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Steve Reutebuch Hans-Erik Andersen Bob McGaughey Demetrios Gatziolis

Use of airborne laser scanning (LIDAR) as a tool for forest measurement and monitoring: use and potential. Steve Reutebuch Hans-Erik Andersen Bob McGaughey Demetrios Gatziolis Resource Monitoring & Assessment Program Vegetation Monitoring & Remote Sensing Team USDA Forest Service

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Steve Reutebuch Hans-Erik Andersen Bob McGaughey Demetrios Gatziolis

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  1. Use of airborne laser scanning (LIDAR) as a tool for forest measurement and monitoring: use and potential Steve Reutebuch Hans-Erik Andersen Bob McGaugheyDemetriosGatziolis Resource Monitoring & Assessment Program Vegetation Monitoring & Remote Sensing Team USDA Forest Service PNW Research Station

  2. LIDAR—what is it? • Light detection and ranging (LIDAR) • Uses laser light to measure distance • Different detection approaches • Time of flight • Phase difference • Hundreds of applications • In natural resources, 3 LIDAR types are widely available

  3. Widely available LIDAR • Terrestrial laser scanning (TLS) • Primarily used in engineering • Some use in forestry research scanning plots or individual trees and logs

  4. Widely available LIDAR • NASA IceSAT satellite LIDAR • Global- and continental-scale forest canopy height and biomass estimates • 70 m diameter footprint • 175 meters spacing • Difficult to remove topographic effects on canopy heights • Operational 2003-2009 • IceSAT-2 launch 2016 ???

  5. Widely available LIDAR • Airborne laser scanning (ALS) • Routinely flown commercially over large areas • Large vendor pool • Mature mission specs & deliverables • Mature software to process data • Many state and federal partners

  6. ALS LIDAR data uses • Topographic mapping of bare earth surface—primary use • Engineering • Flood risk mapping • Hydrologic modeling • Geologic mapping • Landslide mapping • Infrastructure mapping—still developing • Vegetation measurement and mapping—still developing, with operational uses

  7. National review of ALS LIDAR data needs • USGS National Digital Elevation Program: • Enhanced Elevation Data Requirements Study • Funded: USGS, FEMA, NRCS, NGA (DOD) • FY10-12: Conduct study • FY13: Initiate enhanced elevation data collection • Primary use: update bare earth surface models • USGS study recognizes many other uses • 130,000 sq miles of data with ARRA funds

  8. USGS recognized uses of LIDAR

  9. 2010 State LIDAR efforts • 8 states have statewide LIDAR programs • North Carolina, Louisiana, New Jersey, Maryland, Delaware, Pennsylvania, Ohio, Iowa • 8 states have program initiatives • Florida, Texas, New York, Oregon, Washington, Minnesota, South Carolina, Mississippi • Many more projects areas have been flown • ~25% of the conterminous US already has LIDAR collected • Unknown amount of private forest coverage

  10. 2010 Oregon LIDAR Consortium

  11. 2010 Puget Sound LIDAR Consortium

  12. Not all LIDAR data are the same • Things that affect LIDAR data for forest measurements: • Mission specs (pulse rate, scan pattern, flying height, airspeed, pulse diameter, etc.) • Time of year (leaf-off, leaf-on, snow free, etc.) • LIDAR sensor and data processing • Experience of LIDAR vendor

  13. Not all LIDAR data are the same Therefore, don’t expect to get same results when models from one LIDAR dataset are applied to other datasets, even in the same forest type!!!

  14. LIDAR used in forest measurement • When only partial LIDAR coverage of an area is possible: • Sampling within a multi-stage framework • Statistical framework has been developed and tested by several researchers • PNW LIDAR trials in Alaska: • Hans Andersen, PI • Kenai Peninsula • Interior Alaska

  15. Example: Multi-level sampling to support forest inventory in remote northern regions Wall-to-wall low- resolution coverage w/ LANDSAT TM, SPOT, etc. Subsampling high res. satellite imagery Remote sensing Subsampling with high res. LIDAR, aerial photos Measurements of trees, shrubs, moss, soils, down wood. Field plots

  16. PNW-RMA (Anchorage) is carrying out a project to test a multi-level approach for biomass estimation in the Tok (1,911 sq km) Multi-level approach will use: • Satellite imagery (Landsat, SPOT, PALSAR, Quickbird) • 27 High-density LIDAR strip samples • Field plot data (80 plots)

  17. LIDAR used in forest measurement • When “wall-to-wall” LIDAR coverage is available 2 types of measurements can be made: • Forest layers computed solely from the LIDAR • Inventory layers predicted from regression models or imputation methods using LIDAR and well measured ground plots

  18. 1– Layers computed solely from the LIDAR point cloud—obvious ones • Canopy surface model • Bare earth model

  19. 3-ft canopy surface model 3-ft bare earth model 1:12,000 aerial photo

  20. Layers computed solely from the LIDAR point cloud—obvious ones • Bare earth model • Canopy surface model • Canopy height model (Canopy surface minus ground surface)

  21. 3-ft resolution canopy height model Buildings

  22. Layers computed solely from the LIDAR point cloud—obvious ones • Bare earth model • Canopy surface model • Canopy height model • Canopy cover model

  23. % Canopy Cover (0.1 acre pixels)

  24. Layers computed solely from the LIDAR point cloud—obvious ones • Bare earth model • Canopy surface model • Canopy height model • Canopy cover model • Intensity image from 1st returns

  25. 1.5-ft resolution intensity image

  26. Layers computed solely from the LIDAR point cloud—not so obvious • Variance, standard deviation, skewness, kurtosis, etc. of the canopy • Mean, min, max, percentile heights of the canopy • Density of the canopy • Forest / non-forest mask

  27. Standard Deviation of Canopy Height

  28. LIDAR used in forest measurement • When “wall-to-wall” coverage is available 2 types of measurements can be made: • Forest layers computed solely from the LIDAR • Inventory layers predicted from regression models or imputation methods using LIDAR and well measured ground plots

  29. WARNINGS !!! • Can’t get species information from the LIDAR data • In some cases, can get: • Deciduous vs non-deciduous • Live crowns vs dead crowns • Can’t get understory, down wood, etc. • Not all LIDAR is the same: • Changes in LIDAR sensors, sensor settings, and flight parameters can change results

  30. MORE WARNINGS !!!!! • Most difficult part of a LIDAR project is: Getting good ground plot data: • Matched with regards to geographic position to an accuracy ~ equal to the LIDAR horizontal accuracy (~+/- 1m) • Matched with regard to the primary element being measured—large enough to minimize plot edge effect, but small enough to characterize tree size differences within plots (~0.1 – 0.2 ac circular plot)

  31. MORE WARNINGS !!!!! (cont.) • Most difficult part of a LIDAR project is: Getting good ground plot data: • Matched in time of measurement--generally within 1-2 yrs of LIDAR acquisition • Matched in what’s measured by the LIDAR and on the plot—all stems that make up a significant portion of the above ground canopy—generally down to a 7-10 cm DBH lower limit, including all species

  32. Examples of layers predicted from regression models • Sherman Pass Scenic Byway • Colville National Forest • 100,000 acres flown in 2008 • 74 1/10th acre plots used to develop LIDAR inventory regressions measured in 2008

  33. Sherman Pass LIDAR Project Forest cover minimum: 10ft ht & 2% cover in 66ft pixel Ground Plots

  34. Regression modelsLorey’s BA-weighted Height ft [LHT_ft] = 21.4980 + [ElevP90] * 0.7242

  35. Regression modelsLorey’s BA-weighted Height ft

  36. Regression modelsLive Basal Area sqft/ac [LBA_sqftac] = sqr ( -5.0579 + [ElevSD] * -0.4280 + [ElevP95] * 0.2307 + [PC1stRtsCC] * 0.1039) + 2.809

  37. Regression modelsLive Basal Area sqft/ac

  38. Red areas have LIDAR predictor values >+/-10% beyond the range of the ground plots Greater than +/- 10% beyond ground plot LIDAR Metrics

  39. Example ArcGIS Calculations • Any of the LIDAR layers can be used in GIS to calculate combinations of forest structure variables

  40. Live Basal Area > 200 sqft/ac

  41. Canopy Cover 80%+ and Height 100ft+

  42. Current limitations on using existing LIDAR data • No coordination within natural resource organizations at any level for: • LIDAR specifications necessary for forest measurements • Ground plot measurements when large, multi-agency LIDAR acquisitions occur Missed opportunity to leverage existing LIDAR

  43. Possible problems with use of FIA plots for LIDAR projects • Plots not georeferenced well enough • Not enough plots measured in area within 1-2 years of LIDAR acquisition • Plot layout not well designed for use with high-resolution remote sensing data

  44. Future for LIDAR in forest measurement? • Faster, cheaper, better LIDAR data, but doesn’t solve ground plot problems • Multi-temporal LIDAR datasets for change analysis • Multispectral LIDAR for species classification • New satellite-based systems for sampling • Beyond LIDAR—other 3D sensors (IFSAR,etc.)

  45. LIDAR software DEMO Thurs 2009 Savannah River DOE Site LIDAR Project

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