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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Difference tool failing for QGIS map layers

I had tried to run the 'Difference algorithm' on two layers. However, the process constantly fails with a "GEOS geoprocessing error: difference failed" message. When I tried running an ...
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1answer
80 views

Getting the 'composite' of two polygon layers

I have two table of polygons, and I want to 'flatten' them into one table, and have the result tell me which areas are in one table of polygons, which in the other table of polygons, and which are in ...
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QGIS Difference Algorithm: multilinestring won't work with multipolygon layer

I am working with two vector layers in QGIS (location: Indonesia). I want to 'subtract' the area of layer 1 ('Forest_buffer') of layer 2 (Scenario_1). I am using the Difference algorithm. Layer 2 is ...
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1answer
58 views

Compare two layers and find the percentage of the shared areas that are different between them

I have two shapefiles that identify flood zones for the same general area but in different years. The maps, however, do not cover exactly the same geographical areas (e.g., shapefile 1 covers counties ...
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40 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 ...
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1answer
105 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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57 views

PostGIS: Using ST_CoveredBy (or similar) to speed up Difference on large datasets?

I need to get the Difference of a single large-area polygon (input layer) and a very numerous set of polygons (overlay layer). The overlay layer has ~500k polygons, of which ~200k intersect the input ...
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16 views

Difference between overlapping polygons using OGR

I’m trying to do a simple difference between two polygons using ogr, but I can’t make it work. The input layers have the same CRS. The input polygon is a multipolygon, and the overlay polygon is the ...
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41 views

QGIS v/s MapInfo - Differences in Distance Measurements

Distance calculated in different software (MapInfo and QGIS) has given me differences in distance values. To be more precise, it's mostly happening when the distance is more than 25 miles. I doubt ...
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1answer
36 views

Difference tool for rasters

I am using QGIS 3.16.0 and I need to find the difference between two rasters that overlap in some areas (basically I need the areas that are not overlapped). First, I tried polygonizing the smaller ...
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1answer
92 views

Select points outside of polygon in Google Earth Engine

I understand how to get the points that fall inside a polygon with GEE: // Load a feature collection and a area of interest var dataset1 = ee.FeatureCollection("link/to/any/point/dataset/on/gee&...
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2answers
895 views

GEOS geoprocessing error when using difference tool in QGIS

I am using QGIS version 3.14.0. I have about 20 polygon .shp-files with overlaps between files. All are in the same projection. I've been using the difference tool to remove the overlaps and then ...
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53 views

“difference” between two rasters using raster calculator QGIS

I am struggling to find the right equation to use in the raster calculator to achieve my desired result. Essentially, I have two rasters, with an overlapping portion. See img below: I want to only ...
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1answer
127 views

QGIS difference operation with XYZ tiles

I have a regular layer from a database containing WKT polygons. I'm also using a XYZ Tiles layer of Google Maps. I would like to perform the Vector > Geoprocessing Tools > Difference operation ...
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146 views

Symmetrical Difference using fiona and shapely

I have a polygon that I want to merge into an existing polygon. To do this I first need to run symmetrical difference between the two overlapping polygons, and then merge them. Before symmetrical ...
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2answers
94 views

Difference between two features in same polygon in QGIS

I have a polygon and some features are below another features. If I would have two different polygons I would use the "Difference" tool so it would take the overlapping feauters to the "...
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1answer
130 views

Difference in geometries of shapefiles

I have the geometry of the outline region as part of one shapefile (which is only one feature and there are other features in it apart from this). Other polygon regions' boundaries which are colored ...
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1answer
111 views

Using QGIS Difference with Point and Polygon

After installing a fresh QGIS 3.10 version on a Windows computer I recently saw an unexpected behavior of the "Difference" feature from QGIS. (on one of my old computer with QGIS 3.4 it is different) ...
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1answer
166 views

Calculate difference of two LineString

The tool I'm developing is written in Java with Spring Boot, using PostgreSQL as database (PostGIS extension). I also make use of GeoTools. I want to calculate the geometrical difference between two ...
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34 views

Difference tool QGIS shows too many Differences

After running QGIS Difference Tool, I get a lot of differences, but I don't know where they are coming from. The input files are almost similar... Input Image (overlay input almost the same, but from ...
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1answer
93 views

Finding differences between polygons in PostGIS

I have another redistricting question. The datasets and queries available on my GitHub, but I will include the queries here, too. I am working on two complete datasets: 1) A PLAN - composed of ...
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1answer
76 views

How can I process vector difference between 1 group layer and 1 polygon layer?

I have one layer group called 'left_buffer', containing 40 buffered polygon layers (name: 1,2,3,...,39,40). I want to use difference vector tool between 'left_buffer' and 'bldg' layer, but I'm getting ...
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Inaccurate difference operations in GEOS

I've noticed large inaccuracies in the Django GEOS API's difference operation, see the example below. In [3]: geom1 = GEOSGeometry('{ "type": "Polygon", "coordinates": [ [ [ -19.51171875, 37....
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2answers
108 views

PyQgis difference iteration

I use Qgis. I have two layers that are two circles with the same center. One larger and one smaller. I want to do the difference between the two circles BUT only if they have the same "objectid" (the ...
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2answers
418 views

Doing difference between two layers in PyQGIS?

I'm developing a plugin where I would like to get some features from one layer (a), do a difference on them with the entirety of a second layer (b), and put the results into a layer I've created in ...
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1answer
130 views

Quicker function than dissolve and difference

I'm on QGIS (v. 3.6) trying to create a map of Florida's hydrography using the NHD "Water Areas" shapefile. Methodology is to fix any invalid geometries in the NHD data, dissolve the layer, and then ...
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36 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
209 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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1answer
2k 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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1answer
2k 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
49 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
548 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
136 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
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....
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115 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
2k 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
295 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
134 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
338 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
144 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
340 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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30 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
619 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
609 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
569 views

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

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
89 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
641 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
446 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
66 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 ...
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1answer
111 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 ...