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

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7
votes
4answers
511 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 ...
7
votes
2answers
418 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 ...
5
votes
1answer
757 views

Qgis polygonize problem - DLL load fail

I have a raster file and I want to perform the method "polygonize". Then the problem occurs, that is shown on the screenshot. It doesn t have anything to do with the rasterfile format, I veryfied. ...
5
votes
3answers
635 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 ...
4
votes
1answer
202 views

How can I fix DLL loadfailed with Polygonize in QGIS 1.8? [duplicate]

Possible Duplicate: Qgis polygonize problem - DLL load fail I'm getting the following error message when I try to use the polygonize tool in QGIS 1.8 (windows 7): Traceback (most recent ...
4
votes
1answer
577 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
votes
4answers
432 views

How can I create polygons of the area surrounded by roads / lines?

I'm currently trying to create polygons that represent the areas surrounded by roads. The roads are stored in PostGIS as points / lines so I have flexibility over what I can do with them. I'm ...
3
votes
0answers
119 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
votes
1answer
53 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.
2
votes
1answer
112 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
votes
1answer
54 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 ...
2
votes
1answer
3k 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 ...
2
votes
2answers
276 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 ...
2
votes
1answer
117 views

From Raster to Masked and Filtered Polygon Vector

I have a set of rasters (geologic risk) from which I want to extract zones with a specific color, clipping them with a polygon (administrative borders), outputting a shapefile. I'm using QGis (and ...
2
votes
1answer
450 views

polygonize and raster tools [closed]

ok simplest question i have asked i think. but im a running QGIS 1.7.4 and there are no other tools in the dropdown menu other than raster calculator. I have seen in a lot of online demos tools below ...
2
votes
0answers
40 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 ...
2
votes
0answers
33 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 ...
2
votes
0answers
47 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
votes
0answers
43 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
votes
0answers
124 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
votes
0answers
158 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 ...
2
votes
0answers
175 views

Polygonize problem [duplicate]

Possible Duplicate: Polygonize function doesn’t overlay the shape file over the raster file When using "Polygonize" in Quantum GIS, I'm getting a polygon shapefile output that is a mirror ...
1
vote
1answer
59 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
vote
1answer
339 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 ...
1
vote
1answer
81 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 ...
1
vote
1answer
289 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 ...
1
vote
1answer
264 views

Qgis - raster values become integer when Polygonizing

When using the GDAL plugin, "Polygonize (raster to vector)" any values in the resulting vector layer is truncated to integer. I have a raster showing windspeeds in squares of 500*500 meters, in the ...
1
vote
1answer
66 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 ...
1
vote
2answers
177 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 ...
1
vote
1answer
311 views

Polygonize function doesn't overlay the shape file over the raster file

To convert the raster into a shapefile I use raster->conversion->polygonize but QGIS doesn't open the new layer overlayed the first (the raster) but reflected above it. I read this question ...
1
vote
1answer
758 views

DLL load error with Gdal polygonize in QGIS 1.8 (windows 7) [duplicate]

Possible Duplicate: Qgis polygonize problem - DLL load fail [I had already posted this question, but was closed and redirected to a supposedly duplicate question. I'm re-posting since I ...
1
vote
0answers
17 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 ...
1
vote
0answers
50 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 ...
1
vote
0answers
33 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 ...
1
vote
0answers
58 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 ...
1
vote
1answer
47 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
vote
1answer
49 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 ...
1
vote
0answers
40 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 ...
1
vote
0answers
541 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 ...
1
vote
0answers
18 views

Raster to Vector seems not to work [duplicate]

Possible Duplicate: Qgis polygonize problem - DLL load fail When I'm trying to invoke the Polygonize Module in the Raster Tab I get the following error message (I did give bothe the source ...
0
votes
1answer
26 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
votes
1answer
36 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
votes
2answers
113 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 ...
0
votes
1answer
62 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
131 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
votes
1answer
201 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
votes
2answers
123 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 ...
0
votes
1answer
33 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?
0
votes
1answer
36 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 ...
0
votes
1answer
117 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 ...