Questions tagged [differences]

A "difference" operation is a geoprocessing operation that completely removes one overlapping polygon and the intersection of that polygon from the other. It uses one polygon to "take a bite" out of another.

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3
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1answer
134 views

Using PostGIS to find the overall difference between two (large) polygon datasets

I need to get the Difference of an input layer with ~30k polygons and an overlay layer with ~500k polygons (of which ~200k intersect the input layer). I am trying to learn PostGIS to do this, as it ...
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3answers
2k views

Can ogr2ogr "reverse clip" (or "clip out" or "erase" or "difference") one shapefile from another?

Is there a means in ogr2ogr to "clip out" one shapefile from another? I know ogr2ogr -clipsrc B.shp out.shp A.shp will remove any part of A.shp that is NOT in B.shp. Is there an ogr2ogr command to ...
15
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3answers
1k views

Creating lines to visualize differences between polygon features in PostGIS

I've a PostGIS table polygon_b with some polygon features. There is also a table polygon_a which contains the same polygons as polygon_b but with minor changes. Now I want to create lines to visualize ...
10
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3answers
25k views

Analyzing differences between two shapefiles to put results into new shapefile using ArcMap

I have two polygon shapefiles of the same region from two different years (1985 and 1997) and I need to analyse the differences between the two shapefiles resulting in a third polygon shapefile ...
12
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1answer
14k views

Distinction between Difference and Clip tools in QGIS?

What is the primary distinction between the Difference and Clip geoprocessing tools in QGIS?
5
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1answer
14k views

Difference between Geographic and Projected coordinate systems?

What is the difference between a geographic coordinate system and a projected coordinate system?
10
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5answers
5k views

Raster diff: how to check if images have identical values?

Is there a means to check to see if any 2 given raster layers have identical content? We have a problem on our corporate shared storage volume: it's now so big that it takes over 3 days to conduct a ...
6
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2answers
1k views

Comparing polygon boundaries in PostGIS

I've to compare two polygon layers, 'land_use' and 'land_parcels', in PostGIS. My aim is to create linestrings, where boundaries of 'land_use' polygons do not match boundaries of 'land_parcel' ...
6
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1answer
3k views

Function in R to get difference between two sets of polygons comparable in speed to QGIS

I have two very large polygon shapefiles for which I need to calculate the difference between the two shapefiles. One is a shapefile of forest polygons, the other is a shapefile of road polygons. I ...
6
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1answer
643 views

Deleting sliver polygons after difference operation in QGIS

How do I find the differing polygons between two layers in QGIS? After running the difference operation, however, I get results like this: I am only interested in the solid (blue) polygons, not the ...
5
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2answers
2k views

Clip polygon using buffer

I'm very new to QGIS, so apologies if this is a daft question. I've been trying to resolve my problem for a couple of days and I can't get anywhere. I have searched for similar issues here on SE but ...
4
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2answers
1k views

QGIS Difference not working?

I'm trying to simply get the Difference between two sets of lines, but the algorithm returns a copy of either one, depending of the combination of INPUT/DIFFERENCE layer I try. Never the difference. ...
3
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1answer
2k views

Comparing two shapefiles(layers) and display the differences in features in MapContent object in GeoTools

I am working with GeoTools libraries to implement GIS features. Here, I have two different shapefiles and I want to generate a new separate layer containing the differences between the two shape files....
3
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1answer
880 views

Whats wrong with the difference tool QGIS 2.14.1?

I want to get the difference between two poligons. I compare the result from Arcgis erase tool and QGIS difference. ArcGIS give me that I want, but Qgis don't. Why? QGIS not only give wrong ...
2
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0answers
194 views

QGIS difference output has same number of features

Having a problem with the QGIS Difference feature. Two inputs: a point and a polygon file. I am trying to generate a list of the points that are not covered by the polygons. I am using the "use only ...
2
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1answer
2k views

QGIS 'Difference' tool return empty layers

I've been using QGIS's difference tool to create some new layers. All was going well until I hit a number of layers which return a blank layer with no features when I use the difference tool. The ...
2
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2answers
3k views

How to erase polygon from another in QGIS

I want to erase the pink polygon from the blue polygon. I've tried clip, difference, and symmetrical difference. Clip produces an empty polygon. Difference produces just another blue polygon.
2
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1answer
2k views

Difference Between Polygon Layers

I'm trying to get the difference between two polygon layers using the QGIS difference function. These are the two files: Dropbox When I view the attribute tables of both I can see there are 3 ...
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0answers
49 views

PostGIS - ST_Difference creates extra line segment

I have some line of sights from one point, collected into a multilinestring. I want to cut the multilinestring using PostGIS' ST_Difference and a border-dataset (a single multipolygon). I used this ...
1
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2answers
65 views

"Difference failed" error when using difference tool with point layers as input and overlay in QGIS

Is it possible in QGIS 3.16 to use the geoprocessing tool "Difference" with point layers as input and overlay? The documentation seems to indicate that it is. However, when I do a test with ...
1
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2answers
661 views

Points and polygons difference issue QGIS

I'm trying to remove points that are in polygons with the basic difference tool (Vector-> Difference). What I see after the operation suits me because all points in polygons are deleted, but as I ...