Comparison of topographic information from various sources for engineering design

Goodwin, Alex Michael

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https://hdl.handle.net/2142/101605 Copy

Description

Title

Comparison of topographic information from various sources for engineering design

Author(s)

Goodwin, Alex Michael

Issue Date

2018-07-17

Director of Research (if dissertation) or Advisor (if thesis)

Bhattarai, Rabin

Department of Study

Engineering Administration

Discipline

Agricultural & Biological Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

Eutrophication, LiDAR, Resolution, Surveying

Abstract

The Natural Resources Conservation Service (NRCS) collaborates with many organizations in the state of Illinois to remediate the eutrophication problem in the Gulf of Mexico. To design the projects needed to combat eutrophication efficiently, topographic data will need to be readily available with a high standard of accuracy. One of the main targets for these projects is flat cropland where nutrients are moving through soil into streams and ultimately ending up in the Gulf of Mexico, contributing to the dead zone. Light detection and ranging (LiDAR) data have been collected across much of Illinois to serve this purpose. LiDAR has not yet been evaluated for flat cropland, though it shows promise based on its performance in other ecosystems. This study utilizes two resolutions of LiDAR that had been collected earlier, one at 4 points per square meter (ppsm) and a higher resolution at 8 ppsm. Total station and real time kinematic (RTK) surveys have also been conducted and the total station data are used as the standard by which LiDAR will be evaluated. Anecdotal experiences have suggested that LiDAR data appear accurate, but overall the elevations are uniformly too high or too low. The surfaces created by the different datasets appeared similar, but the average elevation values of the LiDAR were significantly different. This study investigates adjusting the data upwards or downwards and checking the overall accuracy. Overall, LiDAR data performed well in the comparisons. Before adjustment, the lower resolution LiDAR data had an RMSE of 9.54 cm when compared to the total station and the high-resolution LiDAR data had an RMSE of 9.26 cm. After adjusting the LiDAR to a lower average elevation value, the RMSE values dropped to 3.22 cm and 3.21 cm for the lower resolution LiDAR and high resolution LiDAR datasets respectively. RTK surveys did not yield datasets that improved significantly after adjustments, but performed well regardless. After adjustment, RTK datasets performed very similarly to the adjusted LiDAR datasets. Project designs that accept RTK survey data would be able to use LiDAR data due to the similarity in accuracy between the datasets. Special consideration should be taken to check older sets of LiDAR data, since RTK survey data would be used shortly after correction and the LiDAR data would be available for longer time spans. Erosion that occurred since data collection took place may invalidate the data. With LiDAR data gathered in nearly every county in Illinois, topographic data are readily available, depending on the level of accuracy required for design, for any organization looking to design conservation projects for farmlands may be able to use without having to hire surveying crews.

Graduation Semester

2018-08

Type of Resource

text

Permalink

http://hdl.handle.net/2142/101605

Copyright and License Information

Copyright 2018 Alex Goodwin

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