Try to google spatial indexing. --- Daniel Morissette <[EMAIL PROTECTED]> wrote:
> scumhampton wrote: > > Hi, > > > > I have to say I'm really impressed with mitab. > > > > I'm creating my own map renderer - much like MapX. > Primarily I will > > use Navteq Street data. > > > > Maybe you should have a look at MapServer > (http://mapserver.gis.umn.edu/), it does exactly > that and much more, and > it uses the MITAB library (part of GDAL/OGR) to > access MapInfo TAB files > directly. > > > The problem I have is with large data sets. > Currently my application > > loads an entire layer into ram at the start (e.g. > minor roads). This > > is not a problem for Luxembourg, but when I load > the whole of Europe > > into ram, as you can imagine, things start to > become an issue. > > > > I know loading all the data at once is not the > right thing to do - I > > only need to load the area that I am currenly > displaying. But how? > > How do I find the ID of the features that should > be displayed? I > > guess I need some sort of geospatial look-up > table. How does MapInfo > > do it - it must load from the file dynamically as > you pan. Is this > > possible with mitab - or would I need to create my > own special look- > > up table? > > > > The TAB datasets (specifically the .map file) > contains a spatial index. > The MITAB C API doesn't provide any way to use it, > but through the C++ > classes, you can use the > OGRLayer::SetSpatialFilter() method: > > http://ogr.maptools.org/classOGRLayer.html#a3 > > Daniel > -- > Daniel Morissette > http://www.mapgears.com/ > > > > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ------------------------ Yahoo! Groups Sponsor --------------------~--> Protect your PC from spy ware with award winning anti spy technology. It's free. http://us.click.yahoo.com/97bhrC/LGxNAA/yQLSAA/dkFolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/mitab/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
