A "difference" operation is an geoprocessioning 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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Help Needed with QGIS Vector->Geoprocessing Tools->Difference [duplicate]

I'm trying to use the Vector Geo processing 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 - ...
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51 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 ...
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47 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.
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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 ...
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1answer
196 views

Graphically depict statistical difference between thematic rasters

The graph shows a regression between two raster datasets with classified tree canopy cover: class 1 = 0-10%, class 2 = 10 - 20% ...class 6 = >60% (Figure 1, Figure 2). The spatial resolution for ...
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48 views

How to subtract lines with thickness from polygon

I have a polygon and some lines crossing it. I want to subtract the lines with a certain "thickness" from the polygon, so it splits up into various polygons which do not touch each other anymore. You ...
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257 views

OpenLayers rules and context, what is the difference?

OpenLayers.Style employs two properties, "rule" and "context" which accordingly contain an array of OpenLayers.Rule and a set of methods. I have noticed that "context" can somehow substitute "rule". ...
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2answers
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A python tool like GNU's diff for shapefiles?

I often use the GNU diff tool to compare two files or even two folders for differences. I was wondering if there is a Python based tool out there that does basically the same for shapefiles? In the ...
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769 views

Raster vs Grid vs Lattice terminology?

I have a question about GIS terminology - what is the difference between grid and raster and grid and lattice - in theory?? I thought, that raster is regular network and value is in the cell and the ...
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220 views

Difference between Geographic and Projected coordinate systems?

What is the difference between a geographic coordinate system and a projected coordinate system?
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2answers
127 views

What is the difference between mosaicking and merging?

What is the difference betweem image Mosaicking and Merging?
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What is primary difference between ArcGIS for Desktop and ArcGIS for Server?

What is the primary difference between ArcGIS for Desktop and ArcGIS for Server?
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Analyzing differences between two shapefiles to put results into new shapefile?

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 ...