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.

learn more… | top users | synonyms

1
vote
0answers
22 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 ...
0
votes
0answers
33 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 = ...
0
votes
1answer
19 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 ...
0
votes
0answers
52 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 ...
0
votes
1answer
21 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 ...
1
vote
1answer
34 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 ...
1
vote
0answers
56 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 ...
0
votes
0answers
43 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 ...
3
votes
1answer
104 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 ...
1
vote
1answer
71 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 ...
0
votes
1answer
37 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?
0
votes
1answer
36 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 ...
1
vote
1answer
38 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 ...
1
vote
0answers
31 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 ...
0
votes
0answers
65 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 ...
1
vote
1answer
58 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 ...
3
votes
0answers
97 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 ...
2
votes
1answer
66 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 ...
3
votes
1answer
174 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 ...
1
vote
1answer
32 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 ...
0
votes
1answer
75 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) ...
1
vote
0answers
47 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 ...
0
votes
0answers
27 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 ...
2
votes
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 ...
2
votes
1answer
411 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 ...
3
votes
5answers
424 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 ...
2
votes
0answers
113 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 ...
1
vote
1answer
56 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 ...
0
votes
1answer
25 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 ...
1
vote
2answers
154 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"), ...
4
votes
1answer
591 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 ...
0
votes
2answers
71 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
votes
0answers
73 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
votes
2answers
482 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 ...
0
votes
1answer
54 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 ...
0
votes
1answer
64 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
votes
1answer
75 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 ...
5
votes
0answers
744 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
votes
1answer
88 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 ...
1
vote
0answers
488 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 ...
2
votes
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 = ...
1
vote
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 ...
3
votes
4answers
555 views

Is there a union function for multiple layers comparable to ArcGIS in open source GIS like QGIS?

I need a union function for a lot of polygon layers (protected areas of all kind, nature, water etc.) comparable to the union function in ArcGIS. I have only the desktop version from ArcGIS and so it ...
2
votes
0answers
148 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 ...
6
votes
1answer
301 views

PostGIS “Overlay” Style Union, not “Dissolve” Style [duplicate]

I'm trying to use PostGIS to do a 'union' of polygons. When I Googled "PostGIS Union", I found the ST_Union function, which performs what I would call a 'dissolve,' not a Union. What I actually want ...
-1
votes
1answer
677 views

Problem with running Union Tool - Error Code 000229

I have been working through an ESRI Tutorial for GIS Analysis. One of the tasks is to Union two feature classes (Flood Areas and Land Use) which are both polygon feature classes. Each time I attempt ...
1
vote
1answer
62 views

Union with Concatenated Values

I have a polygon feature class in which the polygons frequently overlap each other. I want to find all of the unique combinations of overlapping polygons within that feature class. I believe I want to ...
0
votes
1answer
223 views

How to union polygons and add attribute values of combined output features

I have a layer containing 10 polygons all overlapping at various locations. Each polygon has a value of '1' in a column called "value" How do I Union the polygons (rows) together such that the ...
2
votes
0answers
342 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 ...
0
votes
1answer
657 views

Using Union on multiple shapefiles to output single result

Using QGIS 2.2 and Python, I would like to use the Union algorithm on multiple shapefiles (contained in a folder TEST) which would then produce single shapefile containing all the data. Currently ...