hjp@usenet.umr.edu (Hardy Pottinger) (07/26/90)
Does anyone know the format of dimeco data from the bureau of census? In particular, I'm looking for the map transform used. I've been using the data but I don't know the format of the coordinates. It's not longitude/latitude or UTM that I can tell. I need to merge it with some data in UTM coordinates or it wouldn't be particularly important. -- Dr. Hardy J. Pottinger / ___ 315 Engr. Res. Lab, UM-Rolla, Rolla MO 65401 _/__/__/ Voice: (314) 341-4511 Internet: hjp@ee.umr.edu / /
paul@hpldola.HP.COM (Paul Bame) (07/28/90)
If this is the same Census data I have seen, you get two endpoints per record containing first the unprojected lat/lon and then the projected versions: lon1 Geodetic "From" Longitude (Radians, negative sign assumed) lat1 "From" Latitude (Radians) lon2 "To" ... lat2 x1 y1 x2 y2 The projected coordinates are supposed to be an Albers projection scaled to fit a 20x30" map. A good idea might be to re-project the lat/lon pairs so you *know* what projection and scale is being used. A suitable projection is the Albers (as originally used supposedly) as described in one of the "Gems" in Glassner's new book (I wrote the gem) and have posted code before. Another person here in comp.graphics recently posted the updated version of the book from which I got the algorithm. You may also need a UTM <==> lat/lon converter which I'd like to collect as well. Shouldn't be too hard to write but I lost my UTM references years ago (ROTC map class believe it or not). -Paul "Spice is the Variety of Life" paul@hpldola.hp.com N0KCL 719 590 5557