The process of producing a polygon feature layer from a raster or from lines.

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6
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1answer
239 views

How to extract vectors from map using QGIS?

I am trying to extract building footprints from a raster map (as shown in the example below). Please note that the maps are out of copyright, have been scanned and georectified by a library and have ...
1
vote
1answer
30 views

How to crop a vector shapefile according to raster?

I am trying to clip a vector shapefile- points according to a DEM in QGIS. I used GDAL function and polygonized the DEM. Then I ran the Vector-Geoprocessing tools-clip in order to crop the vector data ...
0
votes
1answer
280 views

Polygonize.py: AttributeError: 'NoneType' object has no attribute 'CreateDataSource'

Given a topographic raster tif of an european country where elevations are simplyfied to either 0, either 200. How to create a polygon ? Comment: With the following polygonize.py command: ...
3
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0answers
375 views

GDAL polygonize lines

I have a raster file containing roads (left image). I polygonize the raster file with GDAL (see the script below). In the end I like to have vector lines. However GDAL only gives me something like ...
3
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0answers
113 views

Why doesn't Polygonizer copy the line ids to my polygonized shapefile?

I am trying to convert a line shapefile into a polygon shapefile using Polygonizer plugin, and when my new polygons are created all the cells in my id field are "Null", although I have clicked "copy ...
2
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0answers
33 views

Error in polygonising raster data with QGIS on Mac

I'm using QGis Chugiak on a Mac and I'm trying to converting a raster layer in a vector data by: Raster/Conversion/Polygonize. So, I select the layer needed from the drop-down menu, I give a name to ...
2
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0answers
38 views

How to specify a polygon face toward to different lines

I have a parcel layer, a street of city layer, I want to find the parcels at the corner of two different street (mean a house with two face toward to 2 streets) I appreciate your suggestion for ...
2
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0answers
79 views

Convert a classification image to aggregated polygon in shapefile using gdal/python

My goal is convert a 2D numpy array to shapefile. The matrix results from a classification, so the numbers have a meaning. I solved my problem, but the solution is somehow involuted and complicated. ...
2
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0answers
116 views

Why is GDALPolygonize so much slower than ArcGIS Raster to Polygon?

I am attempting to polygonize a raster using GDALPolygonize() in a Python script. The script began polygonizing yesterday at 5pm and is still polygonizing now at 9:30 am. I have no clue how far ...
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0answers
33 views

Polygonize Missing Polygons

Polygonize is not capturing all of the pixels in an image that has been converted to 0s & 1s. The pics below show -original geotif -geotif recalculated to 0s & 1s -polygonize output As the ...
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0answers
473 views

Line to Polygon via Polygonizer in QGIS

My question is in the same vein as this one. I'm attempting to convert precipitation lines (Precipitación Media Anual) to a polygon for Mexico in QGIS using the Polygonizer plugin. After running the ...
0
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0answers
35 views

Polygonize only pixel values of 1 from a raster

I have a raster mask that I have created in QGIS (2.2.0) that consist of 0, 1 and nodata values. I would like to end up with a polygon dataset that consist of only the value of one pixels from this ...
0
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0answers
50 views

Polygonize a raster using GDAL JAVA bindings - passing raster pixel value to the resulting feature

I have a raster GeoTIFF file with values from 0 to let's say 5. When I run gdal.polygonize (I'm working with JAVA and GDAL bindings to JAVA) on it, I get features with corresponding polygons. The ...
0
votes
0answers
43 views

How to get the boundaries of a polygon by property

I have the cartography of my city (Santiago) and i need to obtain the nodes that conform the hull (not necessarily convex) of different districts, the boundaries. Each node has the same "DIS"( ...
0
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0answers
136 views

QGIS GDAL polygonize - how to set scale

I've got some old contour plots, paper copy only, that I'd like to be able to put into QGIS. I get as far as a successful polygonize into shp and it looks fine, but the scale is wrong. How might I ...
0
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0answers
214 views

Does Polygonize in QGIS 1.8.0 work correctly?

Does anyone else have issues with the Polygonize function in QGIS 1.8.0. When i use it is to extract details from larger raster images, through raster calculator, then polygonizing the resultant ...