10. Accuracy, error and problems in forest measurement

Anon. 1983. Mensurational Problems of Forest Inventory in Southeast Asia. Proceeding of BIOTROP Symposium on �Mensurational Problems of Forest Inventory in Southeast Asia�, 26-28 June 1980. BIOTROP Special Publication No. 19, BIOTROP.

Included the paper presented and discussion of the seminar on Mensurational problems in forest inventory.

Gertner, G; Köhl, M. 1992. An Assessment of Some Nonsampling Errors in a National Survey Using an Error Budget. In Forest Science, 38, ( 3), 525-538.

Abstract: Different error budgets are approximated for the First Swiss National Forest Inventory. An error budget displays the effects of individual errors and groups of errors on the accuracy of estimates. The goal of developing the error budgets was to account for the significance sources of errors that can be expected in the national survey. Sources of error included measurements error of quantitative and qualitative attributes, regression error, and sampling error. It was found in general thet the national survey system was not very sensitive to unbiased random errors but was sensitive to systematic measurement errors.

Hooser, Dwande D. Van & Chojnacky, David C. 1984. Tree Diameter Measurement At English and Metric Standard Heights: A Comparison. Research Paper INT-327. 6pp, United States Department of Agriculture.

The impact of measuring trees at 1.3m versus 1.37m heights above ground line is analyzed. The results indicate that the difference in diameter measurement taken at the two points average around 1%. The conversion equation from English to Metric is presented

Ker, J.W. 1951. A Test of the Accuracy of Tree Height Measurements Taken by Abney Level and Chain. 2pp, Faculty of Forestry, University of British Columbia, Canada.

The total height measured with Chain and Abney Level is compared with the exact height measured after felling trees. The error involved in the measurement of standing trees is indicated.

Lennertz, Ralph & Uebelhör, Konrad edit. 1988. Proceeding of the Seminar on �Application of Results of Forest Policy, 15-19 February 1988. Philippine-German Forest Research Inventory Project..

Describe about the Philippine-German Forest research inventory project, inventory data processing, use of inventory data for national forest, information potential of natural forest inventories with focus on Mensurational problem in forest inventory

Marten, Bertil. 1961. On the Precision of Estimates of Diameter Growth from Increment Borings. International Union of Forest Research Organizations, 13th Congress, Vienna, Austria, 1961.. 7pp, International Union of Forest Research Organizations.

The paper gives some indications about the precision in estimates of the diameter increment of a stem at breast height. Thirty seven sampling trees have been selected and the measurement is taken for 5 years

Powell, Mark H. 1999. Effect of Inventory Precision and Variance on the Estimated Number of Sample Plots and Inventory Variable Cost: The Noel Kempff Mercado Climate Action Project. Winrock International. (available at http://www.winrock.org/REEP/NoelKmpff_rpt.html.)

This paper looks at the effect of different levels of inventory precision and variance on the estimated number of sample plots and their associated costs in the Noel Kempff Mercado Climate Action Project in northeastern Bolivia.

Siipilehto, Jouni. 1999. Improving the Accuracy of Predicted Basal-Area Diameter Distribution in Advanced Stands by Determining Stem Number. In Silva Fennica, 33(4), 281�301. (available at Abstract: http://www.metla.fi/silvafennica/abs/sa33/sa334281.htm.)

This paper deals with the extent the accuracy of predicted basal-area diameter distributions (DDG) could be improved by means of stem number observations in advanced (H > 10 m) stands. The analysis is based on sixty stands of Norway spruce (Picea abies Karst.) and ninety-one stands of Scots pine (Pinus sylvestris L.) with Birch (Betula pendula Roth and B. pubescens Ehrh.)

Ståhl, G.; Ringvall A.; Gove, J.H. & Ducey, M.J. 2002. Correction for Slope in Point and Transect Relascope Sampling of Downed Coarse Woody Debris. In Forest Science, 48 (1), 85-92. (available at http://www.ingenta.com/isis/searching/ExpandTOC/ingenta?issue=infobike://saf/fs/2002/00000048/00000001&index=9&WebLogicSession=PN6Wxc1IN6CAIkZeLV2o|-6583967751972381362/-1052814329/6/7051/7051/7052/7052/7051/-1.)

In this article, the effect of sloping terrain on estimates in point and transect Relascope sampling (PRS and TRS, respectively) is studied. With these inventory methods, a wide angle Relascope is used either from sample points (PRS) or along survey lines (TRS). Characteristics associated with line-shaped objects on the ground are assessed, e.g., the length or volume of downed logs. In their basic forms, the methods only work in flat terrain, and thus bias is incurred under sloping conditions.