Using xv 3.10a (UNIX), "shareware for personal use" by John Bradley, the (x,y) pixel coordinates from the USGS DRG tiffs can be read by mouse anywhere on the quad.   There are similar capabilities with other imaging programs on a variety of platforms. o42093a6.tif 4944 Kb o42093a6.tfw 84 bytes Contents of the o42093a6.tfw is: 2.43840000 x resolution (2.4384 m = 8 ft) 0.00000000 amount of translation 0.00000000 amount of rotation -2.43840000 negative of the y resolution 437110.07786386 x ground coordinate of pixel 1,1 4664482.79159758 y ground coordinate of pixel 1,1 (1,1) +-----------------+ | | | | | | | | | | | | | | | | | | | | Pixel coordinates | + <------ 2825, 4300 translate to: | | 443998.58 (easting) | | 4653997.68 (northing) | | +-----------------+ My attempt to position the cursor on the UTM intersection of 444000 and 4654000 is off by a few meters, which is about as good as it gets with a resolution of 2.4384 meters (8 ft).   I doubt I could do better making measurements off of paper maps. When entering waypoints into your GPS receiver, make sure you are using the same GPS datum as that on the map or DRG!   Datum information is printed in the lower left-hand corner of USGS 7.5-Minute Quadrangle maps. HP-48 Program to convert back and forth from pixels to UTM Rn: 4664482.8 Re: 437110.1 Sc: 2.4384 DRG: << -> Pe Pn << IF 'Pe<100000' THEN 'Re+Pe*Sc' EVAL 'Rn-Pn*Sc' EVAL ELSE '(Pe-Re)/Sc' EVAL '(Rn-Pn)/Sc' EVAL END >> >>     © Copyright 2007 - Samuel J. Wormley   by swormley1@mchsi.com