Questions tagged [union]

In set theory, the union (denoted by ∪) of a collection of sets is the set of all distinct elements in the collection. It is one of the fundamental operations through which sets can be combined and related to each other.

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'union' between spatial polygons and spatial points in R

I have a gridded map shapefile with grid identifier cells (gid). dput(head(grid)) structure(list(gid = c("183253", "183254", "183255", "183256", "183258&...
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Identify objectID of multiline to connect them in ArcPy

I have two sheets; in each there is a road network, but drawn by different people. Now I want to connect those lines that are intersected by the index sheets as I shown below, but what I found is some ...
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Move values from united columns (union)

I am looking for a way to move values from united columns (union). Using the Union command, I have merged several cleansed layers. Each source layer has the same columns (topic). Using the Union ...
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QGIS: Union: Could not add MultiStringZ object to MultiPolygonZ layer

I made some models in QGIS, mostly with the algorithms Union, Aggregate and Field Calculator while also using Fix geometries en Multipart to Singlepart at the start. My output layer contains 7099 ...
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Why is my ST_Union output disproportionately large?

I have two multi-polygon geometry tables (see the figures below) in my PostGIS database and I would like to create a union of these two tables. They are ~12mb and ~1mb in size. However, the union of ...
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Merging multiple road network shapefiles

I have created multiple connected road network shapefiles of the same extent based on a subset of point locations with the v.net connect operation. I split the point locations into 4 equal point sets ...
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Union tool results in error: "GEOS geoprocessing error: intersection failed"

I am trying to use union processing on a number of overlapping polygons (approx 50-100) in the same layer. This raises the error "GEOS geoprocessing error: intersection failed", without any ...
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Using Union tool over MultiLineString in polygons layer in QGIS

I created a polygons layer in QGIS 3.22.2 by creating circular buffers around points. I need to Union them by intersecting the overlapping parts. After running for several hours, the Union tool gives ...
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Polygon Union not working in QGIS

I am completely new to QGIS, so this issue might be really easy but I'm at a total loss on how to proceed. I am attempting to combine datasets in QGIS utilizing the Polygon Union command, but am ...
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Multiple Unions & Dissolve for Buffers

I'm a new user of QGIS 3.10.4. I need to create contours on maps using buffer, union and dissolve functions in QGIS. The buffers will be from multiple points. Is there any way I can unionize and ...
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QGIS Union is slow. How to speed up or which alternative to use, creating the same output?

I have two polygon layers which I want to union. One layer (1) is just one big feature, the other (2) contains 250’000+ features. Layer 1 was created this way: Several polygons --> fix geometry --&...
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How to get union of multiple linestrings and polygons in Google Earth Engine?

I want to get the union of a list of multiple LineStrings and Polygons. The variable geoLeyte contains this list, but if I want to use the .dissolve() attribute, it gives an error. Who could help me? ...
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How to get union of multiple polygons in Google Earth Engine?

I would like to get the union of m (m is variable) different (multi)polygons in Google Earth Engine. The attribute .union() only works with two polygons. See example below for what I have till now. ...
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Merging two shapefiles with disparate attributes and keeping attributes of both using QGIS

I have two shapefiles of NYC--one of city council districts and another shapefile of the census blocks inside NYC. I want to merge these two shapefiles so that I can see what blocks lie inside of each ...
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ArcMap adjacency dissolve question - based on missing data in YR field

In my polygon shapefile, that was provided by a govt agency, there are thousands of records with DATAYR=0 which is entry error. How do I dissolve/merge/union (doesn’t matter which operation) where ...
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PostGIS - ST_Union + ST_Difference create extra line segment

Very similar to this question I have two multipolygons, which touch/overalp each over. please see this link for the multipolygon #1 and multipolygon #2 multipolygon #1 multipolygon #2 I ran st_union ...
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Compound contiguous links to lines in a network and find isolated lines

I want to compound the red and green links (lines between the poinst) to one or more lines. I need it to finde the green links that not touching the red lines in my network. Step 1: compound touching ...
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Union multiple vector layers in QGIS

When combining two layers the "Union" tool works fine, and I have used Union several times: A + B => AB, then AB + C => ABC, then ABC + D => ABCD, and then ABCD + E => ABCDE and ...
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Transform GeoJSON shape with 2 requirements

We have this shape in GeoJSON: https://gist.github.com/panchicore/0324b0e366211c3d907b1c42f54db9c9 And the expected output is: Outer side (frontiers) sticks to its country frontiers (given the ...
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5 votes
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Getting the 'composite' of two polygon layers

I have two table of polygons, and I want to 'flatten' them into one table, and have the result tell me which areas are in one table of polygons, which in the other table of polygons, and which are in ...
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Use ArcMap to record dominant land classification per DEA in Ireland [duplicate]

I have a shapefile consisting of Ireland District Electoral Areas (DEA), in which there are over 3000 polygons. Secondly, I have a shapefile consisting of the Land Use classifications in Ireland. A ...
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Classifying a shapefile after a union

I am trying to classify the Electoral Divisions of Ireland into their land use. To do this, I have obtained the Electoral Divisions shapefile (there are over 3000 polygons), and the Corine Land Cover (...
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Does UNION in PostGIS check for distinct geometries, or only other fields?

I've been getting some funny behaviour from UNION vs. UNION ALL when combining two tables in PostGIS, so just wanted to check: Does UNION include a check for duplicate geometries when determining rows ...
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Convert lines to polygons, but closing the lines first (topographic lines not closed)

I have a topographic layer for a country. I want to select topographic lines of a certain altitude and transform the lines to polygons. All work fine except one thing: since the lines of the ...
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2 answers
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Looking for a Tool, that allows me to "Union" many overlapping layers, while prioritizing some to overwrite the others in ArcGIS

I am currently working on a project where I analyze the contents of a 500m buffer around several sample points. Foundation for those informations are multiple shape file layers, which, alltogether, ...
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Union of multiple shapefiles (polygons) in ArcMap creates random vertical and horizontal lines (sections) in output

I have made a union of 4 features (polygon shapefiles) in ArcMap. However in the final output it has made random completely vertical/horizontal lines/sections in the final union. So it should look ...
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4 votes
1 answer
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Getting all of combinations of features found on two layers using QGIS

This is a problem that seems like it should be simple, but it's a little difficult to explain. I have two polygon layers, each with a few hundred features (specifically the districts of England and ...
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3 votes
1 answer
88 views

pyqgis 3 Union multiple layers using temporary layers

I would like to use the tool "Union" to union 3 different layers. This tool unfortunately can union only 2 layers so I have to run it twice. First I run it to union the layers "Layer1&...
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Using Union in ArcGIS Pro

I cannot see how Union is being used; why in this instance and whether it produces the desired results. I am posting the procedure for some clarity. I don't understand the selection its asking for ...
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1 answer
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Union of shapefiles to generate composite shapefile with overlap frequency count for each polygon

I'm new to QGIS, making the switch from ArcMap. I have 5 shapefiles of polygons representing 5 years of insect defoliation. I need to overlay the 5 years and create a new composite shapefile that is a ...
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2 votes
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Joining (merge, union) non-overlapping vector polygons with QGIS

I look for a solution how I can join several polygons that do not overlap with each other and have no common sides, by creating a new polygon. That is, it should be an output polygon covering the &...
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201 views

Finding details of both overlapping shapes using ArcGIS Pro without Advanced level license

After Understanding Union analysis output using single feature class with overlapping polygons in ArcGIS Pro I now have a better understanding of that tool. However, I have a single polygon Feature ...
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Understanding Union analysis output using single feature class with overlapping polygons in ArcGIS Pro

I have a single polygon Feature class with about 33,000 shapes. I'm looking for overlaps. I want to be able to say "Shape x overlaps with Shape y and Shape z" So the UNION analysis tool ...
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5 votes
3 answers
655 views

Count overlapping features using Geopandas

Is there a way to easily count overlapping polygons using Geopandas, the same way as the ArcGIS Pro Count Overlapping Features works? So far my approach was to do union overlay and then dissolve with ...
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QGIS Union: Could not add feature with geometry type GeometryCollection to layer of type MultiPolygon

I overlay several Shapefile layers with Vector > Geoprocessing Tools > Union in QGIS. The first five layers do work. However, when I'm trying to add another layer I receive the following error ...
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5 votes
1 answer
319 views

Merge and Delete with priority overlapping polygons QGIS

I have two shapefiles with polygons: one is regions for a country and the other is the protected areas inside that country. I have merged these two polygons with Union, but the regions and protected ...
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Are there limits on the number of unique polygons created by the QGIS Union tool?

Is there a limit on the number of polygons that the Union tool will compute? I have overlapping radii from a variety of sources pictured below, but the tool continues to give me an "GEOS ...
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Why use st_union after st_combine with sf?

The documentation of the st_union function of sf is not clear (for me!) on one point: what are the action and result of the function when applied to an sfc with a single feature, with the parameter ...
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2 votes
1 answer
312 views

Merging two multipolygon tables into one and afterwards dissolving boundaries using PostGIS

I am trying to merge two multipolygon tables into one and at the same time - in the same query - dissolve the boundaries between the polygon districts using postgis. The two tables are the red ...
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1 vote
1 answer
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Reading or creating empty shapefile in R

I have several polygon shapefiles that I need to merge into one using a loop in R. I want to start with an empty shapefile and merge it with the existing shapefiles. All shapefiles will be chacked ...
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Finding union of many geodataframes using GeoPandas

I have a series of many GeoPandas Polygon objects, each with an associated exposure time. My goal is to find the union of all the Polygons in order to create an exposure time map. For each Polygon in ...
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1 vote
1 answer
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QGIS Dissolve/merge features that overlap

I have a vector layer that I created through classifying an image, isolating a specific class (raster calculator), polygonize, and then created a buffer. I am trying to merge/dissolve/union the ...
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2 votes
1 answer
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Calculating apportionment on the client-side in JavaScript map?

I have a set of census polygons (P1... P4) containing population information, and I'm building a tool using the ArcGIS Server JavaScript API whereby the user can draw an arbitrary shape: I need to ...
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2 votes
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Intersect overlapping entities and their attributes

I have a shapefile containing 6 classes of polygons on QGis 3.14. Some of these polygons overlap each others, but they're not geometry errors or duplicates, just polygons with different attributes. ...
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Calculating the area of the polygon segments within multiple overlapping buffers

Let me try to explain my problem: I have a layer of polygons A layer of overlapping buffers I want to calculate the area per buffer of the containing polygons. The problem is that the buffers are ...
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1 vote
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Join the fields (column) into headers after geoprocessing

I am new on QGIS, I will try to be as specific as possible, but it seems quite hard to explain... I am working with a first polygon vector: species' territories [In the attributes table: 50 lines, for ...
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2 votes
1 answer
183 views

PostGIS ST_Union with IF statement

I have a dataset containing buildings where each building has a certain value/score. What I want to do is make clusters of these buildings depending on their values/scores. What I did so far is; I ...
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1 vote
2 answers
232 views

Buffer and Dissolve/Union 2 million points

I'm looking for a solution that will let me add a 100m buffer around 2 million points and then dissolve/union that output into a single multipart polygon. On a much smaller scale (100 points) using R ...
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2 votes
3 answers
507 views

Using PostGIS to generate a polygon representing the area shared by some (but not all) of a set of polygons

I have an application where several users submit polygons, and I am looking to create an aggregate polygon that represents a kind of average of their submissions. We use PostGIS for our spatial ...
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1 answer
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Using Union tool without optional overlay layer

In QGIS 3.10.3, I'm trying to figure out how to use the Union tool without the optional overlay layer. When I go to "Vector > Geoprocessing Tools > Union..." and bring up the tool, the ...
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