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21,875 questions with no upvoted or accepted answers
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20
votes
0answers
575 views

SNAP vs. GDAL vs. Orfeo - image rescale, histogram cut

I work with a Sentinel-2 .jp2 image (red band, 10950 x 10950 pixels). My aim is to reach the same result what SNAP does with a Python script. See the SNAP method and parameters: So this is my ...
18
votes
0answers
1k 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 ...
11
votes
0answers
489 views

Alter Minimum Bounding Box Algorithm

I'm trying to create an algorithm similar to minimum bounding box (though it may end up looking nothing like it). In this case the angle will be passed as a parameter and given the angle I need the ...
11
votes
0answers
596 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, ...
10
votes
1answer
2k views

Plotting bar charts on maps in R?

I'm using plotrix in R to plot a state level map of the US. It has an excellent function floating.pie to put pie charts on each state. I'm wondering if there are similar functions within the plotrix ...
10
votes
1answer
881 views

Merge adjacent polygons and return all (adjacent and not adjacent) as Multipolygon?

I have a postgres database with administrative boundaries and their geometry. Each of those boundaries have an ident number. What I want to achieve: First I want to select all rows which are ...
10
votes
0answers
693 views

Simplify the straight sections of (multi)Linestring in PostgreSQL/PostGIS leaving the curved sections untouched

I have (multi)linestrings containing upwards of 5000 points and I want to perform two simplifications possibly using Ramer Douglas Peucker or alternative methods in PostGIS. The (multi)linestrings ...
9
votes
0answers
270 views

Cannot Open VRT of Sentinel2 image created by AutoCreateWarpedVRT

I am trying to create a warped VirtualRaster of a Sentinel2 image. Here the Python code I tried: from osgeo import gdal, osr srs = osr.SpatialReference() srs.SetFromUserInput('EPSG:32632') gdal....
9
votes
0answers
408 views

Accessing existing instance of QGIS from stand-alone python script

For my own data analysis pipeline, I am running a split screen setup with iPython notebooks on one side, generating variables from source data, pushing them to a CSV file which QGIS then reads/joins ...
8
votes
0answers
161 views

When using QGIS join by location, how does QGIS determine the first located feature option?

I have used QGIS process 'join attributes by location' in one of the models I have built and I have now been asked to explain in detail exactly how the model is determining the results. I am using it ...
8
votes
1answer
112 views

Coarse Woody Debris extraction

I created very high dense point cloud of some forest plots using terrestrial laser scanner. Then removed points above 1.3 meter to see the coarse woody debris (Fallen dead trees). Attached is the ...
8
votes
0answers
248 views

Missing roads from OpenStreetMap data with osmosis

I am currently trying to extract road networks from OpenStreetMap dumps downloaded on Geofabrik. I am using the following osmosis (version 0.45) command to extract roads: osmosis \ --rbf input.osm....
8
votes
0answers
330 views

Executing bidirectional dijkstra on TIFF image?

Can anyone indicate an example of how to do this? Link, tutorial etc... I started a discussion here about how to load a TIFF image like a graph nicely answered by @sehe. But, in this post the image is ...
8
votes
2answers
3k views

Login to USGS Earth Explorer and download Landsat imagery with Python

I want to login to the USGS Earth Explorer website at http://earthexplorer.usgs.gov/ with Python and download imagery from the Landsat Archive collection just by giving it username,password,path/row (...
8
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 ...
7
votes
0answers
382 views

Developing QGIS Python plugins using Jupyter?

Is it possible to run PYQGIS commands using Jupyter notebook and, if so, is there any documentation to develop QGIS plugins using Jupyter?
7
votes
0answers
195 views

How do I select the longest connected lines from PostGIS ST_ApproximateMedialAxis?

I used PostGIS ST_ApproximateMedialAxis to transform polygons representing mountain ranges into a series of lines. Now, I'd like to select only the "longest" line segment for each group, so that I ...
7
votes
0answers
224 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 ...
7
votes
0answers
102 views

Does PostGIS ConcaveHull exclude points/polygons in some cases, and buffer outward in others?

In trying to generate concave bounding polygons using PostGIS ConcaveHull, I am seeing what I think is strange behavior. When running with a 0.99 tolerance, the resulting polygon shrinks tight as ...
7
votes
0answers
199 views

Computing the horizon profile given a DEM in python

Can anybody orient me towards an open source python script that computes the 360° horizon profile (azi + elevation of highest topography in eye sight) from a single point (x,y,z) on Earth (account for ...
7
votes
2answers
657 views

Using QField with Multi-User Access also Offline?

I got 10-20 QGIS-Users which edit all one Project online and offline. Sometimes they do it at the same time. Until now we only used QGisDesktop with a PostGis Database stored in QGIS Cloud(50MB ...
7
votes
0answers
776 views

Landsat level-2 data comparison

I'm doing a temporal analysis of NDVI and temperature over 17 years, necessitating data from Landsat 5,7, & 8. I'm interested in using level-2 Landsat data available from https://espa.cr.usgs.gov/...
7
votes
0answers
2k views

Creating vector tiles from OpenStreetMap?

I need to understand the process of creating Mapbox Vector Tiles from OSM data in some detail -- in particular I need to fiddle with cutting out a lot of data (esp. buildings) to keep the final vector ...
7
votes
0answers
193 views

QgsSpatialIndex partial or complete overlap

I'm working on adding some functonality to a QGIS plugin. It currently uses a QgsSpatialIndex to efficiently compute whether the features of a vector layer intersect (potentially millions) of ...
7
votes
0answers
742 views

Efficiently calculate distance between raster patch edges

I have a binary raster which I've classified into patches using raster::clump. I now want to efficiently calculate the edge-to-edge, i.e. minimum, pairwise distance between patches. I am currently ...
7
votes
0answers
1k 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 '...
7
votes
0answers
553 views

Steiner tree problem: Optimal routes for Fibre planning on road network

I am trying to solve a large optimization problem where I have a set of nodes on a road network that need to be connected using fibre using the shortest possible amount of fibre. The problem is a ...
7
votes
1answer
317 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,...
7
votes
0answers
5k 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 ...
6
votes
0answers
142 views

QGIS can't load geometryless WFS tables published with QGIS Server

I created a QGIS 3.6 project on Windows Server 2016 x64 with two PostGIS layers: Layer A: Points Layer B: Datatable (No geometries) and configured QGIS Server options on the project like this: Now ...
6
votes
0answers
65 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 ...
6
votes
0answers
134 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 ...
6
votes
0answers
441 views

Why does QGIS 3.4 and higher create .tmp file instead of refresh editing layer after saving?

I downloaded QGIS 3.4.0 and try to save edits in .geojson file. I can save new objects, but not edits in attributes. Insted of it, QGIS creates .tmp file with my chаnges into the same folder with ...
6
votes
1answer
630 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, ...
6
votes
0answers
171 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 ...
6
votes
0answers
251 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 ...
6
votes
1answer
177 views

Spatialite KNN view in QGIS

My task is to calculate the average ground survey level for each tree in my dataset, using the 3 closest survey points (optionally within a 3m radius of the tree). I want to write this in a Spatial ...
6
votes
0answers
322 views

PostGIS issue with ST_Clip?

I'm trying to clip a raster using a polygon but I end up with a result that doesn't seem right and where some raster pixels are outside the polygon used for the clip. See image below where polygon is ...
6
votes
1answer
1k views

Creating polygon elevation contours?

I'd like to create polygon shapefiles to communicate elevation information on regional maps. I find these draped over a hill shade layer provide one of the best base maps. I can tell some ...
6
votes
0answers
208 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. ...
6
votes
0answers
150 views

When moving a feature in QGIS, is there a way to nudge it rather than use the mouse?

I need to move a lot of features (polygons) in QGIS to fit a newly Georeferenced scanned map that is slightly asymmetrically distorted. This is fine as it is just to provide a print copy. I end up ...
6
votes
0answers
207 views

Packing squares polygons in a raster grid

In the green area of the raster I have to fit as many square polygons as possible, of three different sizes: 3x3 cell size 2x2 cell size 1x1 cell size With the fact that the approach should be ...
6
votes
0answers
276 views

How to remove overlapping features by percentage?

I have geometry records of type MultiLineStringZM and I am trying to INSERT new records that overlap some of the records currently in the table. If they were type MultiPolygon I could use ST_Area() as ...
6
votes
0answers
280 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 ...
6
votes
1answer
433 views

Display pictures stored as bytea in postgresql column in qgis

does someone knows a possibility to visualize in a bytea column saved photos of a postgresql database in qgis? I would like to store pictures directly into the database, not just the link/ url.
6
votes
0answers
417 views

What are the considerations for choosing between WKT and WKB geometries?

There are many questions & answers here addressing how to convert between WKT and WKB geometries, and about the specifications or implementation details. But what are the considerations for ...
6
votes
0answers
406 views

PostGIS (Postgres 9.6) - order bounding box query results by date (large table)

I'm querying database entries using a bounding box with ST_MakeEnvelope and intersecting that with a coordinates column (type GEOMETRY), consisting of simple POINT(lng, lat) entries. I've created a ...
6
votes
1answer
473 views

Cellular Automata Markov for forecast LULC in R software

I would like to forecast land use changes by implementing the Cellular Automata (CA) Markov Chain models in R software. I have the classified LULC maps from 3 times periods (1992,2003,2014), and also ...
6
votes
2answers
214 views

Plotting a hyperbola, or, solving spherical triangles

I am trying to create a GeoJSON path containing lines of hyperbola, in order to recreate Decca Navigator charts in QGIS, something like this: The chart has nine lines of hyperbola plotted between ...
6
votes
0answers
86 views

Show Symbol (e.g. City-Marker) only when an associated label can be displayed

I'm building a map for a certain region with many cities to be displayed. Some of the smaller cities should only be displayed if they don't overlay bigger cities. While the labels of the smaller ...

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