New Tools & Techniques in Forest Mensuration

Thomas E. Burk University of Minnesota

New Tools & Techniques in Forest Mensuration  Efficient timber stand assessments  Laser-aided measurement  Field data recording

New Tools & Techniques in Forest Mensuration  Efficient timber stand assessments  Laser-aided measurement  Field data recording

Timber Stand Assessment  Line plot cruises  Systematic layout of sample locations  0.1 acre or 10BAF plots  Measure every tree counted  Sample average estimator

Timber Stand Assessment  Double sampling  Systematic layout of sample locations  Count trees at all locations  Measure trees at every 2 nd , 3 rd , 4 th , or 5 th location  Ratio of means estimator

Timber Stand Assessment  Double sampling sample sizes  Measure versus count cost  Correlation (V, G)  Relative coefficients of variation of V and G Cost Ratio 2 4 6 2 4 6 Count Sample Ratio Measure Sample Fraction Cv Ratio = 1.0

1.2

0.50

1.5

1.7

0.29

0.22

Cv Ratio = 1.5

1.2

0.57

1.5

1.7

0.33

0.25

Timber Stand Assessment  Current practice deficiency summary  Too many trees counted per location  Too many trees measured  Tree measurement clustered

Timber Stand Assessment  For single or double sampling and variable radius plots:  Volume/ac = G * VBAR  G comes from counting, VBAR comes from measuring  Relative variability should dictate how much we count versus how much we measure

Timber Stand Assessment  Big BAF sampling  Count and measure at every location  Count with a “small” BAF instrument  Measure (select trees for measuring) with a “big” BAF instrument

Timber Stand Assessment

Timber Stand Assessment

Timber Stand Assessment  Big BAF instrumentation  Small BAF giving ~ 5-8 counts per plot  Large BAF giving ~ 1 measure per plot  Can be formalized  Caveats  Big BAF sample size  More total plots than standard methods  G is crucial

Timber Stand Assessment  Separate measuring and counting  Measure fewer trees (more accurately) and spread them around

Take Home

 With variable-radius plots, height is the key measurement  Count more trees by using more locations  G is crucial

New Tools & Techniques in Forest Mensuration  Efficient timber stand assessments 

Laser-aided measurement

 Field data recording

Laser-Aided Measurement

Laser-Aided Measurement  Tree attributes  Basic surveys  Supplementing GPS

Laser-Aided Measurement Tree Height Horizontal Distance Base Angle Top Angle Height

Laser-Aided Measurement Tree Height  Advantages  “Free-to-choose” line of site  Scope provides better sighting  Multiple trees from single location  Good inherent accuracy

Laser-Aided Measurement Tree Diameter 0 20 40 60 80 100 10 30 50 70 90 

Horizontal distance



Base angle



Height to diameter



Reticle reading



Diameter

Laser-Aided Measurement Basic Surveys  Traverses  Slope and horizontal distance  Simultaneous compass work  Point-to-target  Boundaries  Navigation

Laser-Aided Measurement Supplementing GPS  GPS advantages  Eliminates long control traverses  Moderate to high accuracy  Digital output in absolute geographic coordinates

Laser-Aided Measurement Supplementing GPS  GPS disadvantages  Inefficient for recording large number of features  Sight limited under forest conditions  Bulk

Laser-Aided Measurement Supplementing GPS

Laser GPS

Laser-Aided Measurement  Interface to data recorder  Extend internal storage  Interoperate with other software/hardware

Laser-Aided Measurement

Take Home

 More convenient and careful measurement often warranted  Cost/benefit needs careful attention

New Tools & Techniques in Forest Mensuration  Efficient timber stand assessments  Laser-aided measurement 

Field data recording

Field Data Recording  Advantages  Ease of entry  Error/consistency checking  Processing  Integrated (with) measurement technology

Field Data Recording  Popularity?

 Needs versus capability  Programming  Investment  Seamless information system solution  More information  FORS Compiler  JofF Buyer’s Guide

Field Data Recording – Rethinking the Options   Generic software solutions “Swiss Army Knife” hardware capability  Smaller form factor  Wireless communication  No frills system integration

Field Data Recording – Rethinking the Options

Field Data Recording – Rethinking the Options

Field Data Recording – Rethinking the Options

Field Data Recording – Rethinking the Options

Field Data Recording – Rethinking the Options  GIS in the field  Customized products based on digital, multi spectral, high spatial resolution satellite imagery  Measurement augmentation

Field Data Recording

Take Home

 Full system solution  Start small  Think generic and multi purpose

Evaluating Technology  Costs versus gains in quality, timeliness, and usability of data  Importance of decisions requiring information derived  Support for change throughout organization