#Garmin homeport 2.2 manual

Each side of the image in (b) has a slant range = 75 m. (a) Spring-type SGD amidst the sparse-type SGD in Tingloy, at 9 m depth (b) 800-m side scan sonar image acquired using RGSSS, nadir zone/boat rack indicated by blue arrow (c) Zoomed in view of the sonar image with 50-m bubbly SGD field enclosed by the blue broken lines, spring-type SGD is indicated by the red arrow. Spring-type in sparse-type SGD field in Tingloy. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) (See description of SGD and other figures in text). The white, broken lines outline the wake of the passing boat yellow arrows indicate parts of benthos. In (g), the blue arrow indicates the nadir zone or the transducer track. CTD profiles: (k) Salinity, (l) temperature, (m) conductivity. RGES sonar images with identified SGD enclosed by blue broken lines in all panels -Garmin: (e) 77 kHz, (f) 200 kHz Humminbird: (g) side scan image (455 kHz), (h) down scan image (83 kHz), (i) down scan image (455 kHz), (j) down scan image (200 kHz). Each side of the image has a slant range = 75 m. (c) 120-m side scan sonar image acquired using RGSSS, showing the coralline seafloor, nadir zone or boat track (blue arrow), and the identified SGD (d) Zoomed in view of the RGSSS image with SGD, enclosed by the blue broken lines red arrows indicate transducer trail. (a) Frequent gas discharges at depth <5 m (b) sporadic gas discharge (enclosed in red boxes) from depths of about 7 m to 8 m. Additional research on areas with water-dominated discharge but no bubbling is recommended. These results showed that RGES provides a good alternative for more efficient and cost-effective preliminary coastal SGD works. Three types of known SGD occurrence were identified and characterized based on acoustic behavior and spatial distribution: 1) sparse, discrete and sporadic discharge over wide area, 2) curtain, high and continuous bubble concentrations from widespread discharge, and 3) spring, direct bubble discharge from intense seafloor degassing at a single point source. Hence, showing more accurate point sources of SGD.

#Garmin homeport 2.2 manual

The clusters of bubbly discharges have higher backscatter strength than the water column noise, resulting in the definitive and convenient manual detection of SGD features. Lower frequencies (77/83 kHz) of RGESs showed more distinct acoustic signatures of bubbly SGD, as these were nearly the same as the effective resonance frequency of the bubbles. The use of RGES was validated using a research-grade side scan sonar (RGSSS), continuous resistivity profiling, conductivity-temperature-depth casting, and MantaCam and SCUBA diving surveys.

Standard and systematic methodologies for efficient imaging and processing were established. This study explores the capability and applicability of low-cost, off-the-shelf, recreational-grade echosounders (RGES) to image different types and locate point sources of bubbly coastal SGD. Despite the growing knowledge on the significance of submarine groundwater discharge (SGD), mapping its occurrence is a continuing challenge.