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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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 ...
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507 views

SQL Server UNion of geography feature returns FULLGLOBE result?

I have some trouble with sql server 2012. I store coordinates of french cities in my database as geography object (with ESRI 4326) and i want to make the UNION of some cities. I have in result (...
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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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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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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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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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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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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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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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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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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 ...
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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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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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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 ...
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164 views

List of vector to one raster in PostGIS

Hi PostGIS developers! I need to rasterize a part of OSM map by coordinates. I found rather good algorithm, but can’t finish it. I have problems in STEP 3. I described all algorithm here – may be ...
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357 views

How can you calculate the union/merge two polygons in ogr2ogr?

I want to calculate the union/merge two overlapping polygons using ogr2ogr (as I have 300+ to do). I want the output to be the same as you would get if you used the 'Merge shapefiles to one' command ...
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35 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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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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83 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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600 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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16 views

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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16 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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49 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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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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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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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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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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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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289 views

Need advice on converting large geodatabase into shapefile or postgis

tl;dr: I have a fgdb w/ 800k tiny polygons representing high risk flood areas. I need to sum the area of these polygons within each administrative boundary (HUCs) and have a ratio per huc of high risk ...