On Friday 27 Jun 2008 23:32, Rony wrote: > jtd wrote: > > On Thursday 26 Jun 2008 12:30, Rony wrote: > >> observed from space and can be marked clearly in the satt. > >> images. This reduces the trouble of people having to manually > >> walk everywhere with a device in hand. A software that can > >> convert the optical pattern code into text, automatically adds > >> relevant content into the converted maps. Just my 2p. > > > > Extremely error prone. Read 1st para. > > It would be similar to maps.google.com images in mixed > mode....satt. and outline with text over it. At very close zooms > over small areas,
Wrong. Checkout Surat. > the curvature of the earth may be easy to > correct. Something like an areal photo from a spy plane. . > Its a wrong approach. You can use such a method as a rough guide only. There are numerous issues with the type of projections, proximity to the pole etc - rendering a sphere on a flat surface - apart from the problems with sat imagery. Basically the pixmaps you see are pre-rendered images from a geodatabase overlayed with satellite imagery, Out of which you are trying to create a GIS database. The process is not bidirectional. You MUST generate an accurate database for substantial areas to have useable data. BTW street maps are a minor part of a GIS system. Real use happens when you can overlay info like disease spreads, water sheds, insect vectors etc, etc. and come up with a basis to use these as predictors of problems. Then use these as guides to intervene. e.g mindless spraying of inseticide to prevent malaria in Mumbai and Navi mumbai. Is any body checking the effectiveness of such methods and how it is actually helping the mosquitoes by killing natural predators (who btw are several orders of magnitude more effective than ddt / malthion ). Being directed to the nearest dhaba by googlemaps is great but ensuring you dont get hepatitis-B on the house is proly a lot better. The point here is that mapping is a tedious affair. Shortcuts result in poor quality database which inevitably causes bitrot. Besides the copyright issues there are technical issues too - both rather difficult to solve. Make the extra effort to prevent bitrot and legal hassles. The FOSS approach is a perfect fit for GIS. -- Rgds JTD -- http://mm.glug-bom.org/mailman/listinfo/linuxers
