Photogrammetric UAV Mapping of Terrain under Dense Coastal Vegetation: An Object-Oriented Classification Ensemble Algorithm for Classification and Terrain Correction

Photogrammetric UAV sees a surge in use for high-resolution mapping, but its use to map terrain under dense vegetation cover remains challenging due to a lack of exposed ground surfaces. This paper presents a novel object-oriented classification ensemble algorithm to leverage height, texture and con...

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Bibliographic Details
Published in:Remote sensing (Basel, Switzerland) Switzerland), 2017-11, Vol.9 (11), p.1187
Main Authors: Meng, Xuelian, Shang, Nan, Zhang, Xukai, Li, Chunyan, Zhao, Kaiguang, Qiu, Xiaomin, Weeks, Eddie
Format: Article
Language:English
Subjects:
Aerial surveys
Algorithms
Classification
classification correction
classification ensemble
coastal topographic mapping
Environmental restoration
Error correction
high resolution
Learning algorithms
Machine learning
Mapping
Object oriented programming
object-oriented analysis
photogrammetric UAV
Photogrammetry
Problem solving
Restoration
terrain correction
Terrain mapping
Vegetation
Vegetation cover
wetland restoration
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Summary:Photogrammetric UAV sees a surge in use for high-resolution mapping, but its use to map terrain under dense vegetation cover remains challenging due to a lack of exposed ground surfaces. This paper presents a novel object-oriented classification ensemble algorithm to leverage height, texture and contextual information of UAV data to improve landscape classification and terrain estimation. Its implementation incorporates multiple heuristics, such as multi-input machine learning-based classification, object-oriented ensemble, and integration of UAV and GPS surveys for terrain correction. Experiments based on a densely vegetated wetland restoration site showed classification improvement from 83.98% to 96.12% in overall accuracy and from 0.7806 to 0.947 in kappa value. Use of standard and existing UAV terrain mapping algorithms and software produced reliable digital terrain model only over exposed bare grounds (mean error = −0.019 m and RMSE = 0.035 m) but severely overestimated the terrain by ~80% of mean vegetation height in vegetated areas. The terrain correction method successfully reduced the mean error from 0.302 m to −0.002 m (RMSE from 0.342 m to 0.177 m) in low vegetation and from 1.305 m to 0.057 m (RMSE from 1.399 m to 0.550 m) in tall vegetation. Overall, this research validated a feasible solution to integrate UAV and RTK GPS for terrain mapping in densely vegetated environments.
ISSN:2072-4292
2072-4292
DOI:10.3390/rs9111187