期刊名称：ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
印刷版ISSN：2194-9042
电子版ISSN：2194-9050
出版年度：2010
卷号：XXXVIII - Part 7A
页码：1-6
出版社：Copernicus Publications
摘要：During the last decade,there have been numerous scientific studies verifying the accuracy of digital elevation models(DEM)derivedfromairborne laser scanning (ALS). Since ALS hasincreasinglybeen used fornationwide digital elevation model data acquisition,optimizingALS acquisition parameters is a topic of interest to national landsurveys.In particular, the effect ofthescanning angleand biomasson elevation-model accuracy needs further studyinheavily-forested areas. The elevation-modelaccuracyis affected by,for example,the number of pulses hittingthe ground,footprint size,terrain slope and, especially,vegetation.In order to betterunderstand the effect ofthebiomass and scanning angleon the penetration rateof ALSsignal through canopyand give furthersupport to ALS studies, especially for scanning angles beyond 15 degrees ofthenadirpoint,we conductedan indoor experimentusing small sprucetreesto represent forest canopy.Theindoorexperimentallowedusto measurethebiomass reference accurately.We used manual thinning to produce various levels of biomassandscissor liftasthecarrying platform.Wemeasuredthe weight ofevery tree and the totalbiomassof treesafter each thinning phase.We removed the materialhomogeneously from the trees,startingfrom the latest shoots.We used aFAROlaser scanner in the experiment and attacheditto the scissor lift.We scanned theexperimental plot from four altitudes (about 3, 5, 7 and 9 m) andatsix biomass levels (about 0, 6, 9, 14, 20 and 25 kg).The resultsshow thatsignaltransmittancethrough spruce trees is a function of biomass and scanning angle, butthatthescanning angleonlyhasa minor effect on the results.Biomass is the major parameter in determiningthe quality of theelevation model.While the resultsrequire furtherairborne experiments to befullyconfirmed,they doimply thatascanning anglegreaterthan 15 degrees can beapplied inregions having low and moderate biomass, and due to the significant effect of the biomass on the transmittance, theairborne scanning missionsmustbe carefullyspecifiedin heavily-forested terrain.We also found that terrestrial laser scanningexperimentsperformed in an indoorlaboratory-type settingyielded arelatively good understanding ofthebasic behaviour ofandinteraction betweenthe target and laser scanningrather easily,butthatitwill beconsiderably more difficult toobtainsimilar resultsinareal-life experiment due to limited accuracywhen collectingthereference data
