Questions tagged [st-union]
The st-union tag has no usage guidance.
12
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How to Append a POINT to a MULTIPOINT column
I have a table in postgresql that includes a geometry(MultiPoint,4326) column.
I want to run a process that appends a new MULTIPOINT(4.49306 52.26167) to this column. I am currently doing this:
UPDATE ...
- 161
1
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2
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149
views
PostGIS ST_Union using array of geometries
I'm new to PostGIS and I have a set of layers that need to be merged and dissolved. I have no problem doing this for 2 input layers using ST_Union(geometry g1, geometry g2), but for more than 2 layers,...
- 41
1
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1
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207
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Dissolve/Union large number (1.2m ) polygons in PostGIS
I am very new to PostGIS. I read that it should work faster than QGIS, so I thought I'd give it a go. I want to completely dissolve a shapefile of 1.2m polygons in the same way as QGIS built in ...
- 511
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0
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37
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Visualise results from STUnion in SQL-Server 2008 R2
I have an SQL table which contains the buffers polygons of points. These buffers should now be aggregated any displayed as a single Polygon/Multipolygon. With the following command I think I can do a ...
- 10.2k
3
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2
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351
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using st_collect vs st_union to calculate centroids
Here is my code:
SELECT cluster_id, st_centroid(st_union(points_geom)) as cluster_centroid
FROM clustering
GROUP by cluster_id
Should I replace st_union with st_collect? Because the coordinates for ...
- 839
2
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1
answer
63
views
Postgis dissolve boundaries and calculate mean values
I like to combine two layers and calculate/summarize data from one to another. So, I have values for the subtypes (yellow lines) and the area of the subtypes. Now I like to calculate a mean value for ...
- 725
3
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1
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376
views
How do I optimize a spatial query in PostGIS
I'm trying to speed up my query which should return only these polygons that are not completly overlapped by polygons above them.
My tables looks like this:
Map -> Layer -> Object
The object ...
- 437
1
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1
answer
425
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ST_Union in Apache Sedona
I'm trying to merge some polygons with ST_Union using Apache Sedona on a databricks cluster.
%sql
SELECT Polygon_Name
,ST_Union(Polygon_Boundary) AS Polygon2_Boundary
FROM tbl_polygon
GROUP BY ...
5
votes
1
answer
902
views
Unsplitting/merging lines that have coincident endpoints using PostGIS
I have a large dataset of lines/linestrings (ie. a road network), which is unregularly segmentised/ split and the lines needs to be merged at coincident endpoints (if only two lines are touching). I'd ...
- 163
5
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1
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1k
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Counting geometries which intersect another geometry using PostGIS
I'm trying to calculate the total area for each layer I have within a specific area and count the geometries which intersects with that specific area.
I can calculate the area and the results seem ...
- 437
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153
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Virtual layers w/ spatial query not working as before (3.18.1 vs 3.20.3)
I have a set of maps that intensively utilizes virtual layers, but last week our boss updated from QGis 3.10/3.18 to 3.20.3 in all PCs, and now the layers are not loading.
Normally they would refresh ...
- 363
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1
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463
views
Using ST_Union to aggregate polygon parts resulting of ST_SubDivide leads to a GEOS TopologyException
Follow up on this topic: Optimizing an intersection between a single massive multipolygon (WKT) and many features from PostGIS
I noticed I have to run an ANALYZE (not VACUUM ANALYZE!) on the table for ...
- 9,776