-------- Original Message -------- Subject: Plat maps Date: Mon, 24 Nov 2003 11:27:33 EST From: <[log in to unmask]> ------------------ I work in a local history collection (District of Columbia) that contains plat maps (e.g., published by Baist or Sanborn). These maps were published approximately every 5-10 years for certain sections of the city, and are one of the collection's most prized and frequently used resources. Occasionally, a patron will ask about the publishers' methodology: did the surveyors collect information during the course of one year--the year of publication--or were the data collected over a number of years? For example, does the 1909 map reflect what was on the ground for 1909, or might it show what was actually there in 1907? Also, is there any consensus about the accuracy of one group of maps over another? Are the Sanborn maps considered more accurate on the whole? Any advice or information about these maps would be most appreciated. Margaret Goodbody Collections Librarian Washingtoniana Division, Rm. 307 MLK Library 901 G Street, NW Washington, D.C 20001