This pretty much sums it up. I guess I'll have to re-geocode it all. Thanks for all the replies and the utilities.
Cameron "Bagwell, Ross" wrote: > Taken from a previous email to the List from Tom Kay 8/18/2001: > > The V&H coordinate system was/is a very imperfect formula that, when > combined with the source of information fed into > it by the LECs becomes a severe nightmare. > > LERG (Local Exchange Routing Guide) > > A brief history of the system as used in the LERG: It was developed back in > the '30s from an algorithm originally > created in the 1500s by one of our ancient navigators (Magellan?), and only > intended to work for telco purposes > the continental United States. By virtue of the size of the base grid, a > little bit of Southeast Alaska, parts of > Canada, Mexico and some of the Carribean islands fell inside and could > return 'correct' V&H for a few switches in those > areas by default. The design was intended only for the United States as > that was where Ma Bell operated, they had no intent or need for the system > to work anywhere else. > > The system's design was to determine toll distances (miles) between any pair > of switches, thus creating a base to determine your long distance charges. > (Some of you really get shafted). The system was not designed for mapping > purposes. > > In 1994 Bellcore (now Telcordia "http://www.telcordia.com/";) published and > sold a set of computer programs to convert > LL/V&H it may be available still, I have no need for it anymore so didn't > look for it at the link above.) > > Bellcore was renamed Belllabs and then subsequently became Telcordia since > the "Bell" name couldn't be used. Telcordia is currently owned by Science > Applications International Corporation (SAIC). > > Many hundreds of the VH entries (in the LERG) are very inaccurate, > frequently the LEC didn't know the coordinates (lat/lon) for a particular > switch so they 'borrowed' coords from something near-by and submitted that > to the LERG database via what was called the CLONES system (computer). Many > other errors too are introduced with typos and other errors such as reversed > input (V in the H and H in the V type errors.) > > To derive the greatest accuracy possible for mapping switch (device) > locations, one should geocode the LERG using > MapMarker plus on the street addresses and V&H on any entry that does not > include a geocodeable address. (This can be > done by merging LERG 1, 6 & 7 together) to put all of the relevant data > together. It is a rather cumbersome task, but > if you need any level of accuracy it's the best way to do it. Though you'll > still have hundreds of errors. > > Consider that the VH system was developed without modern day computers (we > had none when it was originally created) so it was the best thing available > for the task. With today's GIS capabilities and computer system Bellcore > should have converted their system to accept decimal degree lon/lat data > instead of continuing to use V&H, or at the very least, > include two columns for the original Lat/Lon pairs so that we could map them > from the original source data. I approached Bellcore in 1994 about the > practicallity of changing that system to dec degrees, my plea fell on deaf > ears, but then 'it was they way they'd always done it', a 'legacy' system > and their interest is not for mapping purposes. > > When one converts LL to VH the result will have an error, guaranteed. It > goes without saying that if you then convert > your resultant V&H pair back into lat/lons, you'll have another error. > > In short you will not get reliable precision from LERG data, at best you'll > get close, if you need precision you can best accomplish it through > development of MapBasic programs, database (LERG) merges and MapMarker+. It > isn't too painful if your interest is in a small geographic area of the U.S. > but for all telco switches & devices in the U.S., plan on an initial > investment of a few hundred hours (program development and initial mapped > results 'validation' to correct everything possible, and then a few hours > each month to update your maps from LERG monthly updates. > > FYI... LERG data is a subset of Telcordia data. > > -Ross E. Bagwell > GIS Manager > Universal Access Inc. > > -----Original Message----- > From: Cameron Crum [mailto:[EMAIL PROTECTED] > Sent: Wednesday, March 05, 2003 12:51 PM > To: [EMAIL PROTECTED] > Subject: MI-L Telephone Company Coord system > > I have a Telcordia(sp?), formerly Bell Labs I think, database of > central offices for the US that have the fields v-coord and h-coord. The > entries in these fields are a four digit number. Does anyone happen to > know what coordinate system they might have used? Maybe some of the guys > with a little wireline telco experience out there? > > Cameron > > --------------------------------------------------------------------- > List hosting provided by Directions Magazine | www.directionsmag.com | > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > Message number: 5798 > > This communication contains information from Universal Access, Inc. 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