the application of digital photogrammetry techniques for

Techniques for recordingThe Application of Digital Photogrammetry and Crown Delineation Techniques to derive and

Monitor Tree and Stand Characteristics

David Miller1, Georgios Zagaligis2 and Andrew Cameron2

1 Macaulay Institute2 University of Aberdeen

Techniques for recordingAcknowledgements

The Scottish Executive Environment and Rural Affairs Department

The Forestry Commission Scotland

Ordnance Survey

CRWorld Ltd

GetMapping Ltd.

David Miller, Macaulay Institute

Techniques for recordingObjectives

• Test the derivation of tree stand characteristics compared with ground survey techniques

• Assess changes in stand characteristics through time


Techniques for recordingKey Forest Stand Parameters

Species Sitka spruce

Development stage Cut, young and mature

Net Volume and Mean Volume of timber per unit area Tree Volume

Canopy Height Mean tree height by species

Comparisons made using plot and tariff surveys and derived from aerial imageryDavid Miller, Macaulay Institute

Techniques for recordingExtracting Tree Canopy Data: Aerial Imagery

Dbh

Crown projection area

Crown width

Total tree height

b

• Stereo aerial imagery• DEM derivation • Stand volume estimation

DEM Orthophotograph

Techniques for recordingStudy Sites

Land Cover of Great Britain, 1990, ITE

Three study areas: North east Scotland

Undulating terrain

North west ScotlandMountainous terrain

Mid-WalesPlateau and multi-date

Issues of terrain, sun illumination and stand age

Techniques for recordingField Survey and Tariff

20 m

New cut forest edge: tree height observations

Example for North east Scotland – Rosarie Forest

Techniques for recordingDigital Ortho-image Processingfor Crown Delineation

Extraction of coordinates of each tree visible within the stand

Extraction of crown dimensions: area, diameter

Digital orthoimage

Logarithmic equalisation filter 15 x 15

Low-pass filter

Masking out non-forested areas


Techniques for recordingAutomated Canopy Delineation

b

Distance (m)

Distance (m)

Height (m)

Ground surface

Tree canopy

Delineated crown

Omission error

Commission error

• Analysis of orthophoto and DEM to identify and delimit tree canopies


Issue of definition of individual or clusters of trees

Techniques for recordingEstimation of Tree Diameter

Crown area or crown diameter Estimated tree height

Regression analysis

Dbh estimation

Issues of impact of estimates of tree height and numbers


Techniques for recordingTree dbh vs. Delineated Tree Crown Area

0.00.51.01.52.02.53.03.54.04.55.0

10 20 30 40 50 60

Tree dbh (cm)

Crow

n ar

ea (m

2 )

Pearson Correlation

r = 0.792 *

* correlation is significant at the 0.01 probability level.

Techniques for recordingComparison of Forest Stand Parameters Between Field Surveys and Derived Values

Random plot survey Abbreviated tariff Derived from

aerial dataTrees/ha 1600 1479 1145

Mean height (m) - 21.4 22.0

Top height (m) 25.1 - 22.8

Mean dbh (cm) 25 23 27.6

Mean vol/tree (m3) 0.5 0.5 0.6

Basal area/ha (m2/ha) 79.8 66.6 72.2

Net vol./ha (m3/ha) 839 704 689.5704 689.5

25.1 22.8


Techniques for recordingCwm Berwyn: Mid-Wales

Multiple dates of imageryUpland plateau

Techniques for recordingCanopy Surface Compared with Canopy Type

Canopy type No. of Points Field obs Model obs. Difference Standard Deviation p-Value(mean height, m) 1995 mean field - mean model

Uniform 26 15.1 14 1.1 2.1 0.16Partially disrupted 105 14.6 14.2 0.4 2 0.36Disrupted 6 13 12.6 0.6 1.4 0.84Gap 7 15.3 11.2 4.1 1.9 0.02Thinned 14 17.5 15.9 1.6 2.2 0.19

Poorest quality of derivation in areas of canopy gaps and uneven surfaces


Techniques for recordingCanopy Surface

A

B

DEM: 1995

A B

300

470 Transect through canopy: 1995

Distance (m)

A

B

Orthophotograph: 1995

Techniques for recordingMultiple Dates of Coverage

1957 1975

1992 1995

• Orthophotographgenerated for each date

Techniques for recordingMultiple Derived Surfaces

1992 1995• DEM generated

for each date of imagery

• Derivation of canopy outlines for each date

Techniques for recordingChanges in Forest Stands

• Perspective views of forest at different dates

1957 1975

• Changes in forest

1992 1995stands

Techniques for recordingChange: 1995 -2000

1995/2000

Felling

2000

Techniques for recordingComparison of Forest Stand Parameters For Multiple Dates and Field Survey

Forest Survey, 2000

1992, from aerial data

1995, from aerial data

Trees/ha 1400 1182 1219

Mean height (m) 22.3 20.1 21.3

Top height (m) 25.1 22.1 22.8Mean dbh (cm) - 25.9 26.2

Mean vol/tree (m3) 0.53 0.58 0.59

Net vol./ha (m3/ha) 740 704 689.5685.9 715.1


Techniques for recordingPotential Limitations

• Canopy delimitation: errors in commission, but mainly omission

• Shape of crown and dominance class of each tree• Horizontal resolution and accuracy of DEM, DTM

and ortho-photographs• Viewing geometry, sun elevation, illumination of the

crown, filter size and type used• Accuracy of the derived coordinates of tree apex


Techniques for recordingCurrent Activity

• Test results against data gathered post-felling

• Compare different models for deriving dbh for multi-date imagery

• Assess the sensitivity of tree apex calculations to multiple dates of imagery


Techniques for recordingFuture Potential

• Value-added inventory • Geo-referencing of individual/clusters of trees• Improved estimates of Net volume/ha• Join-up inventory, forecasting with individual ‘tree

history’• Potential for targeting of

updates to yield estimates using information triggered by management plans

Techniques for recordingCompartment Comparison: Two Study Sites

Stand parameters/Statistics Mean Standard deviation Range

dbh (cm) 23 6.8 9 - 41

Height (m) 21.5 3.8 12.0 – 27.0

Leanachan Forest: North-west Scotland

Stand parameters/Statistics Mean Standard deviation Range

dbh (cm) 29.9 5.8 18 – 43

Height (m) 24.3 1.6 19.8 – 26.6

Rosarie Forest: North-east ScotlandStand. Dev. of height < Stand. Dev. Of DBH


the application of digital photogrammetry techniques for

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