3
votes
2answers
114 views

How to select all files in a directory for merging in Processing?

I'm writing a generic script which involves writing shapefiles to a directory which are then merged together. After writing the files out to the Output folder, I'm trying to get the ...
6
votes
1answer
72 views

Competing approaches to line & polygon simplification

There seems to be a few theoretical options around at the moment for geometric simplification. Douglas–Peucker seems the most established, followed by Visvalingam's approach (used by d3.js). Now ...
0
votes
0answers
40 views

Error: Algorithm not found

I wrote the following code to start using QGIS APIs. in a very short script seen below, the "Error: Algorithm not found" is thrown and "print processing.alglist()" is showing none. Any idea why this ...
2
votes
0answers
52 views

How to detect turns of a route?

I'm doing a Python simulation of a vehicle, driving along a specified path. I generate dummy GPS readings, that fetch the current position of the vehicle, with some randomized error added. After a ...
2
votes
0answers
38 views

How to add nodes into graph

I'm new to qgis and in here I want to find a path between two selected points on the map(Roads-vector layer). The points are selected by the user, using mouse clicks. So here I used the astar ...
0
votes
0answers
20 views

'QgsGraph' object does not support indexing

Traceback (most recent call last): File "/home/kasun/.qgis2/python/plugins/floogin/floogin.py", line 246, in findRoutes path=self.astar.astarSearch(graph, start, end) File ...
3
votes
2answers
227 views

What's wrong with my IDW interpolation function (Python)?

Original Question Can anyone see what's wrong with my custom IDW interpolation below? I know there are existing libraries that can do this for me, but for various reasons including educational and ...
3
votes
3answers
1k views

How to find if two polygons Intersect in python?

I'm looking for an algorithm, high level solution, or even a library which can help me determine if two polygons intersect, in Python. I have the vertices of the two polygons (These are single part ...
0
votes
0answers
67 views

Algorithm to find coordinates at selected intervals along a polyline?

I am developing an algorithm to search down a river at selected intervals and return the coordinates. See below: def Downstream(start, interval, data, offset=0, out=None): if out is None: ...
-1
votes
1answer
84 views

How to find the most east or west longitude around the date line

I've got a python script that is comparing extents of rasters in various projections. Generally it works, but sometimes, especially when the rasters are global in extent or cross the dateline it ...
2
votes
3answers
664 views

Efficient algorithms to split and join lines?

Referring to the Figure below: How to efficiently join segments into lines? How to efficiently break lines into segments? The above will be applied million times.
2
votes
1answer
274 views

Intersection of convex polygons on a spherical surface

There are a number of algorithms available for the intersection of two convex polygons, but I am interested in an algorithm to find the intersection of two convex polygons on the surface of a sphere, ...
4
votes
2answers
430 views

Method for finding circle center points that cover an extent

If I have a geographic extent, is there any way to find all of the center points of all of the 5km circles that would be needed to cover the entire extent? I'm working with an API that will return ...
5
votes
1answer
644 views

Python: find a method to calculate the “inner centroid” (also known as labelPoint in arcmap) of a polygon

i am looking for a method to compute the X,Y coordinate of a inner point (also known as labelPoint in arcmap) of a (irregular) polygon. I am try to find a solution without the use of ArcGIS module ...
10
votes
1answer
526 views

How to visualize azimuthal data with uncertainties?

I am trying to make a figure showing azimuthal data with a different range of uncertainties at each point. This oldschool figure from a 1991 paper captures the "bowtie plot" idea that I'm aiming for: ...
6
votes
3answers
4k views

Splitting lines automatically at specific distances using ArcGIS Desktop?

I have a set of polylines which I need to split at varying distances from their starting points. In general, I'm looking for a something similar to the SPLIT function within the editor tool. There ...
3
votes
1answer
381 views

How Can I Calculate Time from Coordinate?

For my application I am searching for an API or an algorithm for clicking point time and time zone. I dont know how I can do this but after getting time I want to calculate giving coordinate sun ...
7
votes
1answer
194 views

Optimize GEOSGeometry's spatial operations by avoiding thread-safety checks

A ranking algorithm I'm developing for a Django webapp requires performing spatial operations (within, intersections, sym_difference, etc.) using a query against large number of geometry objects. ...
3
votes
2answers
162 views

How to bring polygons closer to a point?

I have some scattered polygons with a lot of space between them. I want to make a thematic map but all that white space doesn't look very good, so I want to bring the polygons closer to the center of ...
8
votes
3answers
4k views

Bilinear interpolation of point data on a raster in Python?

I have a raster that I'd like to do some point interpolations with. Here is where I'm at: from osgeo import gdal from numpy import array # Read raster source = gdal.Open('my_raster.tif') nx, ny = ...
12
votes
4answers
4k views

Clustering Trajectories (GPS data of (x,y) points) and Mining the data

I've got 2 questions on analyzing a GPS dataset. 1) Extracting trajectories I have a huge database of recorded GPS coordinates of the form (latitude, longitude, date-time). According to date-time ...
16
votes
1answer
4k views

How to divide a polygon into specific sizes using ArcGIS?

I have several thousand irregularly shaped polygons in a shapefile. I want to be able to split each polygon into three areas, and to specify what the size of those areas (they sum to the previous ...