Hi David Five possibilities I can think off. First one is are you packing the table after doing the thinning? A pack should make it smaller as it removes deleted records. When you thin record 1 it becomes say record 1211001 but record one stays there until the geometry block is again changed.
More likely is that the projection of the original table has different bounds to the one that you save to. For example if you were thinning say Meridian or Oscar , and the original was unbounded. If you then save to bounded ( eg (0,0) (2000,2000) km ) then more geometry will be stored as 4 byte long ( rather than 2 byte short ) so the size of the file could go up. A third point is that because it is likely each segment of road begins and ends at a link, they might be quite short segments and therefore the percentage of nodes removed might be quite small. A fourth point is that the physical number of records will not change. Therefore the spatial index will be the same size, and if you did not pack could be bigger. The "save copy as" would effectively do a pack, so perhaps you are using tighter bounds? The fourth possibility is that the original tables were not created with MapInfo technology. For example the data provider might have used Safe Software. When creating the Map File there is a "redundancy" in the storage. This is actually beneficial as you can insert new records quickly into this redundant space. When you actually fill a partition it actually has to be split and at this time two new partitions that are only just over 50% full are created - hence on these two almost 50% redundancy. Your source data is expected to be read only and perhaps some other technology eg Safe has removed a lot of this redundancy. Good for read only , but not so good if you were inserting new records into the MAP file. Files created and packed by MapInfo typically have 25% redundancy. Regards Bob www.mapsbydesign.co..uk >All, > >There are some strange goings on inside my computer that I find hard to >understand...can anyone help. > >In the course of my daily grind I have found it necessary to generalise a >dataset of polylines that represents a road network. This particular dataset >is quite heavy and at the scale I am printing it the detail is not >important. So I am using the Object > Snap/Thin tool in MapInfo to thin down >the number of nodes in the network. > >That done my network is generalised, so I save the table, pack it, close it >and have a look at the file size in explorer.... > >...would you believe that despite removing detail from the MAP file by >generalising the network the *.map file is marginally bigger than the >original?! Can anyone explain this one for me, it seems a little backward? I >have tried this with several different networks of differing detail and >geographical spread with the same result. > >Also, in the process of this task I have noticed that using the 'Save copy >as' feature also creates a set of files where the *.map file is bigger than >the original...despite it being a COPY? > >If someone could shed some light on these weird occurrences, my Wednesday >afternoon would not have been in vain! > >Many thanks, Dave > > >This email and any attached files are confidential and copyright protected. >If you are not the addressee, any dissemination of this communication is >strictly prohibited. Unless otherwise expressly agreed in writing, nothing >stated in this communication shall be legally binding. -- bob young --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 15978
