Sunday, March 22, 2009
Saturday, March 21, 2009
Non-relational Databases
Came across this term though. I have heard of XML-databases. These are really different.
Mongo DB - Schema-free, document-oriented data store. Written in C++
Apache CouchDB - document-oriented data store.
Drizzle DB - Optimized for cloud and NET application
Wednesday, March 18, 2009
Map Technology
The world of map technologies is really dazzling ...
One of the leaders (if not the leader) is Refractions Research. Their open-source products are incredible -
Geoserver - a map server that dishes out maps in various projects, style and overlapping layers. It supports open standards for map delivery such as Web Map Service (WMS) and Web Feature Service (WFS). WFS provides more functionality for querying the features of the map such as features within an area and changing the styling. Styling is defined in an open standard, Styled Layer Descriptor (SLD).
uDig - A eclipse desktop client for map development. Loads most map file formats and provide styling capability.
PostGIS - A spatial database
Another comparable open source product to uDig is OpenJUMP.
On the client side, there is DeepEarth, a silverlight-based user interface for map navigation. Supports tiling, panning, zoom, search, pins, geometry and various map sources (e.g. Virtual Earth, Google Maps, Yahoo Maps, WMS)
Typically, the client side uses at least 4 coordinate systems:
Map projections are extremely important. Earth is round, but on the screen, it is flat. Here is a list of spatial references.
In the commercial world, there is TatukGIS.
Other map providers include PTV AG.
A popular file format for maps are ShapeFiles (*.shp)
For more information on tiling system, here is an article from Microsoft for Bing Map
All this in a span of 2 months.
One of the leaders (if not the leader) is Refractions Research. Their open-source products are incredible -
Geoserver - a map server that dishes out maps in various projects, style and overlapping layers. It supports open standards for map delivery such as Web Map Service (WMS) and Web Feature Service (WFS). WFS provides more functionality for querying the features of the map such as features within an area and changing the styling. Styling is defined in an open standard, Styled Layer Descriptor (SLD).
uDig - A eclipse desktop client for map development. Loads most map file formats and provide styling capability.
PostGIS - A spatial database
Another comparable open source product to uDig is OpenJUMP.
On the client side, there is DeepEarth, a silverlight-based user interface for map navigation. Supports tiling, panning, zoom, search, pins, geometry and various map sources (e.g. Virtual Earth, Google Maps, Yahoo Maps, WMS)
Typically, the client side uses at least 4 coordinate systems:
- Tiling (position of tiles, number of tiles)
- Geographical positions (most commonly used is latitude and longitude)
- Logical positions (from 0 to 1)
- Pixel positions (X and Y from a reference point which is usually the top left corner of a tile)
Map projections are extremely important. Earth is round, but on the screen, it is flat. Here is a list of spatial references.
In the commercial world, there is TatukGIS.
Other map providers include PTV AG.
A popular file format for maps are ShapeFiles (*.shp)
For more information on tiling system, here is an article from Microsoft for Bing Map
All this in a span of 2 months.
Tuesday, March 3, 2009
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