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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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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How does Union resolve overlapping features if one of the inputs has self-overlaps

For the ArcGIS Pro Tool Union, how does it resolve overlaps in one of the inputs? A normal union example is input 1 overlaps input 2. Usually this would result in a feature being created that has ...
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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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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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Vector Union function performance in QGIS and ArcGIS DEsktop [duplicate]

I am trying to find the union of two vector layers (both spatial indexed) - one land use polygons and another grid. In QGIS it is running since 4 days ago, but in ArcGIS Desktop it took less than 10 ...
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Handling NULL values in QGIS

I am using QGIS to make some boundaries adjustments of the Italian provinces over the years. I have a shapefile with the provincial boundaries in 1961 and another one with the boundaries in 2001. No ...
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77 views

Dissolve polygon by attribute or featurecollection by property in Google Earth Engine?

I would like to dissolve a polygon/featurecollection in GEE to run some statistics by the country level. I have tried union and dissolve and cannot find a solution. Union dissolves everything to get ...
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1answer
59 views

Combining polygon features and retaining both geometries and attributes using `sf`

I use the sf R package regularly, but I'm having trouble finding the correct process to use in sf to get a parallel result to what I would get performing a union in ArcGIS. Given the image below, ...
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Getting shapefile in which both non-overlapping and intersected polygons are present using ArcMap

I have a polygon shapefile (Shapefile-A). In this shapefile there are some polygons which overlap and some don't overlap. I want to take intersection of these overlapping polygons and make a new ...
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1answer
54 views

Find features based on total overlap of another feature class

I have 2 polygon feature class's (A and B) that overlap each other. I want to select all the polygons of feature class A where the total overlapping area of feature class B polygons is less than 10m2 ...
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57 views

Select points within a buffer around a line

Working with PostgreSQL. I have a Table with streets (Linestrings), and a Table with accidents (Points). The streets are divided into sections. I want to find the accidents within 50m around a certain ...
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Aggregating numerous polygons into one with PostGIS

I have this PostGIS query which aggregates many polygons according to a variable ("region"): SELECT ST_AsGeoJSON((ST_Collect(polygons)),3) as geom FROM table GROUP BY region; The ST_Collect returns ...
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Failing Unions due to Non-Noded Intersections

I'm trying to perform lots of unions in GeoPandas. I've got around fifty sets of between 7-12 GeoDataFrames of the same place at different times that I'm trying to union into one layer per set. Right ...
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Progressive union of a large number of multiband rasters in PostGIS

I am deriving multiband rasters from airborne lidar imagery, and loading these into PostGIS along with associated metadata. Raster cell values are counts of certain point classes over a series of ...
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35 views

Making union of some raster coverages without the area between them

I have a set of raster coverages. Some of them are really far from each other. When I use ST_Union function to union them, the function fill the area between them. I explain it in a simple example: I ...
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Phanton lines in a PostGIS ST_Union

I created a polygon using ST_UNION. However, it shows some lines inside that don't make sense, as you can see below. How can I create the union poly without those lines or remove it from the poly ...
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Union multiple layers with OGRVRTUnionLayer

I'm trying to union overlay layers using OGRVRTUnionLayers. However, it keeps the new records on new rows as opposed to appending the data to the same row (So you would expect to get back all data but ...
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Union of two different shapefiles GDAL

With Python 3 and GDAL package, I am trying to merge two shapefiles that come with databases. They come with the following files: grade_id14.cpg grade_id14.dbf grade_id14.prj grade_id14.sbn ...
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Union by new category using R and sf

I'd like to create a new shapefile or a new geometry variable that allows me to plot borders around regions in R. I'm using the sf and mapping with tmap. Basically, I'm adding a character vector to an ...
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32 views

Selection by Location on Raster, Using a Vector Layer

I'm trying to identify raster cells by location to eventually convert them to vector polygons, and then add them to an existing vector layer. Below is a picture to illustrate the problem. The green ...
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PostGIS - Tables UNION

I have three tables (Table_1, Table_2, Table_3) with the same fields: geom, Field_a, Field_b, Field_c, Field_d. I want to SELECT these tables so that all their rows appear but I want do not want rows ...
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Union Tool creating slivers in ArcGIS Desktop?

I am using ArcGIS Desktop 10.4. I have 2 feature classes in the same GDB. One feature class is a subset of the other one (i.e. it's a direct copy, with a subset of features retained, the others ...
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Performing Union_analysis on outputs created with arcpy.GetParameterAsText()?

I am trying to write a script tool for my geospatial programming class and I am stuck (this is an online course and we get NO support from our instructor). What I need to do is create buffers (...
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306 views

st_write fails for object created with st_difference using R?

Using publicly available sea area shapefiles bahamas: http://www.marineregions.org/gazetteer.php?p=details&id=8404 ("eez.zip") watl: http://www.marineregions.org/gazetteer.php?p=details&id=...
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How to do a union and specify that polygons must be greater than a certain area (e.g. 0.1 acres or greater)

I am doing a Union (or possibly an identity) of several polygon layers. I want to the result to contain only polygons .05 acres or greater, but do not want to eliminate any area. How do I ...
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How to recognize original group from unified set of polygons in R

I have simple question. How can I know the original group after apply z = sf::st_union(x, y)? I have 2 sets: length(x[[1]]) = 4253, length(y[[1]]) = 91. Finally, I have z of lenght 411 but don't know ...
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Attribute table After Union

I did a union of 2 layers, which technically represent the same thing but one is the updated version. This means that there is a common field in both, lets call it A. After I did the union, I opened ...
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ArcMap: Combining County Polygons for 3 separate states into one layer with attributes

I have 3 separate layers with the counties for 3 separate states: WA, OR, & ID. I want to combine them into one layer "Counties" so they all share an attribute table with the same fields. I am ...
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1answer
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Dividing/tiling input features in FME, processing independently and fanning out the output by tile

I have two heavy-weight polygon feature classes that I want to union and then calculate some area-weighted average of one attribute for each aggregate (say parcel polygons, which is one of the inputs) ...
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70 views

QGIS (merging, dissolve, union) lines of same name

I have street data where roads are segmented for no particular reason. I want to merge, dissolve or union whatever seems fit to make a single flat line. I H have tried above processes in QGIS but ...
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575 views

Union, merge, intersection, join layers - logical difference and clear explanation for QGIS

I note that there are answers available on the difference between join and merge (e.g., Difference between 'join' and 'merge'?) that link to ArcGIS resources as a reference. However, I ...
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254 views

Cascading union OGR Multipolygons?

I have 2 OGR Multipolygons that intersect, hence I want to cascade Union them. I tried this but it returns me empty and doesn't union it. Seems this works only on Polygons and not Mul;tipolygons. What'...
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Dissolve only overlapping polygons in R using sf

I extracted information from open street map that contains many polygons, some of them overlapping. I want to union all polygons that overlap with other polygons. This question has been asked before ...
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1answer
374 views

Why does fasterize gives different output for multipolygons with and without internally resolved boundaries?

I was thrilled to be clued into the package fasterize, which speeds up the rasterization process in R tremendously. However, I cannot figure out why the fasterize() function outputs two different ...
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Build measure of state change

I want to be able to build a measure in ArcGIS (ArcMap). (1) I have some shapefiles of sovereign states by centuries. These are polygons with the name of the state as ID. (2) Moreover, I have a ...
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Locating observations that lies within a collection of Polygons (Python)

I'm trying to locate the observations that lie within a collection of Polygons but my current implementation takes forever, and I suspect that it is because the 'within' method needs to check all ...
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1answer
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What do you call this combination of two district maps?

My real-world problem is that I want to combine state House and Senate legislative districts so that a user can pick a region (not a point) on a map that is included in both their House and Senate ...
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164 views

ST_Union in PostgreSQL and QGIS

I have a problem with understanding of the ST_Union (PostgreSQL) and the union function in QGIS. Basically, I have as an example two layers A and B that overlap. The result when using union in QGIS is ...
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244 views

Using ST_UNION to combine several polygons to one MULTIPOLYGON using PostGIS?

I have a problem with ST_UNION So, I have a several polygons DB looks like this I need UNION all off those polygons to one multipolygon and get result that looks like this I tried use ST_UNION ...
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1answer
239 views

How to remove artifacts with SQL Server GEOMETRTY::UnionAggregate()

We'd like to do an effective "real-time dissolve" on an Esri feature class with a SQL GEOMETRY shape where a parcel layer is "dissolved" into products using an attribute (ProductID) of the parcel ...
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392 views

Shapely : cascaded_union seems to return too many polygons

I'm trying to get the union of around 4,000 polygons using Shapely's cascaded_union function. The output of this function is a multipolygon in my case, which is normal since many input polygons do not ...
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Union very large layer in FGDB and only keep one polygon that is overlapping?

I'm trying to union an exceptionally large layer (45k features) of footprints with many of them largely overlapping. I'd like to union this layer but I'm having trouble due to the size of it. The end ...
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What is the proper name for the “Venn diagram” of a set of geometries?

Sometimes, you have a set of overlapping geometries, and you want to generate an output like this: Image taken from this answer. The resulting polygons have no overlaps; each region of space is ...
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QGIS 2.18.14 valid option for union tool?

Using QGIS 2.18.14 there is no satisfying Union method. The integrated QGIS Union tool generates incorrect outputs if complex polygons (e.g. street network) are used. The SAGA Union Module does not ...
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Filter four features from a vector shapefile to create a new layer to perform buffer, intersection and union on it, in QGIS 2.18?

From a dataset that contains points of interest defined by type of object with four different features, I am trying to distinguish the features to perform different analysis. Thought I had to filter ...
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Merging layers with preferences or ranks using ArcGIS Desktop?

I want to make a "Mosaic" or a "Compilation" of 20 shp. layers which some of them are overlap. The layers has a field named "Year" and I want the newest be on top and delete the overlap older shps ...
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Why is Union in ArcMap much faster than other approaches? [closed]

Taking the union* of these two large shapefiles file1 file2 locally using ArcMap takes appr. 10 min. Over the last few weeks, I've tried to obtain the same results using other, open-source ...
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Overlay Union Geopandas improve performance

How to speed up the "union" of two shapefiles using geopandas? I have two large shapefiles: geodataframe_left.shape = (3610, 12) (500 MB) (link) geodataframe_right.shape = (16396, 3) (200 MB) (link)...
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Seeking UNIX alternative for ArcMap Union with good performance?

I've been trying to create a union* of two shapefiles using a Unix-based approach. So far without success. My two shapefiles can be found here. The process using Union (analysis) takes ...
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Seeking PostGIS equivalent to GeoPandas union overlay?

What is the PostGIS / PostgreSQL equivalent of the GeoPandas Overlay Union operation? res_union = geopandas.overlay(df1, df2, how='union') Say I have two tables, 1 green, 1 red with each with two ...

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