Filed under Java

Free the Java Duke now and use it in Blender!

Duke, the Java mascot is a well known ambassador for Java. It is so important even Oracle still has a prominent site for it. The only problem is that the original source files can only be opened with a commercial application called lightwave3d. For GraphHopper I took those files and created an OpenStreetMap variant with … Continue reading

Setup Mapnik From Scratch

THIS document is a work in progress. There are several options but mainly three web map servers (WMS): Mapnik, GeoServer and MapServer. Simple visualization: A) browser/client (leaflet, openlayers) | B) tile server (mod_tile, tile cache, tile stache, mapproxy, geowebcache) | C) map web service = WMS (MapServer, GeoServer, Mapnik) | D) Data storage (PostgreSQL, vector … Continue reading

Java on iPhone or iPad

What options do I have to make my Java application working on the iPhone? It should not be necessary to jailbreak the phone. Also UI is not necessary for now although e.g. codenameone seems to support it. My application it not a complicated one, but uses Java 1.5 (generics etc) and e.g. memory mapped files. … Continue reading

Make Your Dijkstra Faster

Today I did a bit of research for GraphHopper and I stumbled over yet another minor trick which could speed up the execution of the Dijkstra algorithm. Let me shortly introduce this shortest path algorithm: If you need the path (and not only the shortest path tree) you will give the method an additional toNode … Continue reading

Failed Experiment: Memory Efficient Spatial Hashtable

The Background of my Idea The idea is to use a hash table for points (aka HashMap in Java) and try to implement neighbor searches. First of all you’ll need to understand what a spatial key is. Here you can read the details, but in short it is a binary Geohash where you avoid the memory … Continue reading

Spatial Keys – Memory Efficient Geohashes

When you are operating on geographical data you’ll use latitude and longitude to specify a location somewhere on earth. To look up some associated information or if you want to do neighborhood searches you could create R-trees, quad-trees or similar spatial data structures to make them efficient. Some people are using Geohashes instead because then … Continue reading