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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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42 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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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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34 views

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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24 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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1answer
33 views

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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32 views

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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62 views

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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1answer
30 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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2answers
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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
157 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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1answer
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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
56 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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282 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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135 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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2answers
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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
230 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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32 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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54 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
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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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2answers
119 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
196 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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170 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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284 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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151 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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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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38 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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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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717 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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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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4answers
276 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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260 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
496 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
246 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
409 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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70 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
328 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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233 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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273 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
43 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 ...