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Questions tagged [dissolve]

To merge features based on specified attributes.

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30
votes
5answers
37k views

Fixing geometry validity errors in QGIS?

I am working on ownership data at a US county level. I have one shapefile per county that contains thousands of tax parcels. I need to dissolve the polygons representing parcels owned by the same ...
6
votes
4answers
7k views

Dissolving ploygons in QGIS or Grass to new polygons of defined population sizes?

I have a shapefile with 3800 polygons representing the smallest administrative areas in Ireland. Many of these, in rural areas, have tiny populations, under 100 people. In urban areas, all would have ...
22
votes
3answers
58k views

Merging/Dissolving polygons by Common Attribute Field in QGIS?

I have joined corresponding Local Enterprise Partnerships table data into a polygon shapefile containing UK Local Authorities. How do I Dissolve or Merge the the Local Authorities polygons by ...
47
votes
4answers
35k views

Joining lots of small polygons to form larger polygon using PostGIS?

I have the following layer using SRID 27700 in postgis: It's every administrative region in the UK, and (as you can see from the colour grouping) each of them has a text field specifying the county ...
24
votes
1answer
19k views

Merging adjacent polygons in shapefile that has been split at tile boundaries?

I'm currently using building data from the Ordnance Survey Vectormap District and I've noticed that a lot of building polygons are split in 2 because of the way the OS split up the shapefile. This is ...
7
votes
4answers
4k views

Unsplit/Dissolve multiple touching lines in Stream Network using ArcGIS Desktop?

I am trying to dissolve multiple lines for stream networks into individual features. The dataset contains many stream networks so a complete dissolve of the whole dataset wont do as I would like to ...
21
votes
3answers
18k views

Is there a dissolve function in PostGIS other than st_union?

I'm looking for a function to dissolve shared boundaries between polygon features in a table. ST_UNION() almost does what I'm looking for, but it creates a multipolygon from all polygons in the layer ...
3
votes
2answers
3k views

Batch Dissolve Polygons based on Attributes in QGIS or FWTools

I was wondering if anyone can help with batching a dissolve. I have a few hundred polygon shapefiles that I want to dissolve based on an attribute. I would like to do this in QGIS or FWTools.
7
votes
4answers
3k views

Improving upon ArcGIS Buffer/Dissolve performance?

I'm wondering if anyone else has experienced significant performance penalties when using the ArcGIS buffer function with the 'dissolve' option on point features. My dataset is a shapefile of 260 ...
11
votes
2answers
10k views

Dissolve polygons in QGIS (GEOS) with tolerance

I have a polygon vector layer representing the area inundated in a flood. The layer has been produced in a such a way that some of the areas are composed of multiple smaller touching polygons (see ...
7
votes
1answer
1k views

Cleaning large Shapefile using v.clean in order to dissolve features?

I'm having real problems cleaning up and reducing the size of a Shapefile which is published by the UK's Environment Agency. It shows the extents of the LiDAR open data they publish: each polygon is ...
4
votes
4answers
7k views

Why is the Dissolve Tool not working?

I'm still having trouble with the dissolve tool and I've tried all of the solutions offered here including moving the process from the background and repairing the geography. I've also tried amending ...
3
votes
2answers
2k views

Cleaning polygon after using dissolve to repair geometry in QGIS?

I'm trying to obtain the boundaries of shapefile, thus to clean the inside as a matter of speaking. While I had expected that dissolve while get me a proper polygon, unfortunately it still has some ...
4
votes
1answer
184 views

QChainage doesn't place points evenly along dissolved lines

I am trying to add mile markers to interstate centerline data. I've tried both the native dissolve tool (which freezes QGis) and SAGA line dissolve to create one continuous line. When I run the ...
3
votes
1answer
1k views

Merging lines with same name and intersect each other?

I have shp file with 50k lines (roads). Many roads have same name like 'high road' . some of them are the same road (they intersect each other) and some are located in different places of the city. I ...
9
votes
4answers
14k views

Dissolve not working in ArcGIS 10

The dissolve tool is not working for me when I use ArcGIS 10. It works perfectly when I use version 9.3. Any help?
9
votes
2answers
34k views

Combining adjacent polygons sharing similar trait into single polygon using ArcGIS Desktop?

I have a large dataset of habitat classes which I have further simplified down into my own unique classes. However, it resulted in there being habitats adjacent to each other with the same forest ...
8
votes
1answer
1k views

Deleting 'garbage' nodes after polygon dissolve [duplicate]

I work with QGIS 2.10.1 on Windows 7 (x64). I have dissolved polygons from an attribute value and the polygons geometries being not perfectly joined together, I get some 'garbage' nodes I need to ...
7
votes
1answer
4k views

PostGIS Dissolve/Union close polygons

I have approximately 1 million polygons that have been split by lines. However, this has caused one half of a polygon to be separated by approximately 50cm from its other half. After doing a lot of ...
6
votes
1answer
5k views

“Singleparts to multipart” vs. “Dissolve”

It seems to me that the vector tools "Singleparts to multipart" and "Dissolve" do the same things. Can someone confirm this, please? Or do I overlook something?
5
votes
1answer
1k views

Dissolve only overlapping polygons in R

I have a spatialpolygons-dataframe in R that contains overlapping polygon features. I would like to dissolve only the overlapping features into separate polygon features (one feature per par of ...
14
votes
3answers
8k views

ArcGIS Desktop tool that does for records in a table what “Dissolve” does for features?

I have a data table that I need to trim down, merging records which have the same value in an ID field and performing a couple math operations on various other fields (summing, averaging). The ...
6
votes
6answers
2k views

Dissolving polygons fails on computers with small amount of RAM

When I'm trying to dissolve a polygon through an arcpy script the operation fails with the 999999 error on computers with small amount of RAM [~3 GB] (known issue). Unfortunately neither: arcpy....
3
votes
1answer
425 views

QGIS 2.4.0: dissolve tool renders artifacts / errors

The dissolve tool (vector>geoprocessing tools>dissolve) renders some artifacts on shapes with high number of polygons. I’m using a shapefile with 3222 polygons and I’m trying to dissolve it using the ...
10
votes
3answers
42k views

How to dissolve overlapping polygons?

I have a query regarding the dissolving of polygon features in ArcGIS 9.3. I only have the bare-bones license and an extremely basic knowledge of VB. I have a large shapefile with around 4500 ...
11
votes
3answers
30k views

Merging adjacent polygons using ArcGIS Desktop?

I want to use ArcGIS Desktop to merge adjacent polygons with each other. There is no common field between the polygons and hence the Dissolve tool is not the ideal solution. The polygons that I want ...
9
votes
1answer
8k views

Dissolving shapefile but retain attribute fields using ArcGIS Desktop?

Is there any way to dissolve shapefile but keep attributes fields in the same time? This is how I want to retain fields: There are two fields I want to conserve in a shapefile. The first column is ...
7
votes
1answer
639 views

Dissolving shapefile but retaining a list of original attribute value in QGIS

How can I dissolve a polygon layer in QGIS based on a single attribute but keep all (or some) other attributes at the same time? This is how I want to retain fields: There are at least two fields I ...
4
votes
4answers
1k views

QGIS classifying vector data

I am trying to classify a shapefile based on rule set, following this tutorial. This is the result: What I want to ask is: 1. How to insert the classification result (water, land etc) into the ...
7
votes
0answers
214 views

How do I select the longest connected lines from PostGIS ST_ApproximateMedialAxis?

I used PostGIS ST_ApproximateMedialAxis to transform polygons representing mountain ranges into a series of lines. Now, I'd like to select only the "longest" line segment for each group, so that I ...
4
votes
1answer
1k views

Group and union polygons that share a border in R

I am attempting to union all polygons that: 1) share any portion of a border, or 2) have within a certain threshold distance (e.g., 50m) of each other, within a SpatialPolygons object. for_cov_sp_0 ...
2
votes
1answer
1k views

Assigning overlapping polygons based on attribute using ArcGIS for Desktop?

I am using ArcGIS 10.1 and have a polygon shapefile with 16000 records. There are many polygons that are overlapping and my goal is to determine the overlap portions fix the problem, so that there is ...
11
votes
1answer
4k views

How to achieve equivalent to Dissolve from ArcGIS for Desktop using ST_Union?

I am trying to achieve an equivalent to the Dissolve tool from ArcGIS for Desktop using ST_Union from PostGIS but it seems I am not getting expected result. I have one table which has certain ...
5
votes
3answers
754 views

Dissolve overlapping polygons in SAGA

I've got the following (2D!) situation of overlapping polygons: I would like to have the polygon border dissolved such that I have only one polygon left. I thought this was a definitive case for the ...
4
votes
1answer
370 views

Dissolving reprojected features split into two parts by international dateline (180 degrees) in QGIS

I am trying to view the World EEZ polygon from Marine Regions.org, but centered on the Pacific Ocean. To centre the EEZ map on the Pacific ocean I followed these steps. The custom CRS from this ...
4
votes
2answers
820 views

Dissolving by two fields in QGIS?

Is there a way in QGIS to dissolve a vector by two or more fields?
3
votes
2answers
2k views

Stratified Random Sampling with large dataset in ArcGIS?

I want to create a Stratified Random Sample with a land cover classification map. The purpose for the Stratrified Random Sample is to produce an Accuracy Assessment. I am using ArcGIS 10.2 with access ...
3
votes
3answers
1k views

Concatenate fields on a Dissolve

I have a feature class that that I would like to dissolve. Upon the dissolve, I would like to concatenate a comment field, which is a text field. How can I do this? Conceptual idea below:
2
votes
1answer
4k views

Dissolve features in ArcGIS using multiple attributes

This may sound simple, apologies if I missed some earlier discussion on same subject. I have a big set of road data with road numbers and also zone numbers . The road names can repeat across the ...
2
votes
3answers
915 views

Buffer and union of large shapefile?

I want to create a buffer of 5km around the coastline, and save that as a separate shapefile. I have a shapefile with almost 180,000 features. It's a line shapefile, representing the coastlines of ...
2
votes
2answers
558 views

Seeking ArcPy dissolve to multipart workaround for when arcpy.Dissolve fails [closed]

I have an ArcPy script in which I am using arcpy.Dissolve on a single feature class with multiple features to get a single multi-part feature in the output. The script is successful only part of the ...
8
votes
1answer
2k views

How to create point labels from midpoints of road polylines in QGIS?

I have a road polyline layer (singlepart ie has several features per road, grouped by an id field), and i want to (after merging the parts) find the mid point of the resulting lines. This is for roads ...
3
votes
1answer
391 views

How to achieve better Dissolve results?

I applied the Vector>Geoverarbeitungswerkzeuge>Auflösen (Dissolve) on a zoning plan (see picture zoning plan). I used the attribute village name as the dissolving criteria. The resulting geometry for ...
3
votes
1answer
110 views

Assigning common field value to segments between two points using ArcGIS for Desktop?

I am using ArcGIS 10.3 for Desktop. I have a shapefile with polylines connecting points. Instead of having one single polyline connecting two points, there exist a number of consecutive segments ...
3
votes
2answers
796 views

Avoiding/getting rid of topological errors after dissolve?

After dissolving a layer in QGIS 2.8, I get a lot of topological errors in the new (dissolved) layer. Any suggestions as to how to get rid of these errors without manually editing each one? update: ...
3
votes
2answers
3k views

Dissolving line segments in QGIS if they touch and fall within same class?

I have line segments that have the following 3 attributes (Class, start_point, end_point). I would like to merge/dissolve line segments that fall within the same class if they intersect (touch). i.e. ...
3
votes
1answer
1k views

Dissolving only selected features in a layer?

I am curious to know if it is possible to dissolve only the selected features in a layer in QGIS. In ArcGIS this is the default behaviour (which was actually someone annoying most of the time), but ...
2
votes
3answers
2k views

Dissolve polygons - group to others with touching corners

I am working with some data that shows land management. There are many places where corners "touch". I would like to dissolve my dataset so that features are grouped (dissolved) with those that they ...
2
votes
1answer
934 views

Dissolve overlapping polygons in R

Is there an analogue of ArcGIS Dissolve function in R? I need to dissolve the overlapping polygons and create a single part object. I was trying to use gUnionCascaded, but it creates a multipart ...
2
votes
3answers
34k views

How to combine rows in attribute table using ArcGIS for Desktop?

I have an attribute table with three columns "FID" "Shape" and "Class" All records have the same shape (polygon). Each record has its own FID. I have three classes, "A", "B", or "C". I have twenty ...