FOREST MEASURement
EC 1129 • Reprinted September 2008 $2.00
Tools for Measuring Your Forest
S. Bowers
Contents
The tools and how they work.......... 1
Angle gauge................................. 1
Clinometer.................................... 1
Combination logger's tape.............. 2
Compass...................................... 2
Global Positioning System (GPS)..... 2
Increment borer............................. 2
Log volume tables......................... 3
Pacing......................................... 3
Rangefinder.................................. 3
Topographic map........................... 3
Tarif access tables.......................... 3
Tree volume tables......................... 4
The Woodland Stick....................... 4
Comparing tools............................ 4
For more information......... back page
W
oodland owners routinely want to measure property acreage,
boundaries, ground slope, various characteristics of standing
timber, and
individual log volumes.
Different tools are
required for each of
these tasks (Figure 1).
Forests and forest products can be
measured efficiently
and precisely with
sophisticated, and often
expensive, instruments.
However, most measurements can be made
with a few simple and
inexpensive tools.
This publication
discusses only those
Figure 1.—Tools you’ll use for some measuring
tools that are readily
tasks are (clockwise, from top left) a clinometer, a
available, affordable,
compass, an increment borer (with flagging tape
and appropriate for a
attached, to make the borer easier to find if it falls
woodland owner who
on the ground), and a combination logger’s tape.
has basic measurement
skills. Table 1 (page 5) compares the accuracy and convenience of each
type of tool for taking certain measurements.
The tools and how they work
Steve Bowers, Extension forester,
Lane and Douglas counties,
Oregon State University.
Angle gauge A mechanical or optical device for measuring basal area
of trees in variable-plot sampling; that is, sampling a plot containing trees
of various sizes. The most common is a wedge prism, a precisely ground
glass wedge that is calibrated in basal area factors (BAF) from 10 to 70.
Most woodland owners use a prism with a BAF scale between 20 and 40.
Average tree diameter and prism BAF are directly proportional—as average tree diameter increases, prism BAF increases also.
Clinometer A rugged, hand‑held instrument for measuring vertical
angles such as ground slope, road grade, and tree height (Figure 2).
Various models have degree and percent scales, percent and topo scales,
or degree and topo scales.
Global Positioning System (GPS)
Recommended models
This is a general term that refers to variinclude those containing
ous hardware and software used to locate
the degree and percent
certain points on the earth, such as propscales. When using the
erty and unit boundaries, acreages, roads,
degree scale, at a distance
and elevations (Figure 5). GPS technology
of 100 feet from the tree,
uses a receiver and a data logger to capture
heights can be measured
and interpret electronic signals transmitted
directly, and slope is an easy from satellites that orbit the earth. Location
can be determined very accurately through
Figure 2.—The clinometer has calculation.
Combination logger’s
GPS, but accuracy depends on the quality
a sighting hole and a susof the receiver, satellite reception,
pended circular scale that can tape A steel tape with a
measure ground slope as well spring/spool rewind contain- topography, canopy cover, and other facing measurements in various tors. In forests, canopy cover may interfere
as tree height.
combinations on both sides
with satellite reception and make it difficult
of the tape. The recomto take reliable measurements.
mended tape has tree diameter in inches
Increment borer This is a handon one side, and the other side measures
operated drill with a hollow bit that extracts
length in feet and inches (Figure 3).
Standard tapes come in 50-, 75-, and
100-foot lengths. The 50-foot tape
is recommended for use in logging,
but if you are going to use the tape
exclusively for tree measurements,
the 100-foot tape is best.
Compass A hand‑held compass
is a relatively rugged instrument
that measures horizontal angles
or direction in degrees (Figure 4).
Compasses are used most often
when following transect lines to
establish plots for timber measurements or cruise estimates and in
determining boundary or property
lines. Placing the compass on a
solid, nonmetal object can give
Figure 4.—Hand
more precise readings. Compasses
compasses such as
are available in azimuth (0° to
this typical model
360°) or quadrant (0° to 90°). Most
are used to measure
woodland owners find the azimuth
horizontal angles.
easier to use.
Figure 3.—A combination logger’s tape can measure tree diameter (above left) in addition to
log lengths and diameters (above right).
2 THE WOODLAND WORKBOOK
a wood core from the
stem of a tree (Figure 6).
Figure 5.—
Wood core samples are
The cost of
a GPS unit
used in determining tree
ranges widely,
growth, age, and general
from a few
health. Borer length varhundred dolies in 2-inch increments,
lars to several
from an 8-inch minimum
thousand. Less
to a 16-inch maximum
costly handsampling depth. The largheld models
est is adequate for conveare used for
niently determining the
hiking and
age of trees up to about
hunting as
30 inches in diameter
well as for forestry applications such as riparian
(including bark). Most
and timber boundaries. More precise measurewoodland owners use the
ments involving legal descriptions or property
8-, 10-, or 12-inch borers.
boundaries require trained and licensed individLog volume tables A
uals using expensive GPS units. High-end units most likely are not practical or
single sheet or an entire
cost effective for the average woodland owner.
book that lists log volumes for each log length
and scaling diameter
(Table 2, page 6). Tables are available in
Topographic map A map that shows
board-foot and cubic‑foot measures. OSU
terrain (ridges, draws, and flat areas) by
Extension publication EC 1127, Measuring contour lines. The contour lines indicate
Timber Products Harvested from Your
locations of equal elevation and make it
Woodland (see back page), also contains log possible to measure the slope of the ground
volume tables.
from the map. Widely
Pacing This is a
spaced contour lines
skill rather than a tool,
indicate flat or gentle
but it can be—and
ground; closely
commonly is—substispaced lines indicate
tuted for tools when
steep ground.
horizontal distance
Tarif access tables
measurements do not
Tables that list the
need to be precise
tarif number for
(Figure 8, page 4).
individual tree speThe best way to detercies, such as Douglasmine your pace is to
fir (Table 3, page 7)
count your steps as
based on total tree
you walk an accurately
height and diameter
measured distance
at breast height (dbh).
using the same kind
A low tarif number
of pace you use for
means the tree has
everyday walking.
much taper; a high
Rangefinder This
tarif number means
convenient optical
it has minimal taper.
device provides horiFor details, and more
zontal measurements
tarif access tables, see
that are more precise
OSU Extension publithan most pacing but
cation EC 1190, Stand
less precise than tapVolume and Growth:
ing. Rangefinders are
Getting the Numbers
Figure 6.—A core sample obtained from
particularly useful
(see back page).
a tree with the incremental borer enables
when a person works
the user to determine a tree’s growth rate.
alone.
FOREST MEASUREMENT 3
Tree volume tables Tables that
list the wood volume of individual
tree species in board-foot or cubicfoot volumes. Table 2, a sample, is
based on tarif number, log length,
and dbh for each tree. More tree
volume tables are in Stand Volume
and Growth: Getting the Numbers.
The Woodland Stick Any of
several sticks or other devices to
help you make simple and relatively accurate estimates of tree
height and diameter (Figure 7).
The Woodland Stick also has an
abbreviated log volume table for
determining Scribner log volumes
in standing trees.
Comparing tools
Figure 8.
—Pacing
can be a
fast, easy
way to
estimate
area and
horizontal
distances.
However,
pacing accuracy
can range
widely, with
results from
moderately
accurate to
very crude.
Practice in order to develop a consistent pace. You
might want to buy a pedometer, such as those sold
in sporting goods stores, to count your paces.
Use Table 1 to compare tools
that can be used for similar tasks.
First, check the key at the bottom.
The three numbers indicate the degree of
precision and the degree of difficulty in use.
Determine what you want to measure and
consider all the tools in the left column.
Some are quick and easy to use but yield
less precise results. Others are more difficult to use—and may or may not give more
precise results.
Select a tool that fits the objective. For
example, if you want to measure a road
grade, you can choose between a clinometer and a topographic map. The clinometer is rated at 2 for precision (that is,
moderately precise) and 2 for ease of use
(that is, moderately easy to use).
The topographic map is rated 1 for precision in measuring road grade (that is, less
precise than the clinometer), and it’s rated
2 for ease of use (moderately easy to use).
Considering both methods of measurement,
the clinometer would be the better option
because it has a better degree of precision
and is equally easy to use.
Tools discussed here are available from
many sources. Most are stocked in local
reforestation or logging supply stores;
others can be obtained from mail-order
suppliers. Tool and
supply catalogs
are available in
Extension offices
in many counties.
A new tool usually comes with
instructions, but
novices often need
help with certain
instruments. Ask
the forester in the
OSU Extension
office nearest you
for additional pubFigure 7.—The Woodland Stick is an easy-to-use
lications or sources
and moderately accurate tool for measuring tree
of assistance.
height and diameter. It must be held 25 inches
from the eye; at any other distance, it gives incorrect readings.
4 THE WOODLAND WORKBOOK
Table 1.—Rating precision and convenience of tools for various measuring tasks
Measurement tasks
Angle gauge
Clinometer
Compass
Global Positioning
System (GPS) 1
Increment borer
Logger’s tape 2
Log volume table
Pacing
Rangefinder
Tarif access tables 3
Topographic map
Woodland Stick
Precision
2
Ease of use
2
Precision
2
2
2
3
1
2
1
3
1
1
1
3
Ease of use
2
2
2
2
3
3
3
Precision
Ease of use
Precision
Ease of use
3
2
3
3
3
3
3
Ease of use
Precision
3
1
3
1
3
3
2
Precision
3
Ease of use
Precision
Ease of use
Precision
Ease of use
Height
2
Precision
Ease of use
Volume
2
2
Ease of use
Precision
Diameter
2
Precision
Ease of use
Current growth
2
Ease of use
Precision
Basal area
Age
Trees
Volume
Length
Diameter
Logs
Ground slope
Road grade
Horizontal distance
Horizontal angles
Tools
Area
Boundaries
2
1
2
1
2
2
2
3
3
1
3
2
3
Precision: 1= less precise; 2 = moderate; 3 = more precise
Ease of use: 1 = difficult to use; 2 = moderate; 3 = easy to use
1
Global Positioning Systems (GPS) come in a wide price range; price directly relates to accuracy.
2
Logger’s tape cartridge with feet and inches on one side and tree diameter (inches) on other side.
3
Tarif access tables include tarif tables for individual species and tree volume table.
FOREST MEASUREMENT 5
6 THE WOODLAND WORKBOOK
10
10
20
20
20
20
30
30
30
60
60
70
80
80
80
100
110
140
140
160
160
180
180
180
210
210
210
250
250
250
10
10
20
20
20
20
20
30
30
30
50
60
70
70
80
80
80
100
100
130
130
130
150
150
150
150
170
170
170
170
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
340
340
300
300
250
250
250
210
210
180
180
160
160
140
140
110
110
80
80
70
70
60
30
30
30
20
20
20
10
10
17
380
380
330
330
330
290
240
240
200
200
170
170
150
160
140
140
110
110
90
90
70
70
60
30
30
30
20
20
10
10
18
500
450
450
390
340
340
300
300
250
250
210
210
180
170
150
130
130
110
110
90
90
70
60
60
30
30
20
20
10
10
19
580
500
450
450
390
390
340
340
300
250
250
210
210
180
180
160
130
130
100
110
90
80
70
60
40
30
30
20
10
10
20
580
580
500
500
450
390
390
340
340
300
250
250
210
210
180
160
160
140
130
100
80
90
80
70
60
30
30
20
10
10
21
640
590
590
510
460
460
400
400
350
310
310
260
250
210
180
180
160
160
140
110
100
80
90
80
60
40
30
30
10
10
22
700
640
590
590
510
460
460
400
350
350
310
310
260
220
220
180
180
160
140
140
110
80
80
80
80
60
30
30
10
10
23
720
660
640
590
590
510
460
460
400
350
350
310
260
260
220
190
190
160
160
140
110
110
80
70
80
60
40
30
10
10
24
Condensed from VARPLOT Scribner Volume Tables.
1
16
15
7
820
730
670
670
620
530
530
480
420
400
350
310
310
260
220
220
190
190
160
140
140
110
80
80
80
70
40
30
30
10
25
850
770
770
690
640
640
550
500
490
420
370
370
310
260
260
220
190
190
170
150
140
110
110
80
70
70
60
30
30
10
26
900
820
800
740
710
660
580
560
510
440
440
390
330
330
260
220
220
190
170
170
150
110
110
90
70
70
70
40
30
10
27
920
820
820
740
660
640
590
510
500
420
380
360
310
260
260
220
170
170
150
120
110
90
80
60
70
30
30
31
980
860
820
770
660
660
590
530
510
460
380
380
310
310
260
220
220
170
150
120
120
90
80
70
60
40
30
32
920
920
820
700
700
620
560
540
480
420
420
340
280
270
230
210
180
150
120
100
90
80
60
40
30
35
910
830
780
670
610
560
510
450
450
380
300
300
250
220
210
180
130
120
100
80
70
40
30
38
920
920
780
730
680
610
510
490
450
380
380
300
250
230
210
180
150
120
100
90
70
40
30
39
990
940
840
740
690
620
530
510
450
380
380
310
270
230
220
190
150
120
100
90
70
40
30
40
870
820
750
640
580
550
500
400
380
340
280
260
230
200
150
150
100
90
70
60
30
42
900
820
770
690
590
550
510
430
400
340
280
280
230
200
160
150
110
90
70
70
30
43
950
850
770
710
600
590
510
440
430
340
280
280
240
200
200
150
110
90
80
70
30
44
970
910
860
710
670
600
520
440
430
370
310
280
240
220
200
150
130
90
80
70
30
45
1020 1020 1050 1120 1120
950 1020 1020 1050 1050
870
740
740
630
580
540
450
400
380
310
280
250
230
190
150
150
100
90
70
40
30
41
960 1010 1030 1070 1120 1140 1170 1170 1200
910
760
760
650
590
560
490
450
430
370
300
280
250
210
210
180
120
100
100
80
60
40
30
37
980 1010 1030 1150 1180 1200 1230 1290 1320 1340
940
840
740
700
650
560
560
490
420
420
340
300
280
230
210
200
180
120
100
100
80
60
40
30
36
980 1040 1060 1120 1140 1180 1260 1260 1290 1320 1320 1440
920
820
780
700
620
610
530
480
460
420
340
340
270
230
230
200
170
150
120
100
90
80
60
40
30
34
980 1020 1120 1190 1220 1250 1320 1340 1370 1450 1450 1510 1530
980
870
820
780
660
610
590
530
460
460
390
330
310
270
230
220
190
150
150
120
90
80
70
60
40
30
33
880 1000 1060 1100 1100 1180 1200 1280 1320 1340 1470 1480 1510 1550 1660 1720
880
790
740
740
640
590
560
500
420
420
360
360
300
260
240
190
170
170
150
120
110
90
70
60
70
30
20
30
960 1000 1050 1100 1160 1230 1240 1320 1340 1430 1450 1470 1510 1630 1650 1720 1730
850
850
780
710
710
610
560
530
470
400
400
350
300
290
240
190
190
170
150
150
110
90
90
70
60
40
30
20
29
920 1020 1060 1110 1160 1210 1230 1310 1450 1530 1560 1580 1700 1700 1740 1810 1880 1950
920
820
760
760
690
610
580
530
450
450
400
390
350
280
280
220
190
190
170
150
140
110
90
80
70
70
40
30
10
28
Tarif numbers
Table 2.—Tree volume table (Scribner volume table, 32' logs to 5" top).1
DBH (inches)
16
15
15
15
8
9
10
16
15
13
17
16
15
15
15
15
16
17
18
19
17
16
15
25
16
17
19
20
21
22
Height (feet)
95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170
25
25
25
25
26
26
26
27
27
27
28
28
29
29
30
31
31
32
33
34
34
36
37
38
40
42
26
27
27
27
28
28
28
28
29
29
30
31
31
31
32
32
33
34
34
36
36
38
39
40
41
27
27
27
28
28
28
28
29
29
30
30
30
31
31
32
32
33
34
34
35
36
37
38
39
40
41
43
28
28
29
29
29
30
30
30
31
31
32
32
32
33
33
34
35
36
36
38
38
39
40
41
42
43
29
30
30
30
31
31
31
32
32
33
33
34
34
35
35
36
36
38
38
39
39
40
41
42
31
31
32
32
32
33
33
33
34
35
35
35
36
36
37
38
38
39
40
41
41
42
43
33
33
33
33
34
34
34
35
35
36
36
37
38
38
38
39
40
41
41
42
43
34
34
34
35
35
35
36
37
37
38
38
38
39
40
40
41
42
42
43
35
35
36
36
37
37
38
38
38
39
39
40
41
41
42
43
43
37
37
38
38
38
38
39
39
40
41
41
42
42
43
43
38
38
39
39
39
40
40
41
41
42
43
43
44
39
40
40
40
41
41
42
42
43
43
41
41
41
42
42
43
43
44
42
43
43
43
44
44
44
45
45
44
45
45
44
45
45
44
45
44
45
45
44
45
44
45
44
45
44
45
44
45
45
44
45
45
45
44
44
90
25
23
23
23
24
24
24
25
25
25
26
26
27
27
27
28
28
29
29
30
31
32
32
34
35
36
38
39
42
85
26
21
21
22
22
22
23
23
23
23
24
24
25
25
25
27
27
27
28
28
29
30
30
31
32
34
36
38
40
80
24
15
35
20
20
21
21
21
21
21
22
22
22
23
23
23
24
24
25
25
27
27
27
28
29
29
30
31
33
35
37
75
36
15 17 18 19 21 22 24
1
Condensed from VARPLOT Tree Volume Tarif Access Tables (2002).
19
19
19
19
19
19
20
21
21
21
21
21
21
22
22
23
23
24
24
25
25
27
27
28
29
30
32
33
70
26
17
17
17
17
18
18
18
19
19
19
19
19
19
21
21
21
21
22
23
23
24
24
25
27
27
28
30
31
65
24
16
16
16
15
15
32
33
16
16
16
17
17
17
17
17
18
18
18
18
19
19
21
21
21
21
22
23
24
25
25
27
29
60
34
15
15
15
29
31
15
28
30
15
15
26
27
16
15
15
16
23
15
22
17
17
17
18
18
18
19
19
21
21
21
22
24
25
26
55
24
15
15
20
21
16
16
17
15
15
14
18
18
19
21
21
22
23
50
15
16
15
15
11
17
18
19
20
45
12
17
17
15
7
40
35
30
Table 3.—Tarif access table for Douglas-fir.1
DBH (inches)
FOREST MEASUREMENT 7
For more information
Bowers, S., N. Coleman, and R.A. Fletcher.
2004. Stand Volume and Growth:
Getting the Numbers, EC 1190.
Bowers, S. and N. Coleman. 2007. Tarif
Access Tables: A Comprehensive List,
EC 1609.
Holmberg, J. 2006. Land Measurement and
Survey, PNW 581.
Oester, P. and S. Bowers. 2003. Measuring
Timber Products Harvested from Your
Woodland, EC 1127.
These publications and many others can
be viewed, downloaded, and ordered from
the OSU Extension website at
http://extension.oregonstate.edu/catalog/
Click on “Forestry and Wood Products.”
Or, order printed copies from:
Publication Orders
Extension & Station Communications
Oregon State University
422 Kerr Administration
Corvallis, OR 97331-2119
Fax: 541-737-0817
e-mail [email protected]
Please check current pricing and availability before you order. Shipping and
handling charges are in addition to publication charges.
We offer a 25-percent discount on orders
of 100 or more copies of a single title.
© 2004 Oregon State University
The Woodland Workbook is a series of some 60 publications prepared by Oregon State University Extension foresters
specifically for owners and managers of private, nonindustrial woodlands. Workbook publications contain information of
long-range and day-to-day value for anyone interested in wise management, conservation, and use of woodland properties.
Publications are available for purchase separately. For information about how to order, and for a current list of titles and
prices, contact the OSU Extension Service office that serves your county. Or, visit the Extension website at
http://extension.oregonstate.edu/catalog/ Click on “Forestry and Wood Products.”
Extension work is a cooperative program of Oregon State University, the U.S. Department of Agriculture, and Oregon
counties. Oregon State University Extension Service offers educational programs, activities, and materials—without
regard to race, color, religion, sex, sexual orientation, national origin, age, marital status, disability, and disabled veteran
or Vietnam-era veteran status—as required by Title VI of the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, and Section 504 of the Rehabilitation Act of 1973. Oregon State University Extension Service is an Equal
Opportunity Employer.
Revised April 2004. Reprinted September 2008.