Case Studies Forestry and Urban Tree management projects

Forestry Tasmania

Usage of full waveform Lidar in forestry taxation

Objective of the Project:

Forestry Tasmania is Australia’s biggest forestry operator and handles approximately 3.5 Mio ha of plantations and native forests. In 2008 Forestry Tasmania contracted Dimap to fly a test area of 6000 ha with the full waveform Lidar to develop optimized taxation procedure of the forests using Lidar technology to reduce the taxation costs and get full area taxations with faster turnaround times of the data.

The solution should also provide additional data layer for other departments like harvesting planning.

Technical Solution:

Dimap applied the Riegl 560 full waveform scanner together with a digital camera to fly the steep mountain terrain in central Tasmania generating more than 4 pts/sqm and an Orthophoto with a resolution of 10cm while forestry Tasmania collected traditional plot data for the different forest structures. During the processing Dimap provided not only the Images, intensity images, LAS point files, DTM and DSM but also full waveform data and statistically summarized waveform data describing the forest in more details.

The ground plot data were then used to calibrate the Lidar data (using synthetic and real waveform data) and calculate top and mean heights, basal area per hectar and stem volumes with better than 90% accuracies. Furthermore the segmentation of the forests and additional data layer for the GIS system run by Forestry Tasmania were calculated. The stratification of the forests could be analysed as well as fuel load as part of the forest fire prevention.

Achievements:

The technology allowed Forestry Tasmania to reduce the manual field effort for taxations by 80% and ended in a setup to collect taxation data’s for the 3.5 Mio ha based on airborne full waveform Lidar within a 3 year project. The technology replaced the classical ground based taxation approach completely and is established as standard operation procedure.

During the project Dimap also found the tallest tree Australia’s with over 100m height.

Figure 1: LiDAR-derived metrics used to predict merchantable volume. Volume surfaces (merch vol/hectare) – high spatial precision.

Figure 2: Two views of the same patch – the stratified random sampling approach, and the LiDAR surface-based approach. LiDAR-based timber inventory has resolution at Strategic, Tactical and Operational levels.

Figure 3: LiDAR volume model predictions vs stratified random sampling derived estimates (plot predicted vs. measured) for native forest development model. Red line is the bias trend.

General comparison with classical photogrammetry approach:

Analysing publications from Canada, Australia and Scandinavia and comparing Dimap’s and other Lidar provider results with classical photogrammetry procedure results and ground plots following RMSE can be achieved. One has to note that the errors in forestry taxation using Lidar data are depending on the tree species (better RMSE for coniferous and plantations) and that individual tree detections works not on all species and only in the upper strata.

One has also to note that the integration of Hyperspectral tree species detection improves the results of the individual tree detection but also allows the collection of taxation parameters in mixed forest including the implementation of species dependent BHD-Height-Canopy diameter relationships.

Parameter Lidar based on forest stands Lidar based on individual tree detection min 8pts/sqm Lidar 4 pts/sqm and Hyperspectral approach Classical photogrammetry approach
Individual tree detection top strata N/A 15-25% 2-15% 0-5%
Individual tree detection second and third strata N/A 40-50% 30-40% Not possible
Number of trees per ha (also species dependent) 10-15% 5-20% 5-10% 20-30%
Species detection Possible in plantations based on intensity Not possible Non rainforests 5-30% Limited possible
Tree species distribution Not possible Limited possible 100% 20-30%
Mean tree height – absolute 40-60cm 20-40cm 20-50cm 30-70cm
Mean tree height – relative 5-10% 5-10% 5-10% 10-25%
Automatic Canopy diameter top strata N/A 20-50% 10-35% 10-40%
Basal area 10-15% 5-15% only plantations 5-25% Also mixed forest 20-30%
Mean diameter (depending on species) 10-15% 10-15% 10-15% 10-35%
Diameter distribution Not 10-20% 5-20% Not possible
Forestry relevant Volume per ha (tree species) 5-15% 5-20% 5-20% 15-30%
Carbon volume including branches 15-30% 10-20% 7-15% 20-40%

© DIMAP 2014

 

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