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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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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
19 views

Calculating total built area over plot gives wrong results? [closed]

I use ArcGIS Desktop 10.6 with the Basic license. I have to calculate the built area for each plot over a municipality. For that, I have several layers like Building, plots, land classification and ...
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1answer
30 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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28 views

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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34 views

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
31 views

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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2answers
82 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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1answer
92 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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49 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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113 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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23 views

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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2answers
102 views

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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9 views

MySQL group union

I want MySQL to merge many geographies together to form a single shape. A zipcode table has a row 'shape' containing a perimeter from Uncle Sam. Definition here: https://www.db-fiddle.com/f/...
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34 views

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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1answer
38 views

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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1answer
24 views

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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124 views

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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0answers
274 views

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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0answers
52 views

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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3answers
142 views

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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2answers
150 views

Combining two spatial tables in PostGIS

I have two PostGIS tables with geometries. One with number attributes and one with letter attributes. Each table has two features (rows). I would like to apply a operation on both stables so that I ...
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1answer
266 views

Only union/dissolve intersecting features to save time?

I have one table of about 300k polygons, some overlapping but most do not. I need to dissolve the overlapping ones and also keep the non-overlapping ones. I only need the geometries, no attributes. I ...
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3answers
171 views

Using postgis to flatten all polygons in table

I have a table with many polygons. The polygons all have a name and a value. I want to flatten these polygons so that each polygon border remains as border to the resulting polygons. Instead of ...
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1answer
165 views

Speed up intersection, union in PostGIS?

I have three tables: water, wetlands and parcels. I want to update parcel table with area that is covered by water or wetland (they can overlap). So I want to Merge water with wetland Dissolve and ...
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1answer
45 views

Using Union in ArcPy for ArcGIS Pro results in two fields with same name?

I just performed a union in my Python script between 2 features that both had a field attribute named "FLD_ZONE". My hope was that one of those attributes (for the second feature, I assumed) would be ...
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1answer
158 views

RuntimeError: Object: Error in executing tool when running Union

I have a list of a 2 layers (nfhl_fld_haz_features, prelim_fld_haz_features) and a feature class (master_merge) that I want to perform a union on: wkflw2_union = arcpy.Union_analysis([master_merge, ...
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0answers
118 views

Using Union tool in QGIS?

Here is my scenario: I am trying to use Union to combine the land and mangrove shapefiles in QGIS and to compute for the areas of each individual geometry. What I did: First, I cleaned them. Upon ...
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0answers
129 views

Dealing with a hole (or inner ring) at the intersection of two MultiPolygon polygons in Python Shapely

I have a problem with Shapely geometry object MultiPolygon (the exact data is shown below) in Python. I need to find a way to merge the small grid cell polygon with the larger polygon but after ...
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1answer
34 views

QGIS Union erroneously creating gaps

I'm trying to do a union between two Polygon Shapefiles, but when I do Vector > Geoprocessing Tools > Union I have the odd issue where most of it works fine, but some areas are returned in the union ...
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1answer
57 views

R sf extrapolate grid from centroids

I've got a grid/raster in R that is represented as centroids of the grid instead of polygons. I am trying to merge that with points. library(sf) nc <- st_read(system.file("shape/nc.shp", package="...
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1answer
92 views

How exactly do I use the GeoDjango Union function?

I have two models in my application: class Organization(models.Model): consortium = models.ForeignKey('Consortium') org_map = models.MultiPolygonField() class Consortium(models.Model): ...
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0answers
366 views

ArcGIS Repair geometry doesn't solve “Incomplete void poly” error

I'm working with 8 shapefiles at approximately 63 mb in size total and I am trying to use ArcGIS/arcpy's Union to combine them into one single dataset. Each time I run this, I get the error: ...
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1answer
166 views

Dissolve/merge polygons using ST_Union in CARTO

I am attempting to dissolve the boundaries between several polygons using a common attribute within a column in CARTO and the ST_Union function. In my scenario, I have created a table for all US Zip ...
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1answer
25 views

Deleting lines after manual union in ArcMap?

I have a question regarding the editing tools. I have made this selections of lines then used the "union" tool to make them into one entity but the lines that were merged together are still on my ...
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2answers
197 views

arcpy Geometry.union(Geometry) ValueError

In this script, I want to extract several polylines from one polyline. The data comes from this link : Lignes aériennes RTE au 22 décembre 2017 INF 45 kV In the flow, I merge the extracted polylines ...
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1answer
36 views

Union of Polygons with slightly shifted coordinates

I am trying to join some polygons using ST_Union but I am facing some problems due to slightly shifted coordinates of the polygons. Here's an small example of two polygons I would like to merge: The ...
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1answer
37 views

Spatial Overlay or Join with Ranking Logic?

I have two vector polygon files. One is flood zones and the other is parcels. I need to add the flood zone category to the parcel file, this is easy enough. However, some of the parcels have ...
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1answer
173 views

ArcMap Way to merge two shapefiles and take the average of their polygons that overlap?

So I have two shapefiles that show storm surge height values for two different areas. Nevertheless, they overlap for a good portion of their areas. When I merge them together, it seems that the ...
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1answer
94 views

Union from all feature classes from feature set using ListFeatureClasses

I want to use the union tool in ModelBuilder to combine ALL the features from two feature data sets from two different gdb together. I use ArcGIS 10.5.1 with an advanced license. I tried to use the ...
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2answers
56 views

Vector layers seem not to be aligned when performing 'union' in qgis

I have two files (shapefiles). A file with 50x50 meter cells. and a grid with 100 by 100 meter cells. I want to do 'union' so that I know which 4 cells of the 50x50 meter vector layer make up one cell ...
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0answers
128 views

Intersection throws com.vividsolutions.jts.geom.TopologyException: Found null DirectedEdge

When I make union of 379202 List<Polygon> rectangles rectangles and execute intersection with bounds UnaryUnionOp.union(rectangles).intersection(bounds) then I get: com.vividsolutions.jts.geom....
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1answer
443 views

Why gdf.explode() doesn't work?

I'm trying to merge 2 geodataframes and combine all entities. So I use : cloudNshadow = gpd.overlay(cloud, shadow, how='union') cloudNshadow = cloudNshadow.unary_union() But it returns me : ...
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0answers
729 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(...
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1answer
2k views

Shapely polygon union results in strange artifacts of tiny, non-overlapping areas

I am not sure if this is a shapely bug or a problem with my polygons. I have a bunch of polygons that look like this: They are level-12 watersheds provided by HydroBasins, and are presumably non-...
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1answer
738 views

How to self union a GeoDataFrame?

I have a GeoPandas dataframe with lines all originating in the same location. I want to partition the lines into segments and merge them to get a dataframe containing all the unique segments. I tried ...
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3answers
100 views

Union of two Point Features which are close to each other, but have got an offset?

I have one Point Shapefile with the correct geographic position, lets call it A. I have another Point Shapefile with the attributes I need, but with an offset of 0,7m or so (it varies a bit from ...
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1answer
221 views

union of two polygon layers is giving an empty line layer

I have created new temporary layers with selected features for the two layers .Then I am trying to do union of the two said temporary layers. temporary layer1 if ('Districts'==layer.name()): ...
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2answers
234 views

Is their an equivalent of SpChFIDS for a spatial POINTS data frame?

This code: seattle <- spChFIDs(seattle.shp, paste("seattle.shp", row.names(seattle.shp), sep=".")) Results in this error: Error in (function (...
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1answer
295 views

Summing Specific Features of Overlapping Layers

I have several layers that are separated by categories (1-5 being 1 low importance and 5 high importance). Each layer only possesses 1 value. I merged two layers simply using the Merge Vector ...
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1answer
55 views

how to ensure topology using v.overlay?

Trying to find the maximum of a several Shapefiles I execute a cascade of unions. Out of all the tools, so far GRASS v.overlay seems to be the one working the best. However I am running into trouble ...