2006 Fiscal Year Final Research Report Summary
Measurement of forest biomass by combined use of an air-borne laser scanner and digital aerial photographs
| Project/Area Number |
17510008
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | Kyoto University |
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Principal Investigator |
TAMURA Masayuki Kyoto University, Graduate School of Engineering, Professor (90109900)
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| Co-Investigator(Kenkyū-buntansha) |
OGUMA Hiroyuki Center of Global Environmental Research, National Institute for Environmental Studies, Senior researcher (10342734)
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| Project Period (FY) |
2005 – 2006
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| Keywords | laser scanner / digital aerial photographs / tree top / tree crown / tree height / number of trees / biomass |
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| Research Abstract |
A method has been developed for measuring tree heights, number of trees and forest biomass by combined use of an air-borne laser scanner and digital aerial photographs. Main results of the study are as follows:
1. A digital surface model (DSM) and a digital terrain model (DTM) were created from the laser first and last pulses respectively. The accuracy of DTM was largely improved by selecting the lowest last-pulse points in each 5x5-m mesh and interpolating them in 0.2x0.2-m grids. A forest digital crown model (DCM) was produced by subtracting DTM from DSM.
2. Aerial photos were orthorectified and registered to the laser DSM with high precision. Overlaying tree tops derived from laser data over the registered orthophotos proved to be useful for verifying the accuracy of tree-top extraction.
3. Tree tops were extracted by applying the local-maximum-filter to the laser DCM. The best performance was attained by a circular filter of a radius 0.6 m. It was found that the laser measurement could extract the tree tops of high layer trees (trees with heights > 11 m) but was not capable of extracting middle or low layer trees.
4. Tree crowns are identified by applying the watershed method to the laser DCM. The relationships between tree heights and crown sizes were described for each tree species, i. e. larch, spruce and hardwood, by exponential curves.
5. Forest biomass was calculated from the laser-derived tree heights and compared to the results of field investigation. The laser-derived biomass was found to be underestimation of the total biomass but agree well with the biomass of the high layer trees.
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