Error assessment for a provincial timber inventory

1995 ◽  
Vol 71 (5) ◽  
pp. 627-632 ◽  
Author(s):  
János Gál ◽  
Imre E. Bella
Keyword(s):  
Computer Simulation ◽  
Simulation Experiment ◽  
Sampling Error ◽  
Measurement Bias ◽  
Error Assessment ◽  
Volume Estimate ◽  
Computer Simulation Experiment ◽  
Volume Estimates ◽  
Timber Inventory

In this case study of the Saskatchewan provincial timber inventory, the major sources of errors were identified and suitable procedures presented for their estimation. Applying those procedures on a pilot area, the results showed that sampling error was by far the most important component affecting the accuracy of volume estimates. Variances arising from the use of taper functions to estimate tree volumes were under 0.05%, and variances from 3P subsampling were about 3% of the total variance. A computer simulation experiment showed that a 2% measurement bias in both diameter and height measurements may result in 8% bias in the volume estimate. Key words: 3P sampling, taper functions, error budget

Comparison of quasi-linear predictions with a computer simulation of whistler waves in unstable plasmas

1974 ◽  
Vol 11 (3) ◽  
pp. 397-401 ◽  
Author(s):  
S. Cuperman ◽  
L. R. Lyons
Keyword(s):  
Growth Rate ◽  
Computer Simulation ◽  
Distribution Function ◽  
Mode Coupling ◽  
Simulation Experiment ◽  
Electron Distribution Function ◽  
Linear Wave ◽  
Wave Growth ◽  
Whistler Mode Waves ◽  
Computer Simulation Experiment

The quasi-linear concept of plateau formation along resonant diffusion surfaces is compared with the time evolution of the electron distribution function during a computer simulation experiment of whistler-mode waves in unstable plasmas. It is found that, as the wave intensities grow, plateau formation does indeed occur, with the distribution function becoming constant along diffusion surfaces at the time when wave intensities maximize. Following the formation of the plateaus, both the wave intensities and the slope of the distribution function along diffusion surfaces oscillate in a manner suggesting msh;mode coupling. Tbe slope of the distribution function along diffusion surfaces, which controls the linear wave growth rate, also gives good predictions of the sign of the actual wave growth rate during the experiment.

scholarly journals Stratified Light Detection and Ranging Double-Sample Forest Inventory

2007 ◽  
Vol 31 (2) ◽  
pp. 66-72 ◽  
Author(s):  
Robert C. Parker ◽  
David L. Evans
Keyword(s):  
Forest Inventory ◽  
Sampling Error ◽  
Phase 1 ◽  
Sample Volume ◽  
Light Detection And Ranging ◽  
Phase 2 ◽  
Light Detection ◽  
Volume Estimate ◽  
Individual Tree ◽  
Volume Estimates

Abstract An industrial application of a light detection and ranging (LiDAR) individual-tree, stratified double-sample forest inventory of approximately 18,000 ha of southeastern pine plantations was accomplished with an 9:1 ratio of 0.02-ha phase 1 LiDAR and phase 2 ground plots in ages 6 to 28 years. Phase 2 ground inventory data of tree dbh and sample tree heights for 2 trees per plot were used to obtain dbh-height relationships and volumes of standing trees. Phase 1 LiDAR data with 1.9 points per m2 were used to obtain ground–LiDAR height relationships for phase 2 matching LiDAR trees and phase 1 estimates of basal area and volume. A conventional ground inventory of 971 ground plots by private contractors applying standard company field specifications resulted in an overall sampling error of ±2.7% (α = 0.05) for a single-phase volume estimate and ±2.2% for the double-sample volume estimate. Sampling error was defined as one-half the 1-α confidence interval expressed as a percentage of the mean. Reducing the phase 2 ground sample to 15 plots per age class stratum achieved sampling errors of approximately ±15% for half the strata, with a combined error of ±3.9%. Adjusting the LiDAR-ground height bias of approximately 1.8 m resulted in more realistic volume estimates compared with the industry's continuing forest inventory volumes. The double-sample volume estimates were obtained at a cost of approximately $3.88/ha of timberland inventoried as compared with $1.67/ha for the conventional inventory.

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