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

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37 views

gdal_polygonize returns with a strange error

i'm trying to execute gdal_polygoinize.py command. I have a main python method that takes in input a raster file and a output shapefile, and then calls a method named polygonize.py that builds and try ...
5
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4answers
182 views

How to speed up raster to polygon conversion in R?

I've decided to process my Landsat data in R instead or ArcGIS - due to my missing knowledge of python and and because of (assumed) high computation capacities of R. I want to : import r1 raster to ...
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2answers
144 views

How to polygonize raster to shapely polygons

I am seeking an open-source python solution to convert raster to polygon (no ArcPy). I did know the GDAL function to convert raster to polygon, and here is the manual: http://pcjericks.github.io/py-...
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3answers
78 views

DEM polygonize (raster to vector) doesn't work for contour lines less than 1 meter apart? (QGIS)

I tried to make polygon from DEM (geotiff) in QGIS. My requirement is that elevation value was every 0.5m of polygon. If I use the function polygonize (raster to vector) , polygon is created but ...
3
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1answer
61 views

OSM roads polygonized in PostGIS = nonsense

I have a dump of OSM data in my city and wrote a query to polygonize it. In the first attempt, the result looked like this: The problem was that OSM lines were not split and I guessed that the ...
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1answer
63 views

Polygons between contour lines in QGIS?

I am trying to create polygons between contour polylines within a defined area (for which i have both polygon and polyline shps) but I seem to be thwarted at every turn. Using QGIS 2.14, I am sure it ...
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1answer
24 views

How to polygonize using GeoDjango and PostGIS?

The code of GeoDjango-1.9.2 contains reference to the function ST_Polygonize at: https://github.com/django/django/blob/master/django/contrib/gis/db/backends/postgis/operations.py#L132 But is it seems ...
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191 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 ...
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138 views

C/C++/C# Library for raster to vector conversion

I am looking for an "open source" C/C++/C# Library able to convert raster to vector data (Polygonize). I know gdal_polygonize.py is doing the job, but I can't use Python. Portrace is an other option, ...
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1answer
78 views

QGIS 2.12 Lines to Polygons not work properly

In QGIS 2.12.3 I have a small shapefile with lines (as often occurs in parcel boundary datasets) of 2 vertices each, snapped to each other (no topology errors, no dangles, no intersections). But the "...
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29 views

polygonize raster so that every cell becomes a polygon?

Is there a proper way of polygonizing a continuous raster so that every cell becomes a polygon? What I do now is make the cells differ enough so that the algorithm makes different polygons of them. ...
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1answer
5k views

How to convert lines to polygons using NetTopologySuite?

I am trying to convert lines to polygons using NetTopologySuite(a C# port of Java Topology Suite JTS). I ran the sample console code succesfully and it generated two polylines. I then tried to run ...
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1answer
42 views

Create kml from binary raster

I have a binary raster (values - 0 & 1) - I want to create a shapefile (KML for use in Google Earth) of the white area only (value = 1). Is there a simple method to do this?
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146 views

python script in QGis - help using gdal.Polygonize

I want to create a very simple script in python that polygonizes a raster. Based on python cookbook + forums search I wrote the following code #import des modules from osgeo import gdal, ogr from ...
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1answer
33 views

How can I make a polygon from intersecting lines of different layers in QGIS?

I am constructing a geological map which involves constructing boundaries to areas which vary in style across their length depending on how well defined they. To do this I have created two distinct ...
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1answer
125 views

Creating polygons representing specific range of values within raster using QGIS?

Using QGIS, I started with LIDAR points (every 5 m) on a 90’000 ha area and then converted it in a raster of elevation (interpolating to fill some holes in LIDAR data). Now, I want to get a polygon ...
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1answer
446 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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1answer
66 views

Creating Polygon from a Raster

I have a Raster representing climate data. I converted the raster to vector using the tool raster to vector (Arc Map) and i got something like below: Can somebody help me out by guiding me in actual ...
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3answers
129 views

OSGeo4W GDAL Polygonize Batch Convert?

I'm trying to use GDAL polygonize to run a batch convert but I cannot for the life of my figure out a way to get it to read a text file as input that contains all of the commands. Do any of you know ...
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0answers
116 views

how to orthogonalize building outlines

I'm looking for a way to orthogonalize building outlines which I've extracted from a high-res DEM. I'm using the FOSS GIS stack (QGIS, GRASS, SAGA, PostgrSQL, PostGIS) and can code in Python (or Java)....
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1answer
195 views

Building a polygon over a reachable area

I am currently working in the field of isochrones and the underlying algorithms. What now causes problems is not the calculation if the isochrone itself, but the visualization of the results. The ...
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1answer
150 views

Trouble using gdal utilities in python (no output files created)

I am trying to use gdal utilities like gdal_polygonize in python to polygonize my raster image but I'm having trouble understanding the commands. What I mean is in some places the command is of the ...
4
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1answer
217 views

Raster to vector (polygons) with generalisation

I have created rasters showing different types of vegetation (bushes, trees, open land) with help from lidar data. Now I'm looking for a method to turn these images into polygons. I'm using a Mac ...
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1answer
71 views

gdal_polygonize with World File

I have this image that I want to convert it to GeoJSON. And I have this World File: 0.0388048118 0.0 0.0 -0.0387897595 697054.11331 4458020.56656 When I try to run the gdal_polygonize command ...
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3answers
792 views

Convert polyline with Left ID and Right ID to polygons with ID

I have a polyline shape file which contain Left Id and Right ID information and struggling in converting this polyline layer to polygon with ID via arcpy. I am using ArcGIS(editor) license so feature ...
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1answer
101 views

polygonize giving duplicated polygons

I am trying to reproject some ascii files and convert them into shapefiles. I am new to python but looking at some code online and help files I was able to write the following code to run on Python ...
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87 views

QGIS Polygonize (GDAL) problem - Null value in attribute

Is it possible to use Polygonize in QGIS (GDAL) so that a line shapefile is converted to a polygon shapefile with an attribute(s) in the line file carried into the polygon file. I am trying to build ...
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922 views

Polygon of Voronoi cell using scipy.spatial?

I have points (e.g., lat, lon pairs of cell tower locations) and I need to get the polygon of the Voronoi cells they form. from scipy.spatial import Voronoi tower = [[ 24.686 , 46.7081], [ ...
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1answer
903 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: ...
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1answer
168 views

Usage of gdal.Polygonize(,,,)

I am trying to code gdal_polygonize source.png -f "GeoJSON" destination.geojson with the java-bindings of gdal. I don't know how to make gdal.Polygonize(...) create the "DN"-Fields one obtains when ...
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26 views

gdal_polygonize floating values [duplicate]

gdal_polygonize converts whatever rasters values into vector integers as it is based on the GDALPolygonize() function (http://gdal.org/gdal__alg_8h.html#a3f522a9035d3512b5d414fb4752671b1). It is ...
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4answers
1k views

Generate polygons from a set of intersecting lines

This is a simple and quite common question which has already been asked for different purposes (see this link and this too, for example), here, however, we are looking for not a software package but ...
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1answer
49 views

Code of _gdal.pyd

I want a deeper understanding of how gdal_polygonize.py works. It uses gdal.Polygonize and gdal.Polygonize refers to _gdal.pyd. Where can I see the actual algorithm where the actual polygonization ...
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1answer
74 views

Is gdal_polygonizer creating a wrong geojson?

I have this PNG and I use gdal_polygonize 0VxOhek.png -f "geojson" 0VxOhek.geojson This is the output. There is a "features"-array which contains many objects with "type", "properties" and "geometry" ...
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1answer
211 views

gdal_polygonize ignores some polygons

I want to polygonize this PNG. I try gdal_polygonize pic.png -f "GeoJSON" polygonized.geojson but I get only 11 polygons instead of more than 20. What is the cause or how can I fix it?
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0answers
138 views

QGIS polygonize GDAL DLL load failed

I'm using QGIS 2.6.1 and i've been having problems using the polygonize function. I keep getting a "DLL load failed" import error. I've searched older threads which unfortunately weren't able to help....
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160 views

Error running polygonize from QGIS!

I'm trying to vectorize a raster image and when I'm running polygonize within QGIS 2.6.1. I'm getting the following message: Traceback (most recent call last): File "C:\PROGRA~1\QGISBR~1\bin\...
2
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1answer
156 views

Problem or ERROR in converting from raster to vector!

I wonder if anyone could help me out, i am kind of a beginner at QGIS. I´ve built a DEM for a project that i am developing than i´ve made the slope raster with the terrain analysis,it seemed that ...
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0answers
96 views

Geoserver does not render polygon properly

I am trying to a get polygon layer from CSV file. I chose to do it via rasterization and polygonization in QGIS, howerver, Geoserver has problems to correctly render some polygons. This is how the ...
2
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1answer
198 views

Which algorithm does gdal_polygonize use?

I would like to know which algorithm (i.e. Sobel operator ) is used to extract the polygons in gdal_polygonizer. I searched here and here but could not find it. Any help would be appreciated.
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105 views

Diminishing performance of gdal_polygonize in a python subprocess for GRASS to PostgreSQL

I have written a python script to polygonize GRASS rasters into a PostgreSQL database using the gdal utility gdal_polygonize: sub.call('gdal_polygonize.py -8 gdb/quercus/{0}/cellhd/{1} -f "PostgreSQL\...
1
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1answer
113 views

Does CartoDB automatically fill in Polygon data for city/state? How?

I'd like to upload a spreadsheet that has custom city/state information and have CartoDB automatically fill in the polygon data - is this possible? If so, how?
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89 views

Extract polygons of PNG with GdalOgrInJava

I have PNG pictures with polygons of different colours on them. What I plan to do is to extract these Polygons using the polygonize function (see here) Then I will try to encode the polygons in ...
5
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1answer
1k 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 ...
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2answers
1k 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 ...
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1answer
131 views

Converting rasters to polygons through cell centers

With arcgis, it is possible to convert a raster image to a polygon representing the boundary of the raster using the Raster To Polygon tool. The output polygon will follow the cell edges of the ...
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1answer
2k views

qgis polygonize error 4 “file does not exist in the file system”

When I try to convert a raster DEM (in asc or geotif format) to polygons I get the error below. ERROR 4: `Y:/GIS/oversvmmelser/tmp/out.tif' does not exist in the file system, and is not recognised ...
2
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1answer
381 views

QGIS show gdal_polygonized file in EPSG:54004 instead of EPSG:3857

I am polygonizing a TIFF with the gdal_polygonize.py and the resulting Shape is shown in QGIS in the wrong projection - EPSG:54004 instead of EPSG:3857. I have a TIFF in EPSG:3857 and polygonize it ...
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0answers
55 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 ...