Where's the ground surface? Elevation bias in LIDAR-derived digital elevation models due to dense vegetation in Oregon tidal marshes Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/2r36v250n

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • Light Detection and Ranging (LIDAR) is a powerful resource for coastal and wetland managers and its use is increasing. Vegetation density and other land cover characteristics influence the accuracy of LIDAR-derived ground surface digital elevation models; however, the degree to which wetland land cover biases LIDAR estimates of the ground surface is largely unknown. The minimum-bin LIDAR gridding technique has been proposed as a way to mitigate dense vegetation interference to generate LIDAR-derived digital elevation models (DEM). Past research has focused on the ability to resolve the marsh plain elevation and only limited research has investigated the overall DEM accuracy across the landscape using a wide range of cell sizes and land cover classes. I compared LIDAR-derived DEM accuracy across a 174 ha tidal wetland restoration site with a mix of native wetland and non-native agricultural pasture species. I found an optimum cell size of 1.4 m (1.96 m²) with a mean positive bias of 4.5 cm and a mean absolute error of 24.3 cm. At cell sizes smaller than the optimum, vegetation interferes with the LIDAR sensor and positively biases DEM models. At cell sizes larger than 1.4 m, the DEM captures and favors low features within the landscape, such as channels and ditches, which thereby degrade overall DEM performance. In addition, I investigated LIDAR interference by twelve common tidal wetland vegetation associations across six Oregon estuaries, using survey-grade Global Positioning System (GPS) measurements of the wetland surface and quantitative vegetation data (percent cover by species) for each measurement location. The fundamental vertical accuracy (FVA) of the LIDAR datasets was 4.5 cm root mean square error (RMSE) and had no consistent positive or negative bias in open landcover. Within wetland vegetation communities, my results suggest that LIDAR estimates of the ground surface in tidal wetlands are typically 10 cm to 30 cm above GPS measurements. Plant associations dominated by Carex obnupta and Carex lyngbyei exhibited the largest discrepancy between LIDAR and GPS measurements (mean discrepancies 36.6 cm and 48.8 cm respectively). The smallest errors observed in the study were about 10 cm to 11 cm and occurred in several different plant associations, including two low tidal marsh associations dominated by a mixture of Deschampsia cespitosa, Distichlis spicata, Sarcocornia perennis and Jaumea carnosa. These results suggest that the minimum-bin gridding technique for LIDAR may mitigate vegetation interference by densely vegetated land covers within LIDAR-derived DEM. However, care should be taken to select an appropriate cell size and validate the results before relying on the DEM for analysis. My research yields new information for coastal LIDAR users and increases our understanding of uncertainty in LIDAR-derived datasets to improve the ability to accurately evaluate and manage coastal environments.
Resource Type
Date Available
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Non-Academic Affiliation
Keyword
Subject
Rights Statement
Peer Reviewed
Language
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Laura Wilson(laura.wilson@oregonstate.edu) on 2014-01-17T00:18:43Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: bb87e2fb4674c76d0d2e9ed07fbb9c86 (MD5) EwaldMichaelJ2013.pdf: 7491994 bytes, checksum: b75fdc53bc59296c94fc2787b70339e3 (MD5)
  • description.provenance : Submitted by Michael Ewald (ewaldm@onid.orst.edu) on 2013-12-29T00:59:58Z No. of bitstreams: 2 license_rdf: 1536 bytes, checksum: df76b173e7954a20718100d078b240a8 (MD5) EwaldMichaelJ2013.pdf: 7491994 bytes, checksum: b75fdc53bc59296c94fc2787b70339e3 (MD5)
  • description.provenance : Made available in DSpace on 2014-01-17T00:18:43Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: bb87e2fb4674c76d0d2e9ed07fbb9c86 (MD5) EwaldMichaelJ2013.pdf: 7491994 bytes, checksum: b75fdc53bc59296c94fc2787b70339e3 (MD5) Previous issue date: 2013-11-18
  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2014-01-14T17:52:42Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: bb87e2fb4674c76d0d2e9ed07fbb9c86 (MD5) EwaldMichaelJ2013.pdf: 7491994 bytes, checksum: b75fdc53bc59296c94fc2787b70339e3 (MD5)
  • description.provenance : Submitted by Michael Ewald (ewaldm@onid.orst.edu) on 2014-01-14T17:27:23Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: bb87e2fb4674c76d0d2e9ed07fbb9c86 (MD5) EwaldMichaelJ2013.pdf: 7491994 bytes, checksum: b75fdc53bc59296c94fc2787b70339e3 (MD5)
  • description.provenance : Rejected by Julie Kurtz(julie.kurtz@oregonstate.edu), reason: Rejecting because the actual thesis is missing the page numbers. Once revised, log back into ScholarsArchive and go to the upload page. Replace the attached file with the revised file and resubmit. Thanks, Julie on 2014-01-06T21:57:45Z (GMT)

Relationships

Parents:

This work has no parents.

Last modified

Downloadable Content

Download PDF

Items