FNR-108
forestry & natural resources
WOODLAND MANAGEMENT 
CRUZ—A Timber Volume Estimation Program for the HP-41C*
by Thomas W. Beers, Department of Forestry and Natural Resources
The availability of convenient and powerful handheld programmable calculators, such as the Hewlett-Packard 41-C, promises to have a significant impact on most of the scientific community. In fact, the applicability of such calculators to the field of forestry, in general, and to forest inventory, in particular, is enormous.
This bulletin presents and describes CRUZ—a program for the HP-41C—to show how routine forest inventories can be readily processed on this relatively inexpensive calculator instead of through laborious handwork. Although other programmable calculators are capable of forest inventory programming, the HP-41C is chosen for the sake of example and convenience.
CRUZ is a program to process inventory data from fixed-size sample plots or from a horizontal point sample. The primary motivation in writing CRUZ is to demonstrate the capabilities of the HP-41C calculator. CRUZ is a complex and somewhat specific program. The user is therefore encouraged
to adapt various aspects of CRUZ to his particular needs, rather than expect it to be immediately applicable for him.
For those not familiar with the features of the HP-41C, it should be noted that its continuous memory feature and very long battery life suggest the feasibility of direct tally of tree data into the calculator, therefore eliminating the pencil-paper recording operation. The system is not foolproof yet, and users are urged to apply CRUZ to the situation where field data have been recorded on paper and an on-the-spot, or at least very timely, summary is needed. Obviously, for large forest inventories, the use of computer processing is desirable and frequently justified.
Following are five aspects involved in the use of CRUZ—a general description; the program procedure; typical data and two examples; storage register assignments; and a program listing.
* This publication is the second in a series of two on the use of programmable calculators in forest management. The first is entitled, FNR-107 “APPRAZ—A Timber Volume Estimation Program for the HP-41C.”
PURDUE UNIVERSITY • COOPERATIVE EXTENSION SERVICE • WEST LAFAYETTE, INDIANA 47907