Questions tagged [polygonize]

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

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QGIS Polygonize not working on large dataset

I have a 1.3 gigabyte shapefile I am trying to run through the vector polygonizer in QGIS. The lines intersect each other yet when I run it through it gives me "No polygons were created." Is ...
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Polygonizing global raster using Python/GDAL?

I'm looking to polygonize a global raster with 29 different categories. However, when I try to run it in QGIS, it either crashes or takes forever to load. I'm now trying to run it in python. import ...
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Classifying areas after feature to polygon

I am trying to classify areas based on the polygons created from using two separate lines as input in ArcGIS Pro's Feature to Polygon tool. The input looks like this first column in the image from the ...
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Polygons from lines with manually completed lines using vertex tool and snapping

I have a vector layer of lines (contours) which was a model output. Some contours are incomplete due to land barriers (necessary for the model) which produces something like this I have used the ...
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QGIS 3.20.2 Polygonize Gdal Missing

I'm trying to polygonize a (tif-)raster file in QGIS 3.20.2 but get the following error message: Algorithm 'Polygonize (raster to vector)' starting… Input parameters: { 'BAND' : 1, '...
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Converting complex depth contours to polygons in sf and R

I have a large dataset of depth contours downloaded from an open database. At the time of writing, these contours appear to contain the best available continuous depth model for my region of interest. ...
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Convert area between LineStrings to Polygon in shapely

I need to create a Polygon from the area enclosed by four LineStrings with real world data in shapely. In this example, I want to polygonize the area between b1, b2, t1 and t2. import shapely.wkt b1 = ...
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Joining a very large raster and shapefile in QGIS

I am using a very detailed 30 m x 30 m raster on deforestation (found here: https://storage.googleapis.com/earthenginepartners-hansen/GFC-2020-v1.8/download.html), I want to do all my analysis at this ...
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How to polygonize multi-band rasters to vectors with multiple attributes?

I'm using Python, and I usually polygonize rasters using rasterio like in this thread : How to polygonize raster to shapely polygons However, now face a new problem, I have two rasters with same ...
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processing.run('qgis:linestopolygons', ...) does not work properly

I am writing a QGIS plugin and for part of the process, I want to transform a Line layer (connected lines) into a Polygon layer. For this, I am using processing.run('qgis:linestopolygons') command. ...
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2 votes
1 answer
458 views

How to extract the boundaries of Shapely MultiPoint? [closed]

I have a shapely MultiPoint object but need to extract the boundaries into a Polygon object. I'm currently using the convex_hull of the MultiPoint object but my MultiPoint sets can have sharp inward ...
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Extracting polygons from scanned GeoRef images based on colours in QGIS

I would like to extract a polygon based on it's colour from a scanned map georeferenced in QGIS. In the image, I would like to extract all of the blue as a separate shapefile/GeoPackage instead of ...
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372 views

How to apply GDAL polygonize?

I am desperately trying to vectorize raster files in a loop for which I came across GDAL's polygonize function (https://gdal.org/programs/gdal_polygonize.html). However, I don't get the hang of it. To ...
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How to polygonize NDVI raster using GDAL?

I have raster with NDVI values. I would like to polygonize the raster to get vector where each polygon is a pixel. I have tried gdal.Polygonize as described in the documentation and that runs without ...
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PostGIS: Split polygons into intersecting and non-intersecting and grouping on overlap

I have a big query that I am looking to optimize. I am matching millions (expanding daily) of rows with Points against a mostly read-only table of (tens of thousands of) areas with (Multi)Polygons. ...
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2 votes
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Saving polygonized raster file to shapefile failed

I have a raster that I have polygonized (raster to vector) with QGIS 3.20.3. The result is a temp layer that can be displayed in the canvas. When I try to save the features to shapefile it runs until ...
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How to get float values instead of integers when polygonizing rasters using QGIS?

I'm using QGIS 3.16.13-Hannover to convert a TIF file (solar radiation grid cells) into a vector like a Geojson or Shapefile. I was confused that everytime I ran the polygonize workflow in QGIS, I was ...
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Calculate area for each raster value within a polygons (python) [duplicate]

I have a raster file and polygon shapefile. I need to calculate area for each raster value within a polygons. Example: the polygon below Total area = 1000 ha. I need an area for each raster value in ...
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How to add a border around a GeoTIFF?

I have a 200x200 GeoTIFF from which I am trying to create multiple polygons. I am using different range values to generate different polygons. However, the inverse of the polygons I want are being ...
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3 votes
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gdal_polygonize / QGIS Polygonize creates

The original data is a pdf converted to tiff then georeferenced. Then i did the sum of the 3 colors band to simplify the calculus When i launch the polygonise (raster to vector), this is very slow ...
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Polygonizing raster files using QGIS gives different area polygons between GDAL 3.3 & GDAL 3.0

I used QGIS with GDAL 3.3 to polygonize a raster file. Added a field using the "field calculator" to calculate the area of individual polygons. Finally, to calculate the sum of the total ...
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Polygonize RGB raster

I'd like to calculate the impervious area within a number of polygon subcatchments in QGIS. I have a geo-referenced RGB aerial image that identifies roads, driveways and roofs. Is it possible to ...
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3 votes
1 answer
132 views

Looking for QGIS equivalent of ArcGIS "Feature to Polygon" tool

I am looking for a tool (a workflow) in QGIS that does exactly the same as the "Feature To Polygon" in ArcGIS available with the Advanced license. I have seen a related question Seeking ...
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Extract altitude bands (polygon) from DEM (GeoTIFF)

I'm trying to extract altitude polygons from a DEM - 0 to 1000m, 1000 to 2000m, etc. I'm not sure what this is called (noob question, yes I know), and can't find help that points in the right ...
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QGIS Polygonize algorithm, converting raster to vector files different from Mac and Windows

We are trying to convert a single-band raster files with values 0s & 1s to Vector. When using the QGIS's internal algorithm 'Polygonize', the result is slightly off from a Mac then the ones from ...
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2 votes
1 answer
60 views

Extracting all possible polygons from set of different types of geometrical elements

I have an input, a set of different types of 2D geometrical elements with all its attributes (arcs, circles, lines, polylines, rectangles, polygons..). These elements can be connected end to end, ...
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1 vote
1 answer
595 views

"Layers were not correctly generated" error when polygonizing raster in QGIS

I have the raster of a river product of an image classification with the SCP Plugin, and i need to divide the land and the water that resulted of said classification, so i am attempting to polygonize ...
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2 votes
1 answer
87 views

Split layer with lines or with Polygonize (and keeping all features intact) - QGIS 3.18

I want to divide a polygon layer into different smaller polygons. I started by converting the main polygon into a line, then I used the Add line feature to draw the lines. Then I used the Split with ...
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NLCD 2016 Data in QGIS

I am struggling to convert the NLCD 2016 data to a shapefile in a CRS of WGS 84. I have three problems (that I think are simple) that I would love some help with: (1) It seems other's have the option ...
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Polygonize Rounds-Off Values [duplicate]

I am currently using rainfall data in determining rainfall patterns. But when I use Polygonize, the values on the attribute table of the created vector file were rounded off to the nearest whole ...
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4 votes
1 answer
271 views

How to polygonize raster with range of values?

I have a raster with range 0 - 1. I want to polygonize them in QGIS according to their value to be later classified from "Very Low" to "Very High". raster_value ...
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QGIS converting multiline layer into polygon doesn't work properly

I would like to polygonyze my layer. It includes between 6-20 separate lines. I was following the hint here: Converting line to polygon using QGIS but at some point I've got an error: Feature (2) has ...
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Splitting Vectors with Raster Layer

Does anyone know of a method to split vector data based on a corresponding raster layer. For example, I have a classification with two classes and have an overlaid vector layer as seen in the image ...
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Making polygons from interpolated points in QGIS

I need to know the extension of the area of a lagoon according to depth classes. I started from a point shapefile containing depth values and used the interpolation plugin and I obtained a raster file....
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Very slow segmentation using Python

I used both Python and QGIS to perform polygonization of a raster but the waiting times with Python are very long, while with QGIS the operation is done in a few seconds. Could you tell me the reason ...
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Reclassifying and vectorizing specifc classes in Google Earth Engine

My raster file has 29 classes and I applied 'Reclassify by table' in QGIS 3.16 to assign 1 to classes 15 and 24 only and all other classes were classified as 0. I applied the following script to ...
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Too many edges error on GEE

I have this code that works perfectly for small rasters. var image = ee.Image("users/parivash89/Cuneo_Reclassify") .toInt(); Map.addLayer(image); Map.centerObject(image); var classes = ...
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1 answer
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Google Earth Engine_Conversion to vector

I have a classified geotiff raster that has two classes 0 and 1. I changed its type to int and imported it from my computer to GEE using upload a new asset and I changed its var name to image and I ...
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Ways to speed up Polygonizing of rasters/orthophotos (binary)?

From a orthophoto of the Wadden Sea, I want to create a polygon from a class of this TIFF/raster (binary) representing an oyster reef, calculate the area of the reef and form a polygon around the reef ...
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Distinguish between filled polygon and boundary

I am trying to convert the raster images to vector and get the inner filled polygon. But the filled polygon and its boundary are wrongly detected for some cases. Below is the code where I tried to ...
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106 views

What's the theory (principle) behind shapely.ops.polygonize?

I am learning Python package Shapely, but quite confused about the principle behind the polygonize function --- shapely.ops.polygonize. How does this function work to polygonize a set of lines (...
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3 votes
2 answers
161 views

Converting/expanding line into 2D polygon using QGIS

I am brand new to GIS and am attempting to use QGIS to take an existing line from a shapefile and create a 2D polygon based on it i.e. I want to take a line and fatten it out a bit so it has an area. ...
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7 votes
1 answer
154 views

Cannot select input layers for the "Polygonize" tool in QGIS

I am trying to convert a raster layer to a polygon layer using QGIS 3.16. 2. When I open the polygonize tool, the program does not allow me to select any existing raster layers from the 'Input layer' ...
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QGIS does not polygonize [closed]

I have a .tif which I want to have polygonized. I take the Raster/Conversion/Raster to Polygon. QGIS 3.12 starts the process but never ends (once I waited half an hour). I maybe don't see a mistake. ...
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1 vote
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Converting lines to polygon based on matching attribute

In QGIS, is there a Plugin or a geoalgorithm that allows you to convert lines to polygons but incorporates a particular attribute? I have roadside kerbs which have a field for road name, and if ...
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2 votes
1 answer
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Polygonize area surrounded by buffer in QGIS

I have an automated system in QGIS that separates loops from GPX traces and works out their centroid using 'Polygonize' >> 'Keep N biggest parts' >> 'Centroids'. However, quite often it ...
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5 votes
2 answers
402 views

Merging cluster of points into polygons

This is my project: I want to convert all points that touch each other into polygons, something like this (I know I missed some of them): I tried using dissolve and convex hull to do that, but they ...
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  • 119
3 votes
1 answer
74 views

Smoothing zone edges

I am currently recreating a hazard map that was processed by another program. Is there a tool/plugin available that can be used to smoothen out the rough edges of the grids? Attached is the current ...
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2 votes
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38 views

Polygonize RGB mage considering all 3 bands simultaneously

I'm using the rasterio.features.shapes method to generate GeoJSON information from a PNG file. This answer shows what I'm trying to do, except I need to analyze the RGB bands simultaneously otherwise ...
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5 votes
1 answer
215 views

Transforming line into polygon with Geometry Generator

I would like to turn my line into polygon in the symbology. I found some hint here: https://anitagraser.com/2017/04/08/a-guide-to-geometry-generator-symbol-layers/ but I am not sure of the expression, ...
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