A low-cost, autonomous mobile platform for limnological investigations, supported by high-resolution mesoscale airborne imagery

Barry, David Andrew; Liardon, Jean-Luc; Paccaud, Philippe; Klaus, Pascal; Shaik, Nawaaz S. Gujja; Rahaghi, Abolfazl Irani; Zulliger, Ludovic; Béguin, Jérôme; Geissmann, Beat Marcel; Tulyakov, Stepan; Иванов, А. Е.; Wynn, Htet Kyi; Lemmin, Ulrich

doi:10.1371/journal.pone.0210562

Cited by 6 publications

(8 citation statements)

References 53 publications

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“…This allows for real‐time data control, correction, and analysis on the boat that accompanies ZiviCat and on which the winch for BLIMP is mounted. Details of the systems and sensors are presented in Barry et al (). It should be noted that the whole measurement platform was continuously moving during the missions to cover the surface area along a predetermined trajectory.…”

Section: Methodsmentioning

confidence: 99%

Surface Water Temperature Heterogeneity at Subpixel Satellite Scales and Its Effect on the Surface Cooling Estimates of a Large Lake: Airborne Remote Sensing Results From Lake Geneva

2019

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The dynamics of spatial heterogeneity of lake surface water temperature (LSWT) at subpixel satellite scale O(1 m) and its effect on the surface cooling estimation at typical satellite pixel areas O(1 km 2 ) were investigated using an airborne platform. The measurements provide maps that revealed spatial LSWT variability with unprecedented detail. The cold season data did not show significant LSWT heterogeneity and hence no surface cooling spatial variability. However, based on three selected daytime subpixel-scale maps, LSWT patterns showed a variability of >2°C in the spring and >3.5°C in the summer, corresponding to a spatial surface cooling range of >20 and >40 W/m 2 , respectively. Due to the nonlinear relationship between turbulent surface heat fluxes and LSWT, negatively skewed LSWT distributions resulted in negatively skewed surface cooling patterns under very stable or predominantly unstable atmospheric boundary layer (ABL) conditions and positively skewed surface cooling patterns under predominantly stable ABL conditions. Implementing a mean spatial filter, the effect of area-averaged LSWT on the surface cooling estimation up to a typical satellite pixel was assessed. The effect of the averaging filter size on the mean spatial surface cooling values was negligible, except for predominantly stable ABL conditions. In that situation, a reduction of~3.5 W/m 2 was obtained when moving from high O(1 m) to low O(1 km) pixel resolution.Plain Language Summary Lake surface water temperature (LSWT) is one of the main parameters required for estimating surface cooling at the air-water interface and is also essential for understanding other processes (such as ecosystem dynamics, climate change, and numerical weather prediction) in lakes. Usually, surface cooling is determined from in situ point measurements or satellite images. Satellite thermal images resolve surface areas with a typical pixel resolution of O(1 km). Therefore, satellite data can depict large-scale thermal patterns. But can LSWT spatial variability be significant at subpixel satellite resolution over a large lake? What is the effect of such variability on area-averaged surface cooling estimates? To address these questions, a measurement system, including a balloon-launched airborne platform for thermography and a catamaran for in situ measurements along predefined tracks, was used for LSWT mapping and calibration. Surface cooling patterns were then estimated using a calibrated bulk model. Results showed insignificant LSWT heterogeneity and hence no surface cooling spatial variability during the cold seasons. However, a notable spatial variability of >2°C and > 3.5°C was found in spring and summer, respectively. The effect of LSWT heterogeneity on surface cooling variability was significant, in particular, when air-water temperature differences were close to 0.

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Section: Methodsmentioning

confidence: 99%

Surface Water Temperature Heterogeneity at Subpixel Satellite Scales and Its Effect on the Surface Cooling Estimates of a Large Lake: Airborne Remote Sensing Results From Lake Geneva

2019

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“…The sensor spar is located well forward of the catamaran to avoid hull disturbances. The ZiviCat also has positioning (RTK-GPS), stability (IMU), data recording, and communication systems, which allow for real-time data control, correction and analysis on the accompanying boat (Barry et al, 2019).…”

Section: Measurement Platforms For Physical Parametersmentioning

confidence: 99%

Effects of natural surfactants on the spatial variability of surface water temperature under intermittent light winds on Lake Geneva

2022

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The spatial variability of lake surface water temperature (LSWT) between smooth and rough surface areas and its potential association with the natural surfactant distribution in the surface microlayer were investigated for the first time in a lake. In spring 2019, two different field campaigns were carried out in Lake Geneva to measure: i) the enrichment factor of fluorescent dissolved organic matter (FDOM) as a proxy for biogenic surfactants, and ii) LSWT and near-surface water temperature profiles while simultaneously monitoring water surface roughness in both cases. Results indicate that, under intense incoming short-wave radiation and intermittent light wind conditions, the atmospheric boundary layer (ABL) was stable and the accumulation of heat due to short-wave radiation in near-surface waters was greater than heat losses by surface cooling, thus creating a diurnal warm layer with strong thermal stratification in the water near-surface layer. A threshold wind speed of 1.5 m s-1 was determined as a transition between different dynamic regimes. For winds just above 1.5 m s-1, the lake surface became patchy, and smooth surface areas (slicks) were more enriched with FDOM than rough areas (non-slick) covered with gravity-capillary waves (GCW). Sharp thermal boundaries appeared between smooth and rough areas. LSWT in smooth slicks was found to be more than 1.5°C warmer than in rough non-slick areas, which differs from previous observations in oceans that reported a slight temperature reduction inside slicks. Upon the formation of GCW in non-slick areas, the near-surface stratification was destroyed and the surface temperature was reduced. Furthermore, winds above 1.5 m s-1 continuously fragmented slicks causing a rapid spatial redistribution of LSWT patterns mainly aligned with the wind. For wind speeds below 1.5 m s‑1 the surface was smooth, no well-developed GCW were observed, LSWT differences were small, and strong near-surface stratification was established. These results contribute to the understanding and the quantification of air-water exchange processes, which are presently lacking for stable Atmospheric Boundary Layer conditions in lakes.

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“…In the second step, experimental validation was conducted using an autonomous catamaran developed in our laboratory [ 11 ]. The platform is about 5-m long by 2.5-m wide, and is embedded with numerous sensors for limnological measurements.…”

Section: Algorithmmentioning

confidence: 99%

“…It is configured as a standalone module that can be easily interfaced with existing platforms. The ASV used in this work is described elsewhere [ 11 ]. It provides power as well as continuous communication and monitoring over the 4G cellular network using the TCP/IP (i.e., internet, Transmission Control Protocol/Internet Protocol) protocol.…”

Section: Introductionmentioning

confidence: 99%

Obstacle detection for lake-deployed autonomous surface vehicles using RGB imagery

Paccaud

Barry

2018

PLoS ONE

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We describe and test an obstacle-detection system for small, lake-deployed autonomous surface vehicles (ASVs) that relies on a low-cost, consumer-grade camera and runs on a single-board computer. A key feature of lakes that must be accounted for is the frequent presence of the shoreline in images as well as the land-sky boundary. These particularities, along with variable weather conditions, result in a wide range of scene variations, including the possible presence of glint. The implemented algorithm is based on two main steps. First, possible obstacles are detected using an innovative gradient-based image processing algorithm developed especially for a camera with a low viewing angle to the water (i.e., the situation for a small ASV). Then, true and false positives are differentiated using correlation-based multi-frame analysis. The algorithm was tested extensively on a small ASV deployed in Lake Geneva. Under operational conditions, the algorithm processed 640×480-pixel images from a Raspberry Pi Camera at about 3—4 Hz on a Raspberry Pi 3 Model B computer. The present algorithm demonstrates that single-board computers can be used for effective and low-cost obstacle detection systems for ASVs operating in variable lake conditions.

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A low-cost, autonomous mobile platform for limnological investigations, supported by high-resolution mesoscale airborne imagery

Cited by 6 publications

References 53 publications

Surface Water Temperature Heterogeneity at Subpixel Satellite Scales and Its Effect on the Surface Cooling Estimates of a Large Lake: Airborne Remote Sensing Results From Lake Geneva

Surface Water Temperature Heterogeneity at Subpixel Satellite Scales and Its Effect on the Surface Cooling Estimates of a Large Lake: Airborne Remote Sensing Results From Lake Geneva

Effects of natural surfactants on the spatial variability of surface water temperature under intermittent light winds on Lake Geneva

Obstacle detection for lake-deployed autonomous surface vehicles using RGB imagery

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