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

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35 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 ...
8
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1answer
101 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 ...
1
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1answer
48 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
108 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 ...
1
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1answer
34 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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30 views

Gdal Polygonize Java

I tried to use the gdalPolygonize function within in java. What I did Installed gdal-111-1800-x64-core from the following link ...
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0answers
17 views

polygonize some raster pixels based on their value in PostGIS

I need to extract and polygonize only those pixels of a raster that have a value (e.g.) greather than 2000.0 The reason is that I wish to do an operation like the following one (which is done only on ...
0
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1answer
63 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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43 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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301 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], [ ...
0
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1answer
97 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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21 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 ...
0
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1answer
35 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 ...
0
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0answers
31 views

increase gdal_polygonize's capacity

I have a very big PNG (82500x40900) with more than 5000 polygons. I want to use gdal_polygonize but the geojson output shows that gdal_polygonizer stopped after 4770 polygons and the geojson isn't ...
0
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1answer
51 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" ...
0
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1answer
102 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?
2
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0answers
92 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 ...
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0answers
85 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 ...
2
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1answer
88 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
68 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
98 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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72 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 ...
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76 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 ...
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1answer
73 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?
1
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1answer
74 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 ...
1
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1answer
958 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
211 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 ...
2
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0answers
53 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 ...
0
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1answer
56 views

Defining areas for inclusion in polygon conversion using ArcGIS for Desktop?

Using ArcGIS 10.2 for Desktop, I am trying to create a polygon shape(s) from a raster image. Is there a way to indicate areas I do not want included in the shape. Similar to a buffer I suppose, but ...
1
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1answer
62 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 ...
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48 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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116 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 ...
2
votes
1answer
115 views

How to split Polygons by line grid?

I want to split a polygon by a intersecting line into different parts, exactly like in this post(Qgis - Is there a way to split a polygon layer with a line layer?). I have a vector grid to cut the ...
0
votes
1answer
122 views

How to convert boundaries in image to polygons in QGIS

I have an image from a cities districts and their boundaries and I need them as polygons in QGIS. I tried "Raster -> Conversion -> Polygonize (Raster to vector)" as described here, but that ...
0
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1answer
200 views

How to colour contour lines in .shp file when the lines are not meeting in QGIS?

I am doing bathymetry analysis, where I would like to color the contours one by one in the case land is rising (or sea level going down). There is a comprehensive explanation about coloring contours ...
0
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1answer
112 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 ...
7
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2answers
714 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 ...
0
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2answers
153 views

I have a table with a series of lat/long points - how do I convert them into polygons?

I have an Excel sheet with about 150 points (lat and long in decimal degrees) which belong to about 15 different polygons. The columns I have are FID, NAME (the same between polygons), POINTS (points ...
2
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0answers
47 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
151 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. ...
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2answers
274 views

Unsuccessfully trying to iteratively run gdal_polygonize in a batch file [closed]

Thanks in advance for your help with this. I've been reading, experimenting, and banging my head against the wall for a couple days on this, and could really use some assistance. This is my first ...
0
votes
1answer
75 views

Associate points with polygon QGIS 2.2

I want to associate a point layer with a polygon layer so that I can do zonal statistics. In the image below, the polygon layer represents roughly the metro area of a certain city. The point ...
0
votes
1answer
158 views

gdal's polygonize function (via qgis) is not turning monochrome rasters into readable shapefiles regardless of inversion of color scale

I've tried polygonizing this monochrome bitmap as this: and this: and either way it ends up looking like this when (zoomed in) after gdal's polygonize operation: Is there any way I can tell ...
0
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1answer
261 views

Polygonize(raster to vector) [closed]

I have been install QGIS 2.0.1.when I use Polygonize (Raster to vector)for convert jpg to shp I get error message such as: C:\windows\123.exe is not recognized as an internal or external ...
0
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2answers
148 views

Low resolution raster conversions to vector yielding millions of single pixel polygons. Trying to merge all directly adjacent polygons

I'm trying to scan plain pdf maps containing color-coded geographic regions and convert them into undifferentiated (I don't actually need them to contain any attribute data) overlays. My workflow is ...
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1answer
119 views

Is there any way to add an area column to new shapefile created from raster with gdal's polygonize in the same step?

I've been going through a fairly lengthy process of polygonizing very intricate raster images, then creating a new layer with the extra area attribute, so that I can then remove the millions of tiny ...
2
votes
2answers
413 views

How do I create a polygon layer from multiple touching line segments in QGIS?

I'm trying to create a base map for a Maine Coastal area, and wanted to create a polygon layer of the land cover from the coastline in QGIS. Whether I created the coastline vector layer from the USGS ...
5
votes
1answer
806 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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1answer
430 views

GDAL polygonize only certain raster values

I want to polygonize a raster file with GDAL. I only want to rasterize cells with a value of 0. Is it possible to specify that within the polygonize function or do I have to modify my raster before ...
3
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0answers
210 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 ...