my polygons not generalized?

I have one polygon layer with many holes. I would like to generalize it. I used v.generalize of grass. With it, I used chaiken algorithm. But, only the borders of polygons were generalized, the holes ...
8
votes
3answers
4k views

QGIS equivalent to ArcGIS Aggregate Polygons?

I am looking for a tool in QGIS 2.40 that performs the function ArcGIS refers to as Aggregate Polygons. Basically it takes a group of polygons within a specified distance and creates a concave hull ...
8
votes
3answers
2k views

Retrieve polygon smallest MBR

I have a postgis table containing polygons. I want to transform my polygons to 4 points polygons : retrieve the smallest MBR. Here comes an illustration of what I want : My original polygon is in ...
8
votes
1answer
235 views

What do you call this non-hole edge condition?

After generalizing or simplifying polygons, you often get legitimate holes in polygons, which are separate parts and can be filled. But what is the correct term for this triangular shape? It is an ...
7
votes
6answers
2k views

Tool/Algorithm for generalizing OSM-Files for printing maps

Is there a tool or algorithm to (topological) generalizes OSM-shapes? I would like to build a printable map in different scales. In the image below you can see the same divided road (yellow) at ...
7
votes
2answers
1k views

Using ArcGIS to filter cells where 7 or 8 of neighbors are different

I have land cover data that I would like to clean using some generalization tools. Majority filter does almost exactly what I want, but is missing one key option. Majority filter allows you to change ...
7
votes
1answer
126 views

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 ...
7
votes
2answers
6k views

Tips for minimizing shapefile size without compromising geographical detail?

I work for a state government's fisheries service, and lately we've been digitizing a lot of our regulatory boundaries within the state's waters that we'd like to service out on web maps. ...
7
votes
0answers
174 views

Alternative to Delete Polygons And Extend Lines of Production Mapping? [closed]

Maybe someone knows an alternative for the Delete Polygons And Extend Lines (Production Mapping) tool or a simple way to achieve the same result but without requiring a Production Mapping license?
6
votes
1answer
109 views

Dividing the world space to geographic sub-space

I am trying to divide the world space to geographic sub-space from "general" to "specific" locations and without using latitude and longitude information. That is, I am trying to think about the world ...
6
votes
1answer
481 views

Raster aggregation in ArcGIS Desktop?

I'd like to aggregate a raster from 1m to 6m in ArcGIS with a custom rule. For example, each cell value of aggregated raster = mean value of 5 highest cell values from 36 aggregated values. How do ...
6
votes
1answer
667 views

How to cartographically generalise buildings/settlements in QGIS?

I have a set of buildings in a polygon layer which I'm going to use in a 50k map. Since the buildings are tiny I cannot show the actual form of the building, instead I'm taking the centroid of the ...
6
votes
1answer
1k views

Competing approaches to line & polygon simplification

There seems to be a few theoretical options around at the moment for geometric simplification. Douglas–Peucker seems the most established, followed by Visvalingam's approach (used by d3.js). Now ...
6
votes
1answer
196 views

Finding Ring Smaller than a certain tolerance

In Simplifying a shapefile for world timezones http://efele.net/maps/tz/world/ all generalize/simplify algorithms fail on 5 countries/states, shown in this shape file http://enclick.com/...
6
votes
0answers
345 views

GeoServer pregeneralized layers not working as expected [closed]

I've set up GeoServer 2.1.4 and installed the feature-pregeneralized-2.1.4.jar plug in and processed my shape files into each of their separate folders with the generalized shapefiles and I've check ...
5
votes
2answers
13k 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 ...
5
votes
2answers
4k views

Merge point features within a given radius [duplicate]

I have a file in QGIS with 5000 points. Some of the points are really close to each other (5m). How can I cluster the point features to one point feature if they are within 5m? The new points should ...
5
votes
5answers
2k views

Aggregating detached polygons using open source software

Is there any open-source library to aggregate detached polygons? I know that there is a tool in ArcInfo, but it is commercial.
5
votes
1answer
2k views

How to reproduce Smoothing from Generalizer Plugin in v.generalizer in Processing Toolbar using QGIS?

I´d like to reproduce the smoothing operations done with the Generalizer Plugin inside the v.generalizer Toolbox so I can use them on a polygon layer instead of only on a line layer. I tried ...
5
votes
2answers
2k views

Tracklogs to single line OR several lines to one line?

Setting: I have several trucks driving out of my factory delivering goods and coming back for more deliveries. These trucks are equipped with GPS so that they may return tracklogs to me. These ...
5
votes
1answer
102 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 ...
5
votes
2answers
540 views

how to get a low level road network from openstreetmap data?

I've extracted the road network of a city from openstreetmaps (filetype: osm). One part of the road networks look like this: However, there are too many details in this data. I'd like to represent ...
4
votes
2answers
1k views

Removing unnecessary vertices at places with no change of direction?

I am aware that this question has been asked here: Removing unnecessary vertices?. I want to focus a different point. How to remove unnecessary vertices without changing the shape at all. As you can ...
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 ...
4
votes
3answers
350 views

Enlarge/roughen the Vector Size of Tiles

I'm currently running a GeoServer service and my task is to make the vectors rougher than they are right now. I really don't know where and how GeoServer processes the data from the database and how ...
4
votes
1answer
2k views

How to maintain right-angles when buffering?

When buffering some polygons I am trying to avoid the curved buffered area like this: I'm trying to do thins within an FME workbench but if someone knows how its done in other software that would ...
4
votes
1answer
926 views

Flatten GIS data to a schematic

I want to take a network of roads and lanes and reduce them to a schematic that shows their relationships but not their geographic shape. A similar concept has been used for the London Underground ...
4
votes
0answers
48 views

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 ...
3
votes
3answers
83 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 ...
3
votes
1answer
53 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 ...
3
votes
2answers
424 views

Need an explanation on a network simplification algorithm

I try to implement the algorithm described in this paper (page 8), but there's a place that I can't understand, and the authors do not provide a more detailed explanation or pseudocode. They show how ...
3
votes
1answer
580 views

Is it possible to simplify orthogonal polygons with OpenCarto Java Library?

I want to know if simplification of orthogonal polygons can be done with OpenCarto Java Library. If yes, does it have any API documentation?