Questions tagged [polygon]

On a map, a closed shape defined by a connected sequence of x,y coordinate pairs, where the first and last coordinate pair are the same and all other pairs are unique.

451 questions with no upvoted or accepted answers
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1answer
863 views

Merge adjacent polygons and return all (adjacent and not adjacent) as Multipolygon?

I have a postgres database with administrative boundaries and their geometry. Each of those boundaries have an ident number. What I want to achieve: First I want to select all rows which are ...
6
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2answers
614 views

Creating voronoi polygons from polygons?

I have a database with buildings and for some further analysis I need to: aggregate adjacent buildings (preferably without losing the height attribute, but I can work my way around that) once I have ...
5
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0answers
725 views

What is the best way to display a large shapefile (with polygons) as a layer on a leaflet map?

I have a leaflet map of the UK with around ~2000 points total points and a bit of metadata loading for each point with two side-panels showing the metadata. These points are drawn from several tables ...
4
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0answers
37 views

Randomized organic warp of adjacent polygons that preserves topology and fixed nodes

I'm looking for algoritms to modify a set of polygons to make them appear more organic. They still need to maintain their topology and furthermore some of the nodes might be fixed. Please see the ...
4
votes
1answer
148 views

Use DEM elevation attributes in vector polygon?

I am modeling glacier retreat scatching polygons on DEM surface trying to come out with 3D scatch. Is it possible to adjust "height" of polygon to follow elevation of DEM surface (eg. glacier height ...
4
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0answers
70 views

Creating Raster that sums up input polygons using QGIS?

I am using QGIS and I have a shapefile with buildings. From these buildings, I have built Buffer with variegating radius. The Buffer also have data about the demand for Parking spots for each building....
4
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0answers
853 views

Fastest way to union a set of polygons in R

I want to find the fastest way to union a set of polygons into one large polygon. Lets first get some data: # Load libraries library('raster') library('geosphere') library('mapview') library(...
4
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0answers
290 views

QGIS Zonal Statistics for polygons is missing results?

I am carrying out an analysis using QGIS 2.14.1 where I am dealing with point data that have been randomly displaced by either up to 2 Km or 5 Km. I have generated a buffer of the appropriate radius ...
4
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0answers
364 views

How to create text buffer in the legend- QGIS 2.18?

I work with this polygon layer and this is my map composer: I used the labels with Text Buffer (yellow and red), and I try to find how I can make the same text buffer in the layer name in the legend. ...
4
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0answers
511 views

Clip of polygons does not work properly by invalid geometry

I want to clip a polygon shapefile by another polygon shapefile. Input polygon is the green one (first), clip polygon is the light blue one (second) and the result should look like the dark blue one (...
4
votes
0answers
986 views

Find Distance Between Two Polygons

Given two polygons (point, line, or up to 8 vertices) I need to be able to calculate the shortest distance between them via code I write or a call to an API (I haven't been able to find one that does ...
4
votes
0answers
219 views

Reshaping polygons while preserving area

I'm looking to manually skew the shapes of areal polygons, but need to ensure their areas are not altered. Is anyone aware of any GIS tools or programming workflows that exist for manually reshaping ...
3
votes
3answers
161 views

How to remove narrow polygon dangles

Using QGIS v 3.4.4. I have a polygon layer in which some shapes have a very narrow extension that i would like to remove. Unless zoomed in these extensions appear as dangles but when zoomed right in ...
3
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0answers
66 views

Creating equidistant sampling points in polygon in QGIS 3.6.0?

I have figured out how to add random points inside polygon boundaries. Although this works well, nevertheless I need a few different things to happen for my application. What I would like to do is ...
3
votes
0answers
77 views

Unable to compute intersection between two polygons using PyQGIS?

I have two polygons in different layers. I am trying to find the intersect between the two polygons. Below a figure showing my test case. I initially wanted to find the intersect between the green ...
3
votes
1answer
352 views

How do I split polygon in equal parts based on polygon area?

So, I came across this relevant question, but I think my problem is a bit different. I have two tables i.e. polygon poly and points pts in my Postgres db. I am on Windows 10 (x64) based machine and ...
3
votes
0answers
92 views

Expanding polygons and clipping at midpoint?

I have several separate shapefiles with polygon features. The end goal is to maintain separate shapefiles for each polygon but form a contiguous, non-overlapping coverage for my area. Basically, I ...
3
votes
0answers
51 views

Dynamic filtering based on selected Layer in ArcGIS Desktop?

I am not sure this is even possible, I have about 38 geographical polygon layers showing areas of the UK, I also have a query (point layer) that shows all of the offices around the uk. What I am ...
3
votes
0answers
131 views

Why do I get invalid elements (polygons), when smoothing a vector layer (smooth geometry)?

The problem occurs, when using the commands "Smooth geometry" or "v.generalize.smooth" in QGIS. The shapefile, which I want to smooth, shows a flood water level and looks like this: The water level ...
3
votes
0answers
481 views

Near Tool in QGIS

I am looking for an equivalent to the Near- Tool from ArcMap in QGIS. I have a Polygon Layer with potential areas for a new school and need to calculate the distance (in meters) to a point layer (with ...
3
votes
0answers
72 views

Constructing contiguous regions with similar properties by graph partitioning

I have census data for census output areas. Each area is a geographical region. I would like to partition these areas into contiguous super-regions with similar properties. For example, in each area ...
3
votes
0answers
67 views

QGIS - Layer missing polygons after pointsfile transformation

I'm using pointsfile transformation in QGIS for the georeferentiation of my layers. After the transformation the result some times has polygons missing like here: Why is this happening? How do I ...
3
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0answers
637 views

Troubleshoot with “Split selected features with selected line from another layer”

I am trying to use the "Split selected features with selected line from another layer" tool from the plugin Digitizing Tools in QGIS. Sometimes, this tool works with my shapefiles but sometimes it ...
3
votes
1answer
596 views

Using Check Geometries plugin for polygons in QGIS?

I've a few hundred polygon features with many duplicate nodes, gaps, overlaps and other geometry errors. Fixing all errors seems to be quite tricky. I had to run the duplicate nodes check twice to fix ...
3
votes
0answers
166 views

Can I reorder the points in a GEOS LineString?

Using libgeos, when I buffer() a polygon and then getExteriorRing() [to make a slightly smaller outline copy of the polygon just inside the original], it seems that which point on the new geometry is ...
3
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0answers
49 views

How do you show agreement between polygons based on hand-drawn maps?

I'm somewhat new to GIS, coming from a linguistic background, and now I'm trying to make QGIS do something that I want from that background. I have some hand drawn maps with certain areas of the ...
3
votes
0answers
121 views

Shaded KML overlays on OSM tiles in QGIS?

This seems simple - but the solution is escaping me. I have a series of dynamically generated KML files describing simple, shaded polygons, with each polygon having a slightly different (externally ...
3
votes
0answers
174 views

Adjacency matrix for polygons using Java

I am trying to create an adjacency matrix from a set of polygons. That is, I have a bunch of polygons and I want to identify which polygons have a common edge or "touch" each other. Once I find this ...
3
votes
0answers
242 views

Create polygons from many small. Expand to include space between

I'm just a programmer without GIS-skills as such. Hence this question: Intro: I have a lot of polygons; actually each private-owned real estate in my country. I also have "counties" as polygons. In ...
3
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0answers
543 views

Polygon Layer Cleaning with QGIS

I have a little situation with my data. I have vectorized a raster layer, and now I have some issues with the geometries, as you can see in the picture. Most of errors I have are like this one. ...
3
votes
0answers
325 views

Why do each of my buffer-polygons have different areas

I`m using Qgis 2.2 and 2.4 and loaded a wms-map using the coordinate system ERTS89 UTM 32N. I set 8 points (all in on shp-fileand in UTM 32N) on various locations on the map. After that i created a ...
3
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0answers
360 views

What is the area that OGR extracts from the (geometry) shp files for polygons?

The ESRI July 1998 technical documentation for polygon shapefiles at page 10 makes no mention of either area measures or length measures (apart from byte/record-layout matters). Yet OGR enables me to ...
3
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0answers
172 views

Polygon parcel division in python

Is there an open source tool or module in python that does parcel division of polygons like in ArcEditor?
3
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0answers
196 views

CartoCSS: Don't show border between adjacent polygons

In OSM, riverbeds are created as multiple adjacent or even overlapping polygons. When styling these polygons in CartoCSS with a border, the overlapping can be seen: I'd like to hide that line ...
3
votes
0answers
615 views

Closest set of points to another set of (predefined) points

I have 10 sets of points which I call templates that I have manually classified from 0 to 10. Each point is a X, Y coordinate in a text file. Each template has 5-8 points. I have new sets of points ...
3
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0answers
759 views

Can't find point/polygon intersect using QGIS (Windows only)

Below I describe the method I am using. I have two machines: ubuntu linux, qgis 1.4 - intersection works WIN xp, qgis 1.8 - intersection does not work Hopefully, someone will find what I am doing ...
3
votes
1answer
3k views

How to set google map zoom to fit the screen & position infobox labels depending on the area of polygon

I am using google map's FusionTablesLayer and polygon to set layers of USA states. I am having problem in integrating following 2 things : a) Set zoom property, so map will fit to the screen. I know ...
3
votes
1answer
6k views

How to write a point-in-polygon query for Postgis?

I'm trying to write a query in Postgis which will return all rows where a dynamically changing longitude/latitude point resides within the geometric polygon of that row (in the geom column). This is ...
2
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0answers
27 views

Assign different colours to intersection between two polygons and difference area

I am quite new to GIS using R. I have two sets of data, upon which I could create two polygons like this: What I want to do is colour the common area (inner 'circle') and the space between borders. ...
2
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0answers
41 views

Creating polygons from binary image using QGIS

Here I got a binary image of buildings (black and white image) and I need to convert them to building polygons: The expected outcome will be a vector file with building polygons based on the image ...
2
votes
0answers
31 views

Behaviour ST_Intersection of 3D LINESTRING and 3D POLYGON - Z value with GEOS backend

I do not quite understand the behaviour of ST_Intersection applied to 3D geomerties when using the GEOS backend. Take this example: SELECT ST_AsText(ST_Intersection('POLYGON((1 1 1, 6 1 3, 6 4 3, 1 4 ...
2
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0answers
56 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
35 views

Is it possible to merge two polygons with a single touching point into one?

Is my understanding correct, namely that two polygons touching at a common point cannot be merged because the result would be a self-intersecting polygon? I know there are dozens of Q&A threads ...
2
votes
1answer
56 views

Dividing shapefile with many polygons into equal parts

I have a shapefile with hundreds of caribou movement corridors. using this data, I am trying to create a map displaying the frequency of use to determine important movement and migration pathways for ...
2
votes
0answers
42 views

Graduated color display of overlapping polygons in ArcMap

Is there a way to display overlapping polygons in a graduated color symbology based on the level of overlap within the same feature layer? For example, in one area of the map there are two polygons ...
2
votes
0answers
29 views

Removing a 'non-gap' gap from a polygon that straddles +/- 180 longitude; looking for an R-based, code solution

I am working with a set of polygons from here: http://lme.edc.uri.edu/index.php/digital-data. In the artic, there are several polygons that straddle the +/- 180 longitude line. These are single ...
2
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0answers
70 views

Extracting polygons from mbtiles

Currently, one can extract features within a bounding box from an mbtiles file using tilelive-copy. However there is no way to extract features within a polygon from an mbtiles file. The mbtiles-...
2
votes
0answers
48 views

Creating a continuous raster road network using Polygon to Raster in ArcGIS Pro?

I have a polygon forest road network that I would like to turn into a raster. I have attempted to use the ArcGIS Polygon to Raster tool, but whenever the majority of a cell falls outside of the ...
2
votes
0answers
208 views

Copy polygons to another layer with different attribute

I am working in QGIS 3.0.2-Girona. I am digitizing images in which there are rocks that can be encrusted, totally or partially, by algae. I want to have a polygon for the rock and one for the algae. ...
2
votes
0answers
43 views

Calculating individual width between buildings using ArcMap?

I have a building footprint shapefile and I would like to calculate the individual width between each building (i.e., adjacent building and across the street). I have looked at solutions which use the ...