Adam Dick M.Sc.F. Candidate, University of New Brunswick 2007 Western Mensurationists Meeting June 24-26, 2007 Kelowna, B.C

Adam DickM.Sc.F. Candidate, University of New Brunswick2007 Western Mensurationists MeetingJune 24-26, 2007 Kelowna, B.C.

A Google example:

April 22, 2023 Adam Dick ~ Western Mensurationists Meeting 2






Photography has been an important tool used by foresters for many years

Satellite/ aerial photography underpins most large scale inventories

What if we could have an in-stand perspective to help interpret collected data?

Assist by making data collection more efficient?



Equipment Digital camera Tripod Tripod mount

Ensures nodal point of lens is above rotational axis of tripod

Eliminates parallax errors


Camera mounted vertically

Photo every 15-degrees

24 photos per plot Ensures adequate

overlap between adjacent images

Focus, flash settings the same around plot



Software (Panorama Factory v4.5) Automates stitching process Automatically corrects barrel distortion,

detects focal length


Unwrap and print out flat stand Distortion free Consistent scale


So………How can we use these photographs?


Using photography


To calculate distance to object Dimension of the tree

(or surrogate) And camera focal

length


i

DR f

a

Calculate azimuth to object


o3600.03 degrees/pixel

12,976

Azimuth of first tree measured used as reference

Could arbitrarily start at zero if only relative position of trees is required


Azimuth=7+(1515.59-227.05) 0.03

Using photography


Bitterlich 1948 “basal area density of a unit area of area can be

estimated by counting those trees whose diameter at breast height (dbh) subtended angles appearing larger than the horizontal angle-gauge” (Grosenbaugh 1958)


G zk

D ak

R b

Using a camera Decourt, N. 1956 Utilisation de la photographie

pour mesurer les surfaces terriers. Revue forestière française, Vol 8. No.7 pp.505-507

Adaptation of Bitterlich to use photographs


i

G zk

D a ak

R b f

Several methods identified to do ACS

Measure width of trees in photograph Calculate the BAF of

each tree Apply desired BAF

constant (e.g. mBAF2)


22 250 50 50 iD a a

BAFR b f

Calibrate gauge width for photograph

Count trees larger than gauge width


min50

i BAF fa

Do as a prism does Shift the tree at

breast height by gauge width

Tree overlaps: in Tree cut: out



49 plots Sampled trees with a mBAF1 prism 1400 trees sampled▪ Measured tree DBH▪ Distance and azimuth to each tree▪ Took photographs at each plot



Sampled across range of densities Stand types 2 camera models

Olympus D550Z, 3 megapixels Canon PowerShot SD200, 3.2 megapixels

Stand Density Class (stems/ha)

0 500 1000 1500 2000 2500 3000

Num

ber o

f Plo

ts

0

5

10

15

20

25

30

Azimuth calculations Linear regression

Field measurements vs. measurements from photo



Distance calculations Linear regression

Field measurements vs. measurements from photo

Photography is underestimating the distance

Azimuth is generally good

Relative positions of the trees is good

Need to adjust the focal length


TREE VISIBILITY BY BAF SELECTION

Tree Visibility by BAF selection

mBAF Factor1 2 3 4 5 6

Perc

ent V

isib

le %

0

20

40

60

80

100

120

TREE VISIBILITY BY DISTANCE

Tree Visibility by Distance

Distance from plot centre (m)0 5 10 15 20 25 30 35

Num

ber o

f Tre

es

0

20

40

60

80

100

120

140

160

180

% o

f Tre

es V

isib

le

0

20

40

60

80

100

120

140

160

180

# of trees measured# of trees visiblepercent of tres visible



BAF calculations Field measurements

vs. measurements from photo


Other Applications As a monitoring tool Repeated measures


Plot 52 – Pre Harvest

Plot 52 – Post Harvest

Maintain data integrity Prescription training

tool

Documents

Adam Dick M.Sc.F. Candidate, University of New Brunswick 2007 Western Mensurationists Meeting June 24-26, 2007 Kelowna, B.C