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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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22 views

Algorithm “qgis:difference” returns multiple heterogeneous outputs

I use the qgis:difference algorithm but it returns multi-type outputs. Sometimes it's a QgsVectorLayer but sometimes a str such as : output_.... My question is : when the algorithm returns an empty ...
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1answer
27 views

Extracting difference between two shapefiles (not symmetrical difference) using ArcGIS Desktop?

I have a shapefile with polygons that portray survey areas (Pink areas in picture below). I receive a new updated shapefile with additional survey areas, and thus new polygons (Green areas in ...
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22 views

Erros in the elevation model differences [closed]

I have two DSM (one is before a landslide, and the other is after) with a spatial resolution of 10 m x 10 m in horizontal and 1 m in vertical. I subtract one from the other to get the difference in ...
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1answer
121 views

Vector difference between two polygon layers by attribute

Is there a way to do a 1:1 difference between two polygon layers based on a similar attribute? The layers have the same number of features with a shared attribute. I've tried the native QGIS ...
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148 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 ...
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0answers
34 views

How do I select rows in an attribute table of a vector layer grid which are outside of another vector layer?

So what I am working on is accessibility analysis, I want to know how many percent of the population of a country have access to certain health services within a given driving time. For example is it ...
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2answers
102 views

Difference between two polygons in Earth Engine

I have a reservoir and its buffer (see below). I want to do the difference between the 2 so that my buffer is just a contour around the polygon. I tried the 2 following scripts but cannot get the "...
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1answer
26 views

Using “Difference” geoprocessing tool on Big Data taking a very long time

I am using QGIS Bonn 3.2.3. I've recently been using the Difference function to calculate a list of points and it is taking a terribly long time. I was wondering if you could point out any obvious ...
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1answer
59 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....
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29 views

reverse clip (erase) for spatial point data frame (R) [duplicate]

I am trying to recreate the suggestion from this link but instead of using it on a sPolygondf, to do the same for a sPointdf. All is well, but I get an unexpected output - when I do the difference ...
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1answer
276 views

shapely.difference() possible bug or wierd behavior

So, by definition, if we have polygons A and B, A.difference(B) should return: 1) the same polygon if A does not intersect with B 2) the difference of A and B if they intersect 3) empty geometry if ...
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1answer
101 views

Style features based on difference between current date and date in attribute table

In QGIS >2.18, is it possible to style features based on the age gap between the current date and date recorded in the attribute table. For instance I have purchased a significant amount of OS data ...
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1answer
82 views

Area difference between polygon layers

I would like to calculate the difference of area between two polygons. I tried using the Difference tool, but all it does is create lines that are different between my two polygons. I also tried the ...
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0answers
149 views

Saga difference vector tool

My QGis Difference tool doesn't work really well, it gives me lots of little squigly lines. i read in the link below there is such a thing as a vector diffence tool from SAGA, but i can't find it. ...
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1answer
68 views

Splitting One Polygon By Boundary of Another using QGIS?

I'm using QGIS 3.0 and attempting to calculate the number of people that fall within a buffer. The population count is a field within my block group polygon layer. I've attached a screenshot, the ...
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1answer
112 views

Processing Problems with the Difference (QGIS) and Erase (ArcGIS) Tool with big data

I am struggling with processing a huge data set. I downloaded it from a German geodata site (https://download.geofabrik.de/europe/germany.html). I downloaded the ZIP of Bavaria and clipped the eight ...
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26 views

Methods to differentiate between terrain

I am not specialized in GIS. I have some moisture contour maps, I want to compare each pair to trace the changes between either in a numeric way. I tried to get the mathematical difference between ...
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1answer
334 views

Map statistical significance in the difference of two raster maps

I have two raster maps that are the output of the same model (they describe the same variable) but ran with different parameters and I would like to assess if there is a statistically significance ...
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2answers
258 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 ...
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0answers
277 views

Difference or Erase layer/shp from another layer using GDAL / OGR?

Gdal is known for being the fastest library for geospatial data processing. I'm using it in my python script and I'm having issues with performance on a specific task which is Erasing a layer from ...
3
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2answers
77 views

Duplicated Features in point layer

I have duplicated features in point layer (Land Marks) but these duplicate has 2 cases : they might be not all have their center above each other (some have it at center , some is a bit far but its ...
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1answer
286 views

Calculating between today's date and date field in attribute table ofArcGIS Desktop?

I am trying to use DateDiff to calculate the difference between today's date and the initiated date of various projects. I created a new field called "Duration of Day" and I tried the calculation: ...
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1answer
205 views

Count points not in polygon in QGIS (difference between points and layers give unexpected result)

I have a layer of 130 points and another layer of driving distances as 6 polygon features When I use the count points in polygons I get a running total of the number of points in each polygon feature (...
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1answer
54 views

Downloading kmz/shapefile of differences between 2 compared image dates from planet.com?

I'm interested in downloading a KMZ or shapefile of the difference feature when you compare days on planet.com. The images are huge composites so I don't think downloading 7,000 items for each date ...
4
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1answer
70 views

How to use the method makeDifference in the console?

I would like to do a "difference" between 2 features in PyQGIS. I don't understand how to use the method makeDifference() as shown on the documentation here. It says the parameter to pass the ...
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1answer
650 views

Difference between lines and polygons using geopandas

I wanted to geopandas.overlay() on lines and polygons : get the geometries from the lines that are not in the polygons. I tried using geopandas for this : result = gpd.overlay(my_lines, my_polygons, ...
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1answer
876 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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1answer
150 views

Subtract MultiPolygon table from LineString table

I've two tables, one with a roadnetwork and another one with some polygon. The roadnetwork table has a geometry column defined as COLUMN geom geometry(LineString,4326); while the polygon table has a ...
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1answer
378 views

Difference Tool (Polygon) Not Working

Okay so I'm using QGIS 2.10 (a couple of versions out of date, but shouldn't matter much, eh?) on Windows 7, and I can't figure out this supposedly a very basic geoprocessing tool DIFFERENCE. I'm ...
5
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1answer
361 views

Deleting sliver polygons after difference operation in QGIS?

I'm trying to 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, ...
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1answer
101 views

Removing duplicates in lines using PostGIS?

I have a new polyline and need to remove duplicating parts from it. New polyline is compared to other polylines stored in PostGIS table. I have a query that removes duplicates from line newTrack ...
4
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2answers
507 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. ...
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1answer
568 views

Trouble using ST_DIFFERENCE() function in PostGIS

If have this: CREATE TABLE buff as ( SELECT route_sutton.id, ST_BUFFER(route_sutton.geom, 30) as geom FROM route_sutton ) CREATE TABLE couvert_dif5 AS ( SELECT nextval('temp_id') AS id, ...
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0answers
626 views

Remove polygons of one layer from another polygon layer in QGIS

I have two polygon layers, A and B, both in the same projection. I am trying to create a new layer, C, which is all polygons in A less the areas where polygons in A and polygons in B intersect. I am ...
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1answer
74 views

How to use ST_Difference in case of an featureless input table?

I use the query posted below to create the difference of two polygon layers. CREATE VIEW public.v_diff AS SELECT row_number() over() AS gid, subquery.geom FROM (SELECT (ST_Dump(COALESCE(...
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2answers
900 views

How to compare 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' ...
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1answer
73 views

Comparing areas of overlapping shapes in QGIS

Given SHP files for a country's Districts in Year1 and Year2, how to output a table whose rows state the percentage composition of each Year2 District in terms of portions of Year1 Districts
3
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1answer
665 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 ...
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0answers
131 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 ...
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3answers
698 views

Creating rings from existing polygons using QGIS?

I have been given a shapefile from a client that features pivots, yet they were recorded as 10 circles overlapping. The software my company uses requires that these polygons be rings that don't ...
15
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3answers
848 views

How to create 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 ...
6
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2answers
407 views

How to use ST_Difference to create linestrings from non-intersecting polygon boundaries?

There are two tables with polygon features in my PostgreSQL database. I want to create linestring features where the boundries of the polygons are not intersecting. CREATE TABLE schema.poly_a ( gid ...
5
votes
2answers
970 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 ...
3
votes
1answer
83 views

Vector differencing fails in QGIS (due to geometric errors)

I was trying to correct the country shapefile of Uzbekistan for Gas flares: Input layer (the UZB_adm1) differenced by this layer. In QGIS the result was that the overlapping regions - where the ...
2
votes
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 ...
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2answers
118 views

Viewing results of ST_Difference

I've got an ST_Difference query runnning error free in PostGIS, and in PGAdmin I can see the output table but it's not viewable in QGIS - The table name appears in DB Manager but says "There is no ...
2
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1answer
436 views

Calculating area using dissolve and merge but getting shapefiles with empty attribute tables in QGIS?

I have a shapefile of a country with the 29 provinces. I also have shapefiles with the areas which are protected from construction (there are 4 categories for protection, within 4 shapefiles. Some of ...
2
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0answers
164 views

Using QGIS Vector->Geoprocessing Tools->Difference? [duplicate]

I'm trying to use the Vector Geoprocessing Difference Tool in QGIS to "take a bite" out of one polygon using another in another layer. The tool menu Difference icon is exactly what I'm trying to do - ...
5
votes
1answer
920 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 ...
3
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2answers
1k views

How can I eliminate leftover border/boundary in QGIS?

I am trying to generate a shapefile which contains the unincorporated areas of St. Louis County, Missouri. I'm using two shapefiles: St. Louis County from the 2012 census, followed by St. Louis ...