The Progress of Survey Techniques in Underwater Sites: The Case Study of Cape Stoba Shipwreck

Costa, Elisa

doi:10.5194/isprs-archives-xlii-2-w10-69-2019

Cited by 8 publications

(5 citation statements)

References 16 publications

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“…Photogrammetry taking more than one optical medium into account is known as multimedia photogrammetry. Many commercial and public use cases of photogrammetry such as fish farming [3,4], industrial inspection tasks [5], archaeological tasks [6] or surveying of cultural heritage [7] take place underwater, thus deal with multimedia photogrammetry. In the case of underwater photogrammetry, usually, three media are present.…”

Section: Of 31mentioning

confidence: 99%

Impact of Stereo Camera Calibration to Object Accuracy in Multimedia Photogrammetry

2020

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Camera calibration via bundle adjustment is a well-established standard procedure in single-medium photogrammetry. When using standard software and applying the collinearity equations in multimedia photogrammetry, the effects of refractive interfaces are compensated in an implicit form, hence by the usual parameters of interior orientation. This contribution analyses different calibration strategies for planar bundle-invariant interfaces. To evaluate the effects of implicitly modelling the refractive effects within bundle adjustment, synthetic error-free datasets are simulated. The behaviour of interior, exterior, and relative orientation parameters is analysed using synthetic datasets free of underwater imaging effects. A shift of the camera positions of 0.2% of the acquisition distance along the optical axis can be observed. The relative orientation of a stereo camera shows systematic effects when the angle of convergence varies. The stereo baseline increases by 1% at 25° convergence. Furthermore, the interface is set up at different distances to the camera. When the interface is at 50% distance assuming a parallel camera setup, the stereo baseline also increases by 1%. It becomes clear that in most cases the implicit modelling is not suitable for multimedia photogrammetry due to geometrical errors (scaling) and absolute positioning errors. Explicit modelling of the refractive interfaces is implemented into a bundle adjustment and is also used to analyse calibration parameters and deviations in object space. Real experiments show that it is difficult to separate the effects of implicit modelling, since other effects, such as poor image measurements, affect the final result. However, trends can be seen, and deviations are quantified.

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Section: Of 31mentioning

confidence: 99%

Impact of Stereo Camera Calibration to Object Accuracy in Multimedia Photogrammetry

2020

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“…These aspects are important in a variety of underwater applications, ranging from navigation with optical sensors to measuring objects and sea species underwater, such as offshore pillars, welding seams (Ekkel et al 2015), nuclear power plants (Przybilla et al 1990), reefs (Rossi et al 2021;Rofallski et al 2020a), wrecks (Drap et al 2015;Prado et al 2019;Rofallski et al 2020b) or archaeological sites (Costa 2019). Furthermore, multimedia photogrammetry plays an important role in tasks on land, e.g.…”

Section: Introductionmentioning

confidence: 99%

An Efficient Solution to Ray Tracing Problems in Multimedia Photogrammetry for Flat Refractive Interfaces

Rofallski

Lühmann

2022

PFG

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Understanding and considering refraction effects are important parts of the demanding task of multimedia photogrammetry, especially with planar interfaces, so-called ”flat ports”. Yet, it remains challenging to determine reliable calibration results that are both quickly acquired and physically interpretable. In this contribution, a novel object-based optimization algorithm, relying on ray tracing methods, is introduced. It enables calibrating physical parameters of all involved refractive properties with reduced computational effort, compared to other standard algorithms in ray tracing. We show that this solution produces equally accurate results as other ray tracing approaches while improving processing speed by a factor of approximately ten and providing a statistical metric in object space. Furthermore, we show in a laboratory investigation that explicit calibration of refractive properties is crucial even with orthogonally aligned bundle-invariant interfaces for highest accuracy, as accuracy in object space is decreased by about 10% with implicit calibration. With deviation from orthogonality by about ten degrees this decreases even further to almost no useful results and accuracy loss of more than 50% compared to explicit calibration results.

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“…The 3D Trilateration procedure is used for obtaining metrically correct products, such as dense point clouds, DEMs, and orthophotos, and is based on a network of ground control points (GCPs) whose linear distance and depth measurements must be known [38]. A typical implementation underwater is carried out by measuring distances with a tape and taking depth measurements with a dive computer [51][52][53]. An improved technique that can achieve sub-centimetric accuracy via underwater photogrammetry was recently demonstrated in the context of long-term monitoring of coral growth in French Polynesia [19,52].…”

Section: Georeferencing and Scaling Techniquesmentioning

confidence: 99%

Assessing Seagrass Restoration Actions through a Micro-Bathymetry Survey Approach (Italy, Mediterranean Sea)

Rende

Bosman

Menna

et al. 2022

Water

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Underwater photogrammetry provides a means of generating high-resolution products such as dense point clouds, 3D models, and orthomosaics with centimetric scale resolutions. Underwater photogrammetric models can be used to monitor the growth and expansion of benthic communities, including the assessment of the conservation status of seagrass beds and their change over time (time lapse micro-bathymetry) with OBIA classifications (Object-Based Image Analysis). However, one of the most complex aspects of underwater photogrammetry is the accuracy of the 3D models for both the horizontal and vertical components used to estimate the surfaces and volumes of biomass. In this study, a photogrammetry-based micro-bathymetry approach was applied to monitor Posidonia oceanica restoration actions. A procedure for rectifying both the horizontal and vertical elevation data was developed using soundings from high-resolution multibeam bathymetry. Furthermore, a 3D trilateration technique was also tested to collect Ground Control Points (GCPs) together with reference scale bars, both used to estimate the accuracy of the models and orthomosaics. The root mean square error (RMSE) value obtained for the horizontal planimetric measurements was 0.05 m, while the RMSE value for the depth was 0.11 m. Underwater photogrammetry, if properly applied, can provide very high-resolution and accurate models for monitoring seagrass restoration actions for ecological recovery and can be useful for other research purposes in geological and environmental monitoring.

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The Progress of Survey Techniques in Underwater Sites: The Case Study of Cape Stoba Shipwreck

Cited by 8 publications

References 16 publications

Impact of Stereo Camera Calibration to Object Accuracy in Multimedia Photogrammetry

Impact of Stereo Camera Calibration to Object Accuracy in Multimedia Photogrammetry

An Efficient Solution to Ray Tracing Problems in Multimedia Photogrammetry for Flat Refractive Interfaces

Assessing Seagrass Restoration Actions through a Micro-Bathymetry Survey Approach (Italy, Mediterranean Sea)

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