I've been watching this thread over the past day and I guess my question is this: Do we, as GIS professionals, have any options to the ESRI Shape/MapInfo TAB format debate? Is there a published format for storing spatial data that has a reasonably efficient spatial index? Do we, as consumers of the technology, (and I'm not just talking about MapInfo here) push the demand for a format that meets our needs and is also open? Is there now a need to implement some of the features we as users have wanted to see for some time (ie. compression, encryption)?
I am constantly impressed at the expertise of the individuals on this list. To propose and implement a spatial format that would be open and extensible could be huge for our industry! Is there anyone else out there that would like to see such a thing as well? - Ian Erickson ----- Original Message ----- From: "Warren Vick, Europa Technologies Ltd." <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Friday, February 06, 2004 4:11 AM Subject: RE: MI-L UK OS MasterMap - Can't work with ESRI .shp files? Hi Bob, With SHP vs. MIF/MID, it's not so much a preference but a industry observation. The formats that organisations use to share data is largely down to the platform they have chosen and we all know that MapInfo is strong in some areas an ESRI in others. The change is use of Shapefiles has changed my view of GIS formats as I believe it blurs the distinction between separate "use" and "export" formats. Of the technical merits, MIF/MID was obviously designed to be simple to read but cannot be reasonably used for viewing. I think perhaps the number of people reading MIF/MID in their own code might be outweighed by the number who would find it useful to view an export format directly. Reading the open-spec parts of SHP (and flipping integer endian) is not difficult, and is certainly faster than parsing text. As for local UK authorities, I've no idea simply because I've never worked in this area. I certainly know people I can ask and will follow-up. It's perhaps more important to acknowledge that UK local government is only a small piece of the global GIS pie and there are plenty of other applications managing large data sets. On the desktop, TAB may well have some advantages over SHP, but ESRI is the second largest private software company in the world - I suggest they would not be in that position if they did not have the technology to handle large data sets! Regards, Warren Vick Europa Technologies Ltd. http://www.europa-tech.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: 06 February 2004 10:29 To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: RE: MI-L UK OS MasterMap - Can't work with ESRI .shp files? 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 --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 10301 --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 10307
