CEAMARC-CASO 12kHz Bathymetry - data collected from voyage 3, 2007-2008 of the Aurora Australis

Bathymetry data was collected using a Simrad EK60 echosounder. The sample data have been corrected for the relative locations of GPS antenna, transducers and waterline. A sound-speed value of 1500 m/s was applied when calculating depth.The seafloor depth itself was defined firstly as the depth of the sounder-detected bottom minus 10m (contact Simrad for more information about their bottom-detection algorithm), and then modified manually where necessary to ensure that the line followed the seafloor as perceived by eye from the echogram. This is therefore a subjective process, and the true seafloor depth may vary from the perceived depth by several hundred metres in the worst cases. The greatest uncertainties are typically at greater depths, e.g. greater than 1000 m.This seafloor depth line therefore refers to the approximate depth (not range from transducer) of the seafloor less 10 m, i.e. 10 m should be added to the 'depth' values in the *.CSV file to give the 'true' seafloor depth.Depths greater than 5000 m are not available due to the 12 kHz data not being logged any deeper than this.These data are preliminary and subject to change.Bathymetry data was exported during the voyage by Belinda Ronai. Post voyage enquiries however should be directed to Toby Jarvis.

本水深测量数据采用西姆拉德EK60回声测深仪（Simrad EK60 echosounder）采集。样本数据已针对GPS天线、换能器与水线的相对位置完成校正。计算水深时采用了1500 m/s的声速值。海底水深最初定义为回声测深仪探测到的海底深度减去10米（如需了解其海底探测算法的更多细节，请联系西姆拉德（Simrad）），随后可根据需要手动调整，以确保轨迹线与回声图（echogram）目视识别的海底形态相匹配。该过程具有主观性，在极端情况下，实际海底水深与目视识别的水深可能存在数百米的偏差。最大的不确定性通常出现在较深水域，例如水深超过1000米的区域。此处的海底水深轨迹线指的是海底近似水深（非换能器到海底的距离）减去10米，即需将*.CSV文件中的“depth”字段值加上10米，方可得到“实际”海底水深。由于12千赫兹（12 kHz）数据的记录深度上限为5000米，因此无法获取水深超过5000米的相关数据。本数据集为初步成果，后续可能进行调整。本次航行期间的水深数据由贝琳达·罗奈（Belinda Ronai）导出，航行结束后的相关咨询请联系托比·贾维斯（Toby Jarvis）。