Pete Templin wrote:

Very rusty memory cells on this, but I think the mileage is 0.1 * sqrt ((delta-V)^2 + (delta-H)^2)). That's assuming same LATA, IIRC.

Close. It's sqrt ( 0.1 * ((delta-V)^2 + (delta-H)^2)) ) and it doesn't care about LATAs. It's mostly accurate in the US middle 48 states and nearby parts of Canada and Mexico. http://datec.web.att.com/faqs/telecom.htm has more information, not all of it correct. Telecordia has pictures http://www.trainfo.com/products_services/tra/vhpage.html and will sell you more documentation and software, though they don't seem to make it easy :-) They've also got some material on issues with the newer coordinate systems such as WGS-84. Several other people all sell it - most of it's bundled with databases of NPA-NXX. http://article.gmane.org/gmane.comp.gis.proj-4.devel/26 points to the free OpenMap software, which has a converter. http://article.gmane.org/gmane.comp.gis.proj-4.devel/19 has Fortran code! Google will tell you more. ---- A long, long time ago, in a phone company far, far away, I worked with some people who decided they had to go reconstruct the algorithms used to generate these coordinates, and we had some programs that could calculate translations. Any records I have on that were probably backed up on a 9-track tape somewhere before the department moved to another building, though it's possible that they still exist on an account I no longer have access to on a machine that does still exist but is no longer as cutting-edge as it was in 1993.