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28,969 questions with no upvoted or accepted answers
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26
votes
0answers
2k views

Leaflet v1 plugin: layer control for ungrouped, grouped, and nested-grouped layers

I need a Leaflet plugin which extends L.Control.Layers. I have the following requirements: works with Leaflet 1.x handles ungrouped layers alongside grouped ones handles nested layer groups does not ...
16
votes
0answers
1k views

Digitizing in stream mode in QGIS using a tablet

How can I digitize in stream mode in QGIS, using a wacom cintiq tablet? Freehand it's no use. I need something like MNDR stream digitizing extension for ArcView 3.x, which allows continuous tracing, ...
14
votes
0answers
205 views

Unit testing for QGIS 3 plugins

There is a nice resource on unit testing for QGIS. There is also a post on this, Writing automated tests for QGIS plugins, which requires the use of docker and relies on QGIS 2 plugin - QGIS Tester. ...
14
votes
0answers
723 views

Parsing file format for attributes in Raster Product Format (RPF) maps and imagery?

I'm trying to implement an open-source NITF reader (using only java, no external libraries such as GDAL or NITRO), and its mostly going OK. However I'm having trouble understanding the RPF extensions, ...
12
votes
1answer
472 views

Point cluster symbology for different categories without overlapping symbols

I'm trying to visualize crimes based on if the crime happened during day or night time. I've tried using the point displacement tool but I'm not satisfied with the results because the readability for ...
12
votes
0answers
1k views

Constructing a Voronoi diagram using a complicated travel time metric

I have in my possession four sets of shapefiles: 1. Locations (points), around 1000 2. Roads (lines), each road has a speed attribute 3. Terrain (polygons), each zone also has a speed attribute 4. ...
11
votes
0answers
361 views

High PostgreSQL/PostGIS memory and disk usage when saving QGIS project

Why would simply pressing the "save" button in QGIS cause my local PostgreSQL instance to cause memory and disk usage to spike to "Not Responding" levels? Seems to me like the ...
11
votes
0answers
405 views

Producing time-space cube in QGIS?

Although I have seen many examples about doing this at ArcGIS Desktop, I am still trying to find a how to using QGIS. What I want to do is something like the image below.
11
votes
0answers
2k views

Extract TopoJSON directly from PostGIS

I have a simple "region" table: id (TEXT), name (TEXT), geom (MULTIPOLYGON). Here's the query I can use to extract a GeoJSON FeatureCollection: SELECT row_to_json(fc) FROM ( SELECT '...
10
votes
1answer
5k views

C# implementation of concave hull / alpha shapes

I'm looking for a C# implementation of the Concave hull (alpha shapes) algorithm. I already found several Java, Python and C++ implementation but no C# version. The other implementation are quite ...
10
votes
2answers
7k views

Downloadable, Open Source, IP GeoLocation database

I have an open source project I need a similarly open source IP GeoLocation database for. i.e. IP address to country (and ideally city). Ideally with a license that allows redistribution. This is a ...
9
votes
0answers
134 views

Reading raster backward using GDAL

I am currently working on two-scan raster algorithms (euclidean distance transformations, cost surface analysis, etc.). Those algorithms require a line-wise forward raster scan (from top left to ...
9
votes
0answers
341 views

Remove reference to raster layer object PyQGIS

I am developing a plugin to load a set of raster files on QGIS. When there are a large number of files to be loaded, the main UI is freeze. So I use QgsTask to move the creation of raster layers to a ...
9
votes
2answers
913 views

Shapely with Rtree versus STRtree

I have a huge interrogation regarding the performance difference between Rtree and STRtree included in Shapely. Below is a short code where we create randomly 250 000 triangles (defined by 4 vertice) ...
9
votes
1answer
2k views

Editing Layout-Items after loading a QPT-Template in QGIS 3 with Python

I am facing a problem with the new Layout API while implementing a plugin for QGIS 3. Starting point is a layout template in qpt-Format, which contains different elements like (attribute) tables, map, ...
9
votes
0answers
262 views

ESRI Runtime Geodatabase Shape storage

Does anyone out there know the geometry storage encoding for ESRI's Runtime Geodatabase (.sqlite) format? aka mobile geodatabase. There are 'GDB_ tables', 'st_ tables', 'RTREE indexes' and other ...
9
votes
0answers
427 views

MapScript with Python 3

I am trying to build raster summarizing features into a GeoDjango webmap, and would like to use the django-raster and django-wms packages to do so. I believe that I have them set up correctly, but am ...
9
votes
0answers
2k views

Exporting a 16-bit image from QGIS?

Could someone explain how to export from QGIS a 16bit image. I have imported data and coloured it as I want, but need to export it as a 16bit image, as 8bit is giving a terracing effect.I believe I ...
9
votes
0answers
971 views

ogr2ogr (or other) simplification of polygons with shared boundaries

I am trying to simplify a collection of 100,000 or so polygons containing nearly 4 million vertices. The data is stored in a 2GB shapefile so there is no explicit representation of the topology ...
9
votes
0answers
285 views

Defining partial or complete overlap with QgsSpatialIndex

I'm working on adding some functionality to a QGIS plugin. It currently uses a QgsSpatialIndex to efficiently compute whether the features of a vector layer intersect (potentially millions) of ...
9
votes
0answers
1k views

Evaluating map projection scale error

This is related to a previous question How to determine projection parameters when customizing a projection I posted. I am trying to quantitatively evaluate scale distortion associated with choosing ...
8
votes
0answers
273 views

Accessing watershed boundary for lakes in R

I have had success accessing unique database IDs and polygons for various lakes in the US. I'm now looking to get polygons for the watersheds associated with these lakes, but have stumbled a bit. ...
8
votes
0answers
1k views

Georeference an unreferenced image using rasterio in Python

I have unregistered/unreferenced 6 band TIFF images that I have been trying to export as georeferenced GeoTIFFs. The GPS coordinates of the corners of each image is known and each image is 1024 height ...
8
votes
0answers
255 views

Calculate volume of space defined by multiple overlapping 3D polygons

I have thousands of 3D polygons scattered in space but they mostly overlap with many of their neighbors in big extent. Is there any way how to compute volume they define effectively? I would love ...
8
votes
0answers
178 views

Processing post-execution script hook to clear scratch layers?

I've been cobbling together some Processing scripts for QGIS 2.18 (I'm not a fan of QGIS 3 scripts), and I keep running into one particular problem: my script creates a lot of scratch layers and they ...
8
votes
0answers
291 views

Multithreaded DB connection for QGIS plugin

I am using QGIS 2.18.21 and PostgreSQL 9.6. on a Windows 8 machine. I am trying to do processing of a certain database task in the background, and I want the user to be able to continue to work in ...
8
votes
0answers
2k views

Setting band names when writing multiple layer rasters using GDAL with Python?

I want to write a raster file (using GDAL+Python) with multiply bands. However, I do not know how to named bands. Their names are always "Band 1", "Band 2", etc. I search and found a function that ...
8
votes
1answer
2k views

Clipping raster brick object in R

I have MODIS NDVI TIFF files for a year I want to first clip it with a irregular polygon (not by its extent only) of my study area and save it as a multi band raster in TIFF format The TIFF image are ...
8
votes
1answer
384 views

Opening MOD17A3 in ENVI so it is properly georeferenced?

I am using ENVI 5.1 on Windows 8. I am trying to open a MOD17A3 (MODIS Net Primary Productivity standard product - L4) .hdf file which I downloaded from the USGS website. I am still a beginner at ENVI,...
8
votes
0answers
2k views

How to prevent cross-world lines in ggplot world map?

I'm having issues displaying 'great circles' paths and polygons in ggmap, an extension of ggplot2. Please enter the following code to replicate my issues: https://gist.github.com/Robinlovelace/...
8
votes
0answers
937 views

What is the convergence threshold for ArcGIS Iso Cluster?

The ArcGIS tool Iso Cluster Unsupervised Classification does not seem to have any documentation on the convergence threshold used in the tool. To compare, Erdas Imagine has all of the necessary ...
8
votes
1answer
3k views

Using MMQGIS hub lines tool in QGIS?

I am trying to connect source and destination points with the hub lines tool in MMQGIS. I have gone through the other posts on this subject but couldn't figure out what I am doing wrong. I have ...
8
votes
1answer
1k views

Rounding numbers in Raster Legend in QGIS?

Is it possible to have the numbers in the raster legend automatically rounded off? In the example below I'd like the labels to be 8, 29, 51 and so on. I know I can manually edit the labels, but is ...
7
votes
0answers
75 views

Georeference single drone image from EXIF data

Looking for an algorithm (python, formulas, whatever...) to georeference a single drone image based on its EXIF data. Specifically, I need to translate drone GPS latitude and longitude (after ...
7
votes
1answer
3k views

Creating raster from point values

I have a raster whose pixel values are 0 or 1 (b/w areas in the image below) and data type is Float32. I made a point layer from each individual pixel's center. Then I made some calculation for all ...
7
votes
0answers
627 views

Add private plugin repository to QGIS 3.4

I want to add a repository to my QGIS 3.4 which is on a private server. The repository contains all files needed (plugin.xml and metadata.txt for example) and has the structure as described here: Is ...
7
votes
1answer
3k views

Filtering a layer based on property that's an array in with Mapbox GL JS?

I've got a relational dataset broken into two layers: members and organizations. They're GeoJSON, with features that look something like this: // Org Features { "type": "Feature", "geometry": { ...
7
votes
0answers
444 views

Labelling a rubber band (QgsRubberBand)

It is possible to label QgsRubberBand or QgsVertexMarker with a text annotation (QgsTextAnnotationItem). See this MWE: ... r_polyline = QgsRubberBand(iface.mapCanvas(), False) r_polyline....
7
votes
0answers
899 views

Using WFST in Leaflet: can not move/delete features

I write a Leaflet app which makes use of two plugins Leaflet.Draw and Leaflet.WFST. The first allows to create/edit/delete features, the second saves changes to my PostGIS database hosted by GeoServer....
7
votes
0answers
364 views

QgsRubberBand Move Event

So, basically I've created a QgsRubberBand which copies feature from layer. And I need to be able visually move this rubberband on mouse event 'move'. Actually same visualisation like during self....
7
votes
0answers
362 views

GDAL contour line generation at DEM edges

In a Python application I use gdal.ContourGenerate() to generate contour lines (GDAL version 1.11.4 and 2.2.1) from DTED tiles. DTED tiles overlap at the top and the right with neighboring tiles. ...
7
votes
0answers
1k views

Importing numpy array into QGIS?

I have some computation on a numpy array and want to display the result in QGIS. So far ok, but loading the result into QGIS fails. Here my code fragment: zData2 = np.subtract(myarray,zData2) #do ...
7
votes
1answer
3k views

Editing metadata in QGIS?

How do I edit metadata in QGIS? I found the plugin Metatools which is experimental and did not work for me. In Metatools I always get the information ...unsupported metadata standard! Only ...
6
votes
0answers
81 views

Saving ArcMap/ArcGIS Pro symbology to a PostGIS DB for each layer

I want to have a default style/symbology assigned to each layer in a PostGIS database so that whenever it is loaded in ArcMap/ArcGIS Pro, it will come up with the default style. There is a way in QGIS ...
6
votes
1answer
75 views

Difference between QGIS export and gdalwarp

Does QGIS export/save as use a different projection system/process than gdalwarp? I am working with MASIE ice coverage data available here. My goal is to automate the process of reprojecting the daily ...
6
votes
0answers
137 views

When NOT to create spatial index

As I realized once again connected with this answer to Joining attributes by location using QGIS, creating a spatial index can result in huge performance improvements. However, I was wondering why ...
6
votes
1answer
140 views

QGIS 3.6 and QGIS 3.10 report different geometry types for the same shapefile

I used QGIS 3.6.3 to create a polyline shapefile, and the program reported the polyline as LineStringZM. When I opened the same shape file in QGIS 3.10.3-2, the polyline was reported as ...
6
votes
0answers
138 views

OGR failing to unpack polygons and respective holes from shapefile

I'm trying to unpack shapefiles in Python (v3.7.4) using the GDAL-OGR library (v2.3.3). Each shapefile has only one feature containing multiple polygons with holes. They cannot be produced differently....
6
votes
0answers
118 views

How to do a Lee’s Tetrahedral Conformal Projection of Antarctic/South pole on QGIS?

I want to do map of Antarctic using the Lee's Tetrahedral conformal map projection as the image below using QGIS version 3.4. Is it possible to make a custom CRS to do it? If yes, what's the ...
6
votes
1answer
80 views

Difference between merge and create virtual raster

I have the DEM of a defined region that has been split into sub-DEM with a resolution of 1 km x 1 km. When I merge the sub-DEM to create a single DEM (Raster -> Miscellaneous -> Merge), the overall ...

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