72 LIDAR Derived Forest Metrics - Calvert Island - 20 Meter Spatial Resolution

LIDAR forest metrics have been developed for the Calvert Island region. The data are in 20 meter resolution and detail a number of variables about the vegetation layer above the bare earth model. Forest metrics have been grouped to show major statistical themes such as gap fraction, stem height, and density. The information is valuable for classifying forest structure and better understanding ecosystem dynamics.

LIDAR Forest Metrics Produced by GWF LiDAR Analytics
A full list of derived forest metrics produced by G.W. Frazer is listed at the end of this abstract.

LIDAR flights conducted in 2012 and 2014 covered all of Calvert and Hecate Island. Flights were completed in August of 2012 (Terra Remote Sensing) and August of 2014 (Brian Menounos UNBC).

Area-based canopy height and density metrics are derived directly from a height-normalized LAS point cloud using proprietary software developed by G.W. Frazer (note: Fusion and LASTools are respectively open-source and commercial software that can be used to extract various area-based canopy metrics). These gridded products (approximately 55 bands) have a user-defined 20 m spatial resolution and include (i) height-based statistics (e.g., min., max., mean, moments, percentiles), (ii) density-based statistics (i.e., gap fraction, canopy cover at fractional and absolute heights above the ground surface), and (iii) diagnostic information (e.g., number of laser points in each cell, number of laser points classified as ground, number of points above a specific height threshold, etc.). Area-based canopy metrics are used to characterize the three-dimensional (3-D) structure of the vegetation canopies.

Summary LiDAR acquisition metadata:
2012 Terra Remote Sensing

On August 5th, 15th,and 17th, 2012, TRSI collected hyperspectral, lidar and digital image data in four project sites at and near Calvert Island, B.C. using a fixed wing aircraft with lidar system and hyperspectral sensor. A combined GPS/INS System (Inertial Navigation System) is used for aircraft attitude and position. A total of 477.22 km2 was covered on this mission. Flight height was 1150 metres AGL to retain 1.5 metre spatial resolution for hyperspectral Imagery. Calibration flights were conducted at the airport in Port Hardy, BC Canada. These flights were performed immediately after the completion of the project acquisition and consisted of two opposing flight lines along the runway and two perpendicular flight lines in relation to the runway. This pattern allows us to calibrate our system and solve for roll, pitch, and heading. The conditions required to complete the survey as originally intended to meet higher accuracy specifications never presented. Weather and local fog prevented the use of local airports and as such our flight baseline length were longer than anticipated; further, we were unable to position project control within the survey area. Due to these factors, the vertical accuracy of the survey should be considered at +/- 20cm relative and 1m absolute when compared against hard flat surfaces.
Site Size: 477.22 km2
Projection: UTM Zone 9
Datum: NAD 83
Geoid: HT 2.0
Accuracy:
Lidar Points: a relative accuracy of +/-15 cm and absolute accuracy of 1m Hyperspectral Data: +/- 2 pixel
Point Cloud Density: Taking random samples throughout the project area, the average point density for a single flight line is 1pts/m2
Due to the fact that the majority of the area is covered by overlapping flightlines, the point density averages closer to 2 pts/m2

2014 UNBC LiDAR Research Group:
Flight - Aug. 7, 2014 - Flight was designed to cover four large gap areas in the 2012 LiDAR as well and enhance NW Calvert Island LiDAR results.
Scanner Type: Riegl VQ-580
Point density ranged from 22.3 pts/m2 to 3.4 pts/m2
Lidar points were processed in CSRS NAD83 UTM Zone 9, but use ELLIPSOID heights. Conversion
to CGVD28 was completed after DEM creation using GPS-H.
Supervisor: Brian Menounos
Technician: Rob Vogt
A GPS base station established by Hakai's Keith Holmes at Pruth Bay was used to position Lidar data (see page 5 for details regarding the base station).
Precise trajectory for the plane is solved using PosPac MMS. A calibration line across the base station both before and after the survey was used to aid in forward and reverse processing of the trajectory.
Precise location for the base station was adjusted using NR Can's PPP. Position accuracy of the trajectory is ±3 cm.

For a full metadata report on LiDAR acquisition please contact data@hakai.org

List of LiDAR-Derived Canopy Height, Canopy Density, and Stem Metrics:
(Based on G.W. Frazer LiDAR Metrics for Calvert / Hecate Island Acquisition 2012 / 2014 metadata document.)

Table 1: Canopy Height Metrics (filename prefix: *hgt*)

Band - Name - Description
1 - AMH - Arithmetic mean height (m) of laser points ≥ min. height threshold
2 - QMH - Quadratic mean height (m) of laser points ≥ min. height threshold
3 - CMH - Cubic mean height (m) of laser points ≥ min. height threshold
4 - STDEV - Standard deviation of heights (m) of laser points ≥ min. height threshold
5 - AAD - Absolute average deviation of heights (m) of laser points ≥ min. height threshold
6 - LCOV - Coefficient of variation (2nd L-moment about the mean)
7 - LSKEW - Coefficient of skewness (3rd L-moment about the mean)
8 - LKURT - Coefficient of kurtosis (4th L-moment about the mean)
9 - PCOV - Coefficient of variation (2nd central moment about the mean)
10 - PSKEW - Coefficient of skewness (3rd central moment about the mean)
11 - PKURT - Coefficient of kurtosis (4th central moment about the mean)

Table 2: Canopy Density Metrics (filename prefix: *dens*)

Band - Name - Description

1 - GAP - Gap fraction = ratio of number of laser points 5 and 10 m above ground surface

4 - CD3 - Percentage of laser points found between >10 and 20 m above ground surface

5 - CD4 - Percentage of laser points found between >20 and 30 m above ground surface

6 - CD5 - Percentage of laser points found between >30 and 40 m above ground surface

7 - CD6 - Percentage of laser points found between >40 m and max. height threshold (90m) above ground surface

Table 3: Percentiles of Laser Canopy Height (LHQ) Bands (filename prefix: *lhq*)

Band - Name - Description
1 - LHMin - Minimum laser canopy height (q = 0.00)
2 - LH05 - 5th Percentile of laser canopy height (q = 0.05)
3 - LH10 - 10th Percentile of laser canopy height (q = 0.10)
4 - LH15 - 15th Percentile of laser canopy height (q = 0.15)
5 - LH20 - 20th Percentile of laser canopy height (q = 0.20)
6 - LH25 - 25th Percentile of laser canopy height (q = 0.25)
7 - LH30 - 30th Percentile of laser canopy height (q = 0.30)
8 - LH35 - 35th Percentile of laser canopy height (q = 0.35)
9 - LH40 - 40th Percentile of laser canopy height (q = 0.40)
10 - LH45 - 45th Percentile of laser canopy height (q = 0.45)
11 - LH50 - 50th Percentile (median) of laser canopy height (q = 0.50)
12 - LH55 - 55th Percentile of laser canopy height (q = 0.55)
13 - LH60 - 60th Percentile of laser canopy height (q = 0.60)
14 - LH65 - 65th Percentile of laser canopy height (q = 0.65)
15 - LH70 - 70th Percentile of laser canopy height (q = 0.70)
16 - LH75 - 75th Percentile of laser canopy height (q = 0.75)
17 - LH80 - 80th Percentile of laser canopy height (q = 0.80)
18 - LH85 - 85th Percentile of laser canopy height (q = 0.85)
19 - LH90 - 90th Percentile of laser canopy height (q = 0.90)
20 - LH95 - 95th Percentile of laser canopy height (q = 0.95)
21 - LHMax - Maximum laser canopy height (q = 1.00)

Table 4: Canopy Density at Fractional Canopy Heights (CCF) Bands (filename prefix: *ccf*)

points (N_TOTAL) within grid cell

Band - Name - Description
1 - CC00 - Ratio of laser points ≥ min. height threshold (f = 0.00) to total number of laser points(N_TOTAL) within grid cell (note: CC00 = 1 – GAP FRACTION)
2 - CC05 - Ratio of laser points ≥ fractional height threshold (f = 0.05) to total number of laser points (N_TOTAL) within grid cell
3 - CC10 - Ratio of laser points ≥ fractional height threshold (f = 0.10) to total number of laser points (N_TOTAL) within grid cell
4 - CC15 - Ratio of laser points ≥ fractional height threshold (f = 0.15) to total number of laser points (N_TOTAL) within grid cell
5 - CC20 - Ratio of laser points ≥ fractional height threshold (f = 0.20) to total number of laser points (N_TOTAL) within grid cell
6 - CC25 - Ratio of laser points ≥ fractional height threshold (f = 0.25) to total number of laser points (N_TOTAL) within grid cell
7 - CC30 - Ratio of laser points ≥ fractional height threshold (f = 0.30) to total number of laser points (N_TOTAL) within grid cell
8 - CC35 - Ratio of laser points ≥ fractional height threshold (f = 0.35) to total number of laser points (N_TOTAL) within grid cell
9 - CC40 - Ratio of laser points ≥ fractional height threshold (f = 0.40) to total number of laser points (N_TOTAL) within grid cell
10 - CC45 - Ratio of laser points ≥ fractional height threshold (f = 0.45) to total number of laser points (N_TOTAL) within grid cell
11 - CC50 - Ratio of laser points ≥ fractional height threshold (f = 0.50) to total number of laser points (N_TOTAL) within grid cell
12 - CC55 - Ratio of laser points ≥ fractional height threshold (f = 0.55) to total number of laser points (N_TOTAL) within grid cell
13 - CC60 - Ratio of laser points ≥ fractional height threshold (f = 0.60) to total number of laser points (N_TOTAL) within grid cell
14 - CC65 - Ratio of laser points ≥ fractional height threshold (f = 0.65) to total number of laser
15 - CC70 - Ratio of laser points ≥ fractional height threshold (f = 0.70) to total number of laser points (N_TOTAL) within grid cell

16 - CC75 - Ratio of laser points ≥ fractional height threshold (f = 0.75) to total number of laser points (N_TOTAL) within grid cell

17 - CC80 - Ratio of laser points ≥ fractional height threshold (f = 0.80) to total number of laser points (N_TOTAL) within grid cell

18 - CC85 - Ratio of laser points ≥ fractional height threshold (f = 0.85) to total number of laser points (N_TOTAL) within grid cell

19 - CC90 - Ratio of laser points ≥ fractional height threshold (f = 0.90) to total number of laser points (N_TOTAL) within grid cell

20 - CC95 - Ratio of laser points ≥ fractional height threshold (f = 0.95) to total number of laser points (N_TOTAL) within grid cell

21 - CC100 - Ratio of laser points ≥ fractional height threshold (f = 1) to total number of laser points (N_TOTAL) within grid cell

Table 5: Diagnostic Bands (filename suffix: *diag*)

Band - Name - Description
1 - N_Total - Total number of laser points within grid cell
2 - N_Above - Total number of laser points ≥ minimum height threshold1
3 - N_Below - Total number of laser points maximum height threshold2
5 - N_Class - Total number of laser points classified as ground points

Table 6: Tree-Top Bands (filename suffix: *stm_hgt*)

Band - Name - Description
1 - N_Stem - Number of stems in grid cell
2 - SPH - Number of stems per hectare
3 - AMH_Stem - Arithmetic Mean stem height
4 - QMH_Stem - Quadratic mean stem height
5 - Min_Stem - Minimum stem height
6 - Max_Stem - Maximum stem height
7 - STDEV_Stem - Standard deviation of mean stem height