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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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How to associate point to most recent date in overlapping polygons? (Union & v.clean is giving errors.)

I am trying to associate presence points (where a bird was sighted) in a given month (e.g. December 2022) to the most recent fire that occurred in that area. I am planning on generating a raster (5km ...
Frek's user avatar
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2 answers
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How to union two polygon shapefiles by one or more attribute fields in QGIS

I would like to union two polygons that have the exact same fields in their attribute tables in QGIS. However when I use the Union tool, it makes an attribute table that has exactly twice the amount ...
MapDeath's user avatar
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QGIS - Unite many lines in a single Multiline (with branches)

I have a shapefile that contains many lines that connect to each other, forming branches, as shown in the picture: How can I join all these lines into a single entity? I want the attribute table to ...
Daniel Möller's user avatar
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R library or tool to do spatial apportionment

Please tell me there is a package to do spatial apportionment. I find spReapportion on GitHub that's 7 years old and this tutorial, which was made with R 3.0.1 (May 2013). I'm trying to script the ...
Mox's user avatar
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2 votes
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Using Union tool in QGIS creates gaps and overlaps

After using the Union tool on QGIS I get hundreds of gaps and overlaps between polygons on the resulting shapefile. If I zoom to the fullest on those gaps and overlaps they are always lines, they ...
Gonçalo Coimbra's user avatar
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Union tools for polyline in ArcGIS

I'm trying to combine 2 polylines into one with all features and their attributes will be written to the output feature class. I'm trying to use the Union tools but it won't work on polyline, any help?...
igedeari's user avatar
2 votes
1 answer
123 views

Calculate the ratio of intersection to union in using the field calculator in QGIS

I have two separate polygon layers, A and B, of which I want to calculate the intersection to union ratio and store it as an attribute to polygon A. To do this, one needs to divide the area of the ...
saQuist's user avatar
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Could not add feature with geometry type MultiLineString to layer of type MultiPolygon [duplicate]

I´m trying to make the Union of two shapefiles on QGIS 3.28.9 and keep getting this error message: Feature could not be written to Union_8f811877_53f7_4317_ae22_fe05e7ab9695: Could not add feature ...
Gonçalo Coimbra's user avatar
3 votes
2 answers
251 views

Unifying touching polygon within polygon geometry in PostGIS

I have a polygon geometry with 100+ polygons originally converted from a raster table - see the below image Zoomed view of one of the polygons I would like to unify the touching polygons (i.e. ...
rm167's user avatar
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2 votes
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PostGIS: Overlay without dissolving boundaries (Union) & keeping attributes

Problem I need a geometric union of a set of polygon layers (like Union in ArcGIS or QGIS) and because the datasets large and calculation time becomes very long in QGIS (I don't have an ArcGIS ...
chrisp66's user avatar
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1 answer
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st_union in R creates artifacts for global data

I load this polygon data in R which global coverage. https://drive.google.com/file/d/1E-atD4ZhbaQ8Zxv93sFgk9l_atLtG8eJ/view?usp=drive_link It looks like this: In QGIS I can run the dissolve function ...
Lenn's user avatar
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TypeError: a.union is not a function

I'm trying to get the union of two polygons but every time I try I get a TypeError: a.union is not a function error. Here's my code: import GeoJSONReader from 'jsts/org/locationtech/jts/io/...
neubert's user avatar
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3 votes
1 answer
325 views

Self union MultiPolygon layer using GeoPandas

I need to perform a union operation inside a single layer. In QGIS there is an option not to select the second layer, but I can't figure out how to do it in GeoPandas? Example: Plots are red, zones ...
Sergey47's user avatar
1 vote
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Merge polygons that overlap into a multipart polygon while maintaining the original geometries/look

Overall, I want to display an index map that shows nautical charts and their corresponding inset charts. The majority of the time these insets lay directly on top of the "parent" chart in a ...
Sjolster31's user avatar
10 votes
1 answer
136 views

Merging layers and excluding some of the products in QGIS

When merging two layers of polygons so that they produce a third layer where no polygon contains another polygon, I find that the product contains some very small polygons, almost too small to see. ...
Lee Goddard's user avatar
1 vote
1 answer
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PostGIS concatenating tables with different SRIDs side-effects for area

I am quite new to Postgres/PostGIS and have an open question regarding 'mixing' tables with different SRIDs. I know this is generally not recommended, but in my case, I will already be required to ...
Bullfrog3655's user avatar
2 votes
1 answer
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How to combine buffered rivers and landcover type in earth engine to get union?

I want to pull one cover type from an image collection (NLCD) and combine it with buffered river data, a feature collection, with the result being a binary image containing the union or sum of the two....
highlandmain's user avatar
1 vote
0 answers
149 views

QGIS sum attribute values of overlapping line segments

This is sort of follow-up to this thread. Not sure how I got it working a year ago, but now I'm across the same issue again. Here is a clean dataset which I believe is correct. It contains overlapping ...
edge's user avatar
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Creating unique ID for overlapping polygons in QGIS

In QGIS I created a union from a layer that had a lot of overlapping polygons. In the union layer, I used the Field Calculator (see the formula I used below) to count how many overlaps there were, as ...
Ronnie Lane's user avatar
2 votes
1 answer
72 views

Using %n% inline variable as %n%-1 with Iterate Feature Classes iterator

I am new to ArcGIS Pro and have just a "Basic" license. I have no Python coding experience. I am trying to make a ModelBuilder tool that will Union multiple feature classes (as little as two ...
Bob's user avatar
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Getting percentage of parcels covered by slope polygon file using ArcGIS Pro without using Identity?

I've read the other similar stack questions and they weren't helpful, as in the processes didn't work or there was some ambiguous field references that may have contributed to my confusion and error. ...
Scott Jordan's user avatar
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1 answer
280 views

'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&...
Shunrei's user avatar
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6 votes
2 answers
1k views

Creating Virtual Layer as union of multiple layers with same schema in QGIS

I have a Layer Group surveyor with lots of layers (shapefiles) with seemingly random names, and with identical schemas. I would like to combine them all to one layer; preferably with a Virtual Layer. ...
Mads Skjern's user avatar
2 votes
0 answers
31 views

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 ...
saraghafri's user avatar
1 vote
0 answers
92 views

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 ...
Ma Fo's user avatar
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2 votes
1 answer
841 views

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 ...
Rik's user avatar
  • 31
4 votes
2 answers
555 views

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 ...
rm167's user avatar
  • 469
3 votes
1 answer
1k views

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 ...
David Hasselberg's user avatar
5 votes
3 answers
2k views

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 ...
edge's user avatar
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3 votes
1 answer
622 views

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 ...
Pyrotechnical's user avatar
4 votes
1 answer
295 views

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 ...
zaido141's user avatar
3 votes
2 answers
1k views

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 --&...
Motti's user avatar
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1 answer
186 views

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? ...
justin fiedler's user avatar
0 votes
1 answer
3k views

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. ...
justin fiedler's user avatar
1 vote
1 answer
1k views

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 ...
eric andre the gian's user avatar
1 vote
0 answers
25 views

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 ...
Phillip Murray's user avatar
2 votes
0 answers
213 views

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 ...
Tony's user avatar
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4 votes
1 answer
273 views

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 ...
Tibor's user avatar
  • 375
5 votes
1 answer
3k views

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 ...
Åke Eriksson's user avatar
1 vote
1 answer
66 views

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 ...
panchicore's user avatar
6 votes
1 answer
205 views

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 ...
TheRealJimShady's user avatar
0 votes
0 answers
43 views

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 (...
Guest_question's user avatar
3 votes
1 answer
174 views

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 ...
MDB's user avatar
  • 155
3 votes
1 answer
669 views

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 ...
M. Beausoleil's user avatar
3 votes
2 answers
256 views

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, ...
Mangoayran's user avatar
1 vote
0 answers
97 views

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 ...
hbk's user avatar
  • 434
4 votes
1 answer
210 views

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 ...
James McL.'s user avatar
3 votes
1 answer
392 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&...
SaskiaG's user avatar
  • 429
0 votes
0 answers
119 views

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 ...
Talron's user avatar
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5 votes
1 answer
530 views

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 ...
Dicerca's user avatar
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