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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What is the use of Union_analysis in arcpy? [closed]

arcpy.Union_analysis((parc, census), parc + "_Un")
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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: vector union produces a single feature only, same as the input layer

I have two layers in QGIS 3.16, a MultiPolygon layer with a single feature, the area of Papua New Guinea a MultiLineString layer of OpenStreetMap roads, clipped to the extent of the first layer ...
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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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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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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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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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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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1answer
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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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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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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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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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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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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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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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181 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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71 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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141 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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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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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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1answer
584 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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1answer
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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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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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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
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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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