UAV Derived Information Applied to the Study of Slow-changing Morphology in Dune Systems

Bastos, Ana Pestana; Lira, Cristina; Calvao, J.; Catalão, João; Andrade, César; Pereira, Ana Jú; Taborda, Rui; Rato, Daniela; Pinho, Pedro; Correia, Otília

doi:10.2112/si85-046.1

Cited by 10 publications

(12 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ground pixel distance was set at 0.03 m which resulted in a flight level of~100 m above take-off level. Vegetated points were removed rather than lowered (as suggested by Bastos, et al [62]) because of the difficulty in knowing variation in vegetation height over the larger study area. Finally, each point cloud was interpolated onto the same 0.5 m resolution regular grid to create a DTM from which further analysis was conducted.…”

Section: Survey Methodologymentioning

confidence: 99%

“…One difficulty of using UAVs for coastal dune studies is how to correct for vegetation in the point cloud when sediment budgets and landform evolution are of interest. Bastos, et al [62], trialled two different methodologies: orthomosaics were used to identify vegetation areas and then either the vegetation areas were removed from the digital surface map, (DSM), before re-interpolating to a digital terrain map, (DTM), or the DSM was converted to a DTM by reducing elevations of vegetated areas by a set amount. Statistically, the second method performed better, although the surface was noisier that the first method.…”

Section: Introductionmentioning

confidence: 99%

“…Statistically, the second method performed better, although the surface was noisier that the first method. Bastos, et al [62] also point out the difficulty of knowing the correct height for vegetation in order to adjust the elevation. In this study, we take a different approach, (discussed in Section 2.2.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Spatial Variation in Coastal Dune Evolution in a High Tidal Range Environment

et al. 2020

View full text Add to dashboard Cite

Coastal dunes have global importance as ecological habitats, recreational areas, and vital natural coastal protection. Dunes evolve due to variations in the supply and removal of sediment via both wind and waves, and on stabilization through vegetation colonization and growth. One aspect of dune evolution that is poorly understood is the longshore variation in dune response to morphodynamic forcing, which can occur over small spatial scales. In this paper, a fixed wing unmanned aerial vehicle (UAV), is used to measure the longshore variation in evolution of a dune system in a megatidal environment. Dune sections to the east and west of the study site are prograding whereas the central portion is static or eroding. The measured variation in dune response is compared to mesoscale intertidal bar migration and short-term measurements of longshore variation in wave characteristics during two storms. Intertidal sand bar migration is measured using satellite imagery: crescentic intertidal bars are present in front of the accreting portion of the beach to the west and migrate onshore at a rate of 0.1–0.2 m/day; episodically the eastern end of the bar detaches from the main bar and migrates eastward to attach near the eastern end of the study area; bypassing the central eroding section. Statistically significant longshore variation in intertidal wave heights were measured using beachface mounted pressure transducers: the largest significant wave heights are found in front of the dune section suffering erosion. Spectral differences were noted with more narrow-banded spectra in this area but differences are not statistically significant. These observations demonstrate the importance of three-dimensionality in intertidal beach morphology on longshore variation in dune evolution; both through longshore variation in onshore sediment supply and through causing longshore variation in near-dune significant wave heights.

show abstract

Section: Survey Methodologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Spatial Variation in Coastal Dune Evolution in a High Tidal Range Environment

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Therefore, the production of Digital Terrain Models (DTMs) is a primary tool for the monitoring of coastal erosion, as well as for developing detailed and high-resolution numerical simulation models able to predict the impact of storms, sea level rise, and flooding risk [1]. Dune systems are characterized by high dynamics in which the morphology changes rapidly and where high accuracy is required [2] to describe the evolution of small dunes [3].…”

Section: Introductionmentioning

confidence: 99%

Coastal Mapping Using DJI Phantom 4 RTK in Post-Processing Kinematic Mode

Taddia

Stecchi²,

Pellegrinelli

2020

Drones

126

View full text Add to dashboard Cite

Topographic and geomorphological surveys of coastal areas usually require the aerial mapping of long and narrow sections of littoral. The georeferencing of photogrammetric models is generally based on the signalization and survey of Ground Control Points (GCPs), which are very time-consuming tasks. Direct georeferencing with high camera location accuracy due to on-board multi-frequency GNSS receivers can limit the need for GCPs. Recently, DJI has made available the Phantom 4 Real-Time Kinematic (RTK) (DJI-P4RTK), which combines the versatility and the ease of use of previous DJI Phantom models with the advantages of a multi-frequency on-board GNSS receiver. In this paper, we investigated the accuracy of both photogrammetric models and Digital Terrain Models (DTMs) generated in Agisoft Metashape from two different image datasets (nadiral and oblique) acquired by a DJI-P4RTK. Camera locations were computed with the Post-Processing Kinematic (PPK) of the Receiver Independent Exchange Format (RINEX) file recorded by the aircraft during flight missions. A Continuously Operating Reference Station (CORS) located at a 15 km distance from the site was used for this task. The results highlighted that the oblique dataset produced very similar results, with GCPs (3D RMSE = 0.025 m) and without (3D RMSE = 0.028 m), while the nadiral dataset was affected more by the position and number of the GCPs (3D RMSE from 0.034 to 0.075 m). The introduction of a few oblique images into the nadiral dataset without any GCP improved the vertical accuracy of the model (Up RMSE from 0.052 to 0.025 m) and can represent a solution to speed up the image acquisition of nadiral datasets for PPK with the DJI-P4RTK and no GCPs. Moreover, the results of this research are compared to those obtained in RTK mode for the same datasets. The novelty of this research is the combination of a multitude of aspects regarding the DJI Phantom 4 RTK aircraft and the subsequent data processing strategies for assessing the quality of photogrammetric models, DTMs, and cross-section profiles.

show abstract

“…The intertidal hydrodynamics and morphology are progressively changing over time mostly due to the rise of the mean sea level in the last centuries, but also due to other severe processes, such as floods or storms [5][6][7][8]. Monitoring intertidal areas can provide updated topographic models and predict further impacts on morphodynamics and on ecosystems [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Intertidal Bathymetry Extraction with Multispectral Images: A Logistic Regression Approach

2020

Self Cite

View full text Add to dashboard Cite

In this study, a methodology to estimate the intertidal bathymetry from multispectral remote sensing images is presented. The technique is based on the temporal variability of the water and the intertidal zone reflectance and their correlation with the tidal height. The water spectral behavior is characterized by high absorption at the infrared (IR) band or radiation with higher wavelengths. Due to tidal cycles, pixels on the intertidal zone have higher temporal variability on the near IR spectral reflectance. The variability of IR reflectivity in time is modeled through a sigmoid function of three parameters, where the inflection parameter corresponds to the pixel elevation. The methodology was tested at the Tagus river estuary in Lisbon, Portugal, and at the Bijagós archipelago, in the West African nation of Guinea-Bissau. Multispectral images from Sentinel-2 satellites were used, after atmospheric corrections from ACOLITE processor and the derived bathymetric model validated with in situ data. The presented method does not require additional depth data for calibration, and the output can generate intertidal digital elevation models at 10 m spatial resolution, without any manual editing by the operator. The results show a standard deviation of 0.34 m at the Tagus tidal zone, with −0.50 m bias, performing better than the Stumpf ratio transform algorithm, also applied to the test areas to derive intertidal bathymetry. This methodology can be used to update intertidal elevation models with clear benefits to monitoring of intertidal dynamics, morphodynamic modeling, and cartographic update.

show abstract

UAV Derived Information Applied to the Study of Slow-changing Morphology in Dune Systems

Cited by 10 publications

References 4 publications

Spatial Variation in Coastal Dune Evolution in a High Tidal Range Environment

Spatial Variation in Coastal Dune Evolution in a High Tidal Range Environment

Coastal Mapping Using DJI Phantom 4 RTK in Post-Processing Kinematic Mode

Intertidal Bathymetry Extraction with Multispectral Images: A Logistic Regression Approach

Contact Info

Product

Resources

About