Hi Warren I'm surprised you would suggest using SHP and SHX for data interchange by preference.
MapInfos MID/MIF is of cource only designed for data interchange and not for viewing ( so no need for a spatial index). Just like XML, GML and Auodesks DXF it is an ASCII format and so can be easily viewed on any platform and can virtually be understood with no documentation. However SHP/SHX is binary. Further Unix and Windows platforms store their 4 byte integers in a different order making SHP less suitable for data interchange. I cannot see why you would want a spatial index on a format designed for data interchange. I am really interested in the new ESRI formats that you mentioned. Are you aware of any reasonably sized local authority that is using these new desktop formats to view MasterMap? Personally I am convinced that MapInfos 18 year old format is a big advantage for local authoritys and that this is being underplayed. The public at large here is unhappy that council taxes are rising at rates between 10% and 20%. Their budgets are important and it hurts to see them spending money unnecessarily. Regards Bob Quoting "Warren Vick, Europa Technologies Ltd." <[EMAIL PROTECTED]>: > Hello all, > > As Uffe has mentioned, the performance of shapefiles is not bad at all, as > long as a spatial index is built. Unlike MapInfo TABs, it's not > automatically built and maintained. Perhaps due to the closed format of the > spatial index, no translator I'm aware of (including UT and it's bigger > brother FME) have an option to build it. A shapefile of any reasonable size > *must* have the index built unless you want to be hanging around for > redraws > and other spatial DB operations. > > As I mentioned to Bob in a direct e-mail, the other thing to consider is > that shapefiles are quickly becoming more of an interchange format as ESRI > moves on with other technologies (both server and desktop). These implement > topology, multi-user editing and very high-end compression plus many other > features that many MapInfo users would love to see without moving up-scale > on their DBMS. Already, if not in the near future, a more accurate > side-by-side comparison will be between shapefile and MIF/MID - the latter > having no option of a spatial index at all. > > Regards, > Warren Vick > Europa Technologies Ltd. > http://www.europa-tech.com > > -----Original Message----- > From: Uffe Kousgaard [mailto:[EMAIL PROTECTED] > Sent: 05 February 2004 21:04 > To: [EMAIL PROTECTED] > Subject: Re: MI-L UK OS MasterMap - Can't work with ESRI .shp files? > > > Hi Bob, > > There is no doubt that TAB is a better format than SHP, but SHP isn't that > bad. Based on your description below, it seems like you are not using the > spatial index files (SBN+SBX) of the SHP format. If you use them, arcview > can actually redraw at a pretty decent speed without reading the whole SHX > or SHP file. > > SBN+SBX files are closed format as opposed to the SHP+SHX files. > > Kind regards > > Uffe Kousgaard > www.routeware.dk > > > From: <[EMAIL PROTECTED]> > > > > With the native SHP,SHX file format the data is NOT rearranged so that > > objects adjacent on the ground are adjacent in the file. Every single > > MBR in the SHX file has to be compared with the Screen MBR. If it is > > on the screen then the full object contained in the SHP file will > > again be stored randomly ( stored in order added ) and disk access > > will be relatively slow compared to MapInfo as the heads will be > > jumping around rather than reading contiguously. So the whole SHX file > > needs to be read, if there are 4 million objects every MBR has to be > > read, and then the 200 on the screen will need to be read in full > > randomly ( rather than contiguously ) from the SHP file. > > > --------------------------------------------------------------------- > List hosting provided by Directions Magazine | www.directionsmag.com | To > unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > Message number: 10290 > > > > > --------------------------------------------------------------------- > List hosting provided by Directions Magazine | www.directionsmag.com | > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > Message number: 10294 > > --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 10300
