Mike:
Standing Trees: You need diameter breast height (DBH) and merchantable height (# of 16-ft logs).
Logs: You need diameter inside bark (DIB) at the small end of the log and you need log length (ft).
Based on the data you collect, you can easily determine gross board feet of a standing tree or log using an infinite number of published volume tables found throughout cyberspace.
For example, here is a great publication from Purdue University:
http://www.extension.purdue.edu/extmedia/FNR/FNR-191.pdf
