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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Union or Times for overlaying two maps?

I have created two different raster maps by Kernel density, one for street connectivity density and one for residential units density. I classified each of them in 5 classes with high density, high-...
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37 views

PostGis - st_union polygons, keep sum of attribute

There are multiple My current query is: SELECT (ST_Dump( ST_Union( way ) )).geom AS way, 10000 AS way_pixels FROM ( SELECT way, way_pixels, ...
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27 views

Attempting to “merge” 3 polygon layers together, not sure if merge is correct

I have three separate polygon layers. Some of the sections in the different layers overlap. I want to "merge" all three layers together and create one layer that is representative of the entire area ...
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17 views

ArcGIS Overlay route events

I have bus onboard volume data stored as a polyline shp file. The polyline lengths are the distances between sequential boardings and alightings. So along any particular bus route there are ...
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50 views

Is it possible to intersect multiple polygon shapefiles to identify areas where two or more layers overlap?

I have 19 polygon shapefile layers, with some occasionally overlapping with one another. As a final output, I would like a shapefile that includes only the overlapping areas between 2 or more of these ...
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1answer
26 views

Scripting a population sum based on union

I'm having trouble automating a process to sum one field into a new field, summing whenever the value of an FID field from my Union is the same. I'm looking to sum the population, stored in field "...
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30 views

Help with Python shapefile Union Program

First I am a Python noob... I have searched the database for this answer, found a few that might be the answer, just way over my head (I am signed up for a intro python class this month, to help ...
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48 views

DotSpatial Opposite of Featureset.Intersection

DotSpatial 1.8: I have some code to give me the intersection of my trip polyline and where it crosses key polygon regions. That works well: Dim fsResults As IFeatureSet = fsTripLne.Intersection(...
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1answer
28 views

Spatialite union more than two layers / tables

Is there a way to union or collect any number of layer geometries with Spatialite (or another spatial database)? Two is simple enough, but more than that becomes convoluted. For example, if all I want ...
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63 views

Union geometries from multiple tables

I need to create a "total" polygon by merging together all the geometries from about 10+ tables into one big polygon. For a test with just 2 tables I tried ST_UNION and ST_COLLECT, the result was 500,...
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1answer
31 views

ST_Union returning Null with Spatialite, even after ST_MakeValid

I am attempting to run ST_Union on some features in a GROUP BY Spatialite query, with the aim of counting the number of features, and the total area of those features, which may overlap so should not ...
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1answer
86 views

Setting threshold for unions in PostGIS?

I have a shape file of buffers. What I'm trying to do is to merge the buffers that intersect, but not just if any part of the buffers intersect. I would like to set a threshold, for let's say if 50% ...
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49 views

Limitations when running the Union tool with large datasets? [duplicate]

I'm running ArcGIS 10.3 with an Advanced License on a Windows 7 64x system with 20 GB of RAM and a 4th Gen Intel i7 Quadcore-CPU. I have a problem with the normally very efficient Union tool. What I'...
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2answers
101 views

Intersecting three polygon layers in ArcGIS?

I have three data sets of San Francisco, TerraSAR-X, ALOS-PALSAR, Radarsat2. I have extracted KML files using Envi Sarscape. In order to find the intersection of these areas, I have converted ...
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84 views

Problem in polygon division using the union tool from QGIS

I am trying to overlay two polygon layers using the union tool from QGIS, to then compute the areas from the resulting polygons. However, in the resulting layer some polygons are not divided as ...
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58 views

ArcGIS Union equivalent in PostgeSQL?

I am using pgAdmin (v.1.22) for my postgres(9.5). I am still fairly new to postgres. I am trying to perform a union(intersection) of multiple layers where there is both complete and no overlap between ...
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1answer
152 views

Count overlapping polygons, including duplicates

I am using ArcMap 10.2.2 (Advanced license, no toolbar add ons/no spatial analyst) on a Windows 7 computer (i7 processor, 8GB RAM). I have used ArcMap for other basic analyses and have only very basic ...
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1answer
117 views

Finding and merging lines that touch in PostGIS?

I would like to select and merge segments that touch like in the image below. My table contains single segments with their own id (shown in the figure), I just want to isolate single "group" of ...
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1answer
47 views

Combining field data from multiple shapefiles into one queryable layer using ArcGIS for Desktop? [closed]

How do you combine multiple field collected data set in shapefile form in to a single layer in ArcGIS 10.3 for Desktop?
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1answer
43 views

Cleaning up inexact polygon unions

I have geography data stored in SQL Server and I am trying to merge polygons from two data sets together. The problem is that they do not line up exactly, so unioning them results in narrow gaps ...
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1answer
45 views

Creating fishnet from thematic polygon data?

I need to create a regular grid containing attributes from other thematic data from ecological data. I am in effect creating a homogenous polygon raster and adding information from another dataset ...
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33 views

Which are the steps the union functon goes through? [closed]

While skimming the union function I could see it works with intersecting bounding boxes, layer features and attributes. But how, exactly does this function work; which are the lines that check for ...
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90 views

Union overlapping shapefiles (poylgons) and merge the attributes where overlap occurs in R

I have 30 shapefiles of overlapping polygons and would like to union them into one shapefile. The attribute table of the 30 layers is exactly the same (two columns, Type and Origin). A new polygon ...
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1answer
77 views

How do I perform a Union (as per ArcGIS and QGIS) in MapInfo

I am running MapInfo 15.0 and need to perform a Union of two polygon layers (i.e. combine the two and preserve all boundaries and associated attributes). I know there is some ambiguity over the term ...
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126 views

Merge line segments by length (in QGIS)

I have a layer containing line segments which are connected by their endpoints (e.g. as within a street network). I'd like to merge (union) polylines within this layer into one feature until following ...
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1answer
74 views

Dissolving a TIN using python/ogr binding

I have a TIN model where I remove some of the triangles (see fig. 1). Most of the triangles touch on one edge, some on one vertice. I would now like to generate a polygon shapefile containing the ...
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1answer
208 views

Union on lines using ArcPy?

Essentially I want to union multiple (20) congruent line shapefiles, where overlapping line segments in the input shapefiles are combined into a single resulting output shapefile. But I can't union ...
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1answer
36 views

How to add the values of a common field to a field during union

If I have say 3 overlay features; A,B,C each has a field called FIELD_ID If I do a union, I will get 3 new fields in the output: FIELD_ID_1, FIELD_ID_2, FIELD_ID_3 But how do I get just one ...
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1answer
92 views

How to do union that results to a SpatialPolygonDataFrame in R?

I have the following code coastline<-readOGR(dsn=".",layer="shp") wetlands<-readOGR(dsn=".",layer="shp") wetb<-gBuffer(wetlands,width=500,byid=T) wetb2<-gBuffer(wetlands,width=1000,byid=T)...
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49 views

Overlapping polygons with buffers and need to keep associated data [closed]

I have a point file that has been buffered by 400m. I have overlayed it on top of a polygon file and I need to keep all data that overlaps for each point. What is the best way to do this? I have ...
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28 views

Calculate normalized summary

I am trying to dissolve polygons having unique values for var1 and then calculate values for var2 to var4. Following is the attribute table. Var2 to Var3 values are dependent on the area. Dissolving ...
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1answer
32 views

Alphabetical Sort within a Record

I am performing a union on a polygon feature class with multiple overlapping polygons. Each of the records in the resulting feature class can be thought of as "unique area" polygons made up of the ...
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1answer
565 views

How to create a JTS geometry with holes and islands?

I have a JTS multipolygon geometry created by an Polygon array: multipolygon = gf.createMultiPolygon(this.polygons.toArray(new Polygon[this.polygons.size()])); Those polygons can describe holes or ...
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5answers
488 views

Easy way to sum up a lot of values?

I've got a shapefile that was made by the mother of all Unions. Because of that, it's got about 400 columns, and I want to sum about 100 of them (specifically, the "Score" from each). Is there an ...
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0answers
131 views

GDAL equivalent to ArcGIS Union?

I have a single shapefile full of overlapping polygons. The ArcGIS Union tool will generate individual, non-overlapping polygons with that geometry. Is there a way to do this with GDAL/OGR or another ...
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1answer
60 views

Using union and area increases?

I have two layers … assume A and B … one is landuse and one is limit of that. The main reason to union these two layers is to calculate street. But my problem is after I union these two the area ...
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1answer
28 views

QGIS Grid Union Issues

I am trying to create a choropleth map of ice concentration over Lake Erie. I have data for all the lakes (I can clip it all at the end), which are in a point shape file. I have laid a grid over the ...
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2answers
169 views

Shapely (geos) crashes during unary_union

When attempting to union multiple polygons with Shapely 1.5.6 in Python 2.7.9, using GEOS 3.4.2, I get the following error in the underlying C++ code: Assertion failed: (!"should never be reached"), ...
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1answer
636 views

postgis: cluster/group points based on distance

We have a set of thousands of points and want to group all of those which are within 100m distance from each other (to get the centroid from each group). A first idea was to build 100m buffers around ...
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2answers
84 views

Sum attribute in overlapping polygons

I have a month's worth of snowfall contoured polygons in one feature class. Polygons represent one day and has a field called SNOWFALL. How can I display the total snowfall for the month? I have the ...
2
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0answers
79 views

How to union linestring data distributed on multiple layers?

I have four shapefiles. Each contains a linestring as shown in the image. Each shapefile is represented as its own layer in QGIS. I would like to union these linestrings into one polygon which ...
6
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2answers
554 views

PostGIS ST_Union Performance

I'm trying to execute a 'dissolve' operation in PostGIS using the ST_Union command. The input layer is admittedly quite large and complex. By 'large' I mean 57,771 features, with number of vertices ...
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1answer
59 views

creating a new layer based on colour characteristics

I have 14 polygon layers. I have plotted them as transparent layers, so I can get a final layer with 6 different colours, which represent different categories. I want to create a new layer made by the ...
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1answer
73 views

arcpy Union w/No_Gaps puts “0” into blank fields

wanted to overlay two file geodatabase-based featureclasses where one has a smaller extent than the other, but preserve all input features in the output. I used arcpy.Union_analysis. In order to ...
2
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1answer
86 views

Is this Intersect or Union algorithm associative?

Similar to Is the Intersection Operation Commutative? . Spoiler for that one: Intersection is commutative and associative. I've created an algorithm (in PostGIS but the theory would work in other ...
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0answers
858 views

PostGIS: Merge any and all adjacent polygons

I would like to do adjacency tests on a parcel (polygons) layer and merge them if they fit certain criteria (could be size). Per the picture below, I would like to merge polygons 1,2,3 and 4, but not ...
3
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1answer
89 views

Unexpected vertices from the ouput of ArcGIS union tool

I have found some unexpected behavior of ArcGIS union tool. My assumption was that this tool will never add any new vertex to the output layer, but this was not the case. I have run the ArcGIS union ...
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603 views

How to perform a weighted overlay analysis with categorical classed data?

I have several land use layers (vector polygons) that all contain a field about land use in different classification systems and would like to combine them to a single classification. I would like to ...
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1answer
1k views

GEOS_ERROR: TopologyException: Input geom 1 is invalid: Self-intersection at or near point

I'm using GeoDjango (but I guess this is from the geos library). I have a set of polygons that compose a city surface and I want to merge them into a single one. The code looks like this: polygons = ...
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1answer
1k views

Intersect/union two different polygon layers to produce a third polygon type

Can anyone instruct me on the correct way to union/intersect two different layers containing polygons so that a third layer is created containing the attributes of the non-overlapping regions from ...