GRASS GIS manual: v.lidar.edgedetection v.lidar.edgedetection - Detects the object's edges from a LIDAR data set. vector, LIDAR, edges v.lidar.edgedetectionv.lidar.edgedetection helpv.lidar.edgedetection [-e] input=name output=name [see=float] [sen=float] [lambda_g=float] [tgh=float] [tgl=float] [theta_g=float] [lambda_r=float] [--overwrite] [--verbose] [--quiet] Flags: -e Estimate point density and distance Estimate point density and distance for the input vector points within the current region extends and quit --overwrite Allow output files to overwrite existing files --verbose Verbose module output --quiet Quiet module output Parameters: input=name Name of input vector map output=name Name for output vector map see=float Interpolation spline step value in east direction Default: 4 sen=float Interpolation spline step value in north direction lambda_g=float Regularization weight in gradient evaluation Default: 0.01 tgh=float High gradient threshold for edge classification Default: 6 tgl=float Low gradient threshold for edge classification Default: 3
Open Source Tool Sets for Creating High-density Maps A few weeks ago I wrote about some of the building blocks available to create engaging maps in Drupal . The module ecosystem around maps and other geospatial functionality is pretty flexible, but there are some situations where Drupal might not be the best fit. There are some great tools out there to build out sites when the situation calls for little else besides a map display, or when processing and rendering tens of thousands of geospatial features. In this blog post, I’m going to talk about two in particular, Mapbox and CartoDB . Mapbox Mapbox is a great map building tool that allows for the creation of pre-rendered mapping displays with a set of web-friendly tools. Styling maps in Tilemill is handled through a language called CartoCSS , which shares many syntax similarities to CSS and Sass. CartoDB CartoDB is a mapping stack that has many similarities to Mapbox. Like anything in life, there are tradeoffs. Real-word Mapping Example: Finding Apartments in NYC Step 1. Step 2. Step 3.
A Beginner’s Guide to pgRouting Please read the new instructions for pgRouting 2.0. The aim of this post is to describe the steps necessary to calculate routes with pgRouting. In the end, we’ll visualize the results in QGIS. This guide assumes that you have the following installed and running: Postgres with PostGIS and pgAdminQGIS with PostGIS Manager and RT Sql Layer plugins Installing pgRouting pgRouting can be downloaded from www.pgrouting.org. Building from source is covered by pgRouting documentation. Start pgAdmin and create a new database based on your PostGIS template. Creating a routable road network The following description is based on the free road network published by National Land Survey of Finland (NLS) (Update January 2013: Sorry, this dataset has been removed). First step is to load roads.shp into PostGIS. pgRouting requires each road entry to have a start and an end node id. Next, we create start and end point geometries. (This can take a while.) I recommend adding a spatial index to the resulting table.
Gephi makes graphs handly GFOSS - Free Software GIS at your fingertips Cartographica | The Macintosh GIS Drive Time Isochrones – An Example Using Finnish Airports Site analyses can benefit greatly from using “drive-time” isochrones to define the study area. Drive time isochrones are often significantly different from simple buffer areas which disregard natural barriers such as rivers or slow roads. Of course, creating drive time isochrones requires more input data and more compute-intensive algorithms than a simple buffer analysis. It is necessary to create a routable network graph with adequate weights to be used by the routing algorithm. One of the most popular routing applications in the open source world is pgRouting for PostGIS enabled databases. The first step is to find the closest network node to every airport: Then, we can calculate drive times between network nodes and “airport nodes”. Every following node is done with an INSERT: Afterwards, I combined the values to find the minimum drive time for each network node: The resulting point layer was imported into QGIS. Like this: Like Loading...
Natural Graphics PgRouting 1.02: Test de la fonctionnalité shortest_path_shooting_star() - Le blog de Jean David TECHER, un Réunionnais à Saint-Priest/Lyon Le descriptif de cette fonctionnalité est fournie à Cette fonctionnalité permet notamment de prendre en compte les sens de parcours. On peut si on veut dans la colonne _to_cost préciser si le coût de parcours du tronçon est fonction de la distance, du prix de péage etc... tar xzf pgRouting-1.02.tgz ; cd pgrouting; cmake -DWITH_TSP=ON -DWITH_DD=ON \ -DPOSTGRESQL_INCLUDE_DIR=/usr/local/pgsql/include/server/ -DPOSTGRESQL_LIBRARIES=/usr/local/pgsql/lib/ \ -DCGAL_INCLUDE_DIR=/usr/local/cgal/include/ -DCGAL_LIBRARIES=/usr/local/cgal/lib/ make make install Pour la création de la base avec les fonctionnalités adéquates On télécharge le fichier le fichier suivant wget psql routing -f reseau.sql Le contenu sera le suivant Quand sens = 'sens direct', celà signifie qu'on traverse un tronçon relatif à un rond-point J'aurais donc l'image suivante Fig 1. #! .
Shaded Relief – Home Project — Open Source Routing Library Installation on Ubuntu — Open Source Routing Library Install required packages sudo apt-get install build-essential git-core cmake sudo apt-get install postgresql-8.3-postgis postgresql-server-dev-8.3 If you’re not planning to install CGAL from Ubuntu multiverse, you can use default Boost library from the repository. This will be version 1.34 at the moment. sudo apt-get install libboost-graph-dev For Driving Distance sudo apt-get install libcgal* Note If you install CGAL later from Ubuntu multiverse it will upgrade to Boost 1.35. For TSP wget tar -xzf gaul-devel-0.1849-0.tar.gz cd gaul-devel-0.1849-0/ . Setup PostgreSQL Set local database connections to “trust” in “pg_hba.conf” to be able to work with PostgreSQL as user “postgres”. sudo gedit /etc/postgresql/8.3/main/pg_hba.conf sudo /etc/init.d/postgresql-8.3 restart