ADCP current measurements (38 kHz) during RV MARIA S. MERIAN cruise MSM108

Upper-ocean velocities along the cruise track of Maria S. Merian cruise MSM108 were continuously collected by a vessel-mounted Teledyne RD Instruments 38 kHz Ocean Surveyor ADCP.
The transducer was located at 6.0 m below the water line. The instrument was operated in narrowband mode with 32 m bins and a blanking distance of 16.0 m, while 50 bins were recorded using a pulse of 2.81 s.
The ship's velocity was calculated from position fixes obtained by the Global Positioning System (GPS). Heading, pitch and roll data from the ship's gyro platforms and the navigation data were used by the data acquisition software VmDas internally to convert ADCP velocities into earth coordinates.
Accuracy of the ADCP velocities mainly depends on the quality of the position fixes and the ship's heading data. Further errors stem from a misalignment of the transducer with the ship's centerline.
Data post-processing included water track calibration of the misalignment angle (0.38° +/- 0.6278°) and scale factor (0.9954 +/- 0.0083) of the Ocean Surveyor signal. The average interval was set to 120 s.
Velocity quality flagging is based on following threshold criteria: abs(UC) or abs(VC) > 1.5 m/s, rms(UC_z) or rms(VC_z) > 0.3.

本数据集连续采集了Maria S. Merian号科考航次MSM108航线沿线的上层海洋流速数据，采集设备为安装于科考船的泰莱迪恩RD仪器（Teledyne RD Instruments）38 kHz Ocean Surveyor型声学多普勒流速剖面仪（ADCP）。
该仪器的换能器安装于吃水线下方6.0米处。仪器采用窄带工作模式，测层间距为32米，盲区距离为16.0米；本次采集共记录50个测层，脉冲时长为2.81秒。
船舶自身的运动速度通过全球定位系统（Global Positioning System, GPS）获取的位置定位数据计算得到。船舶陀螺平台提供的航向、俯仰及横滚数据，与导航数据一同被数据采集软件VmDas内部调用，用于将ADCP测得的相对流速转换为地球坐标系下的绝对流速。
ADCP流速数据的精度主要取决于位置定位数据与船舶航向数据的质量，此外还存在因换能器与船舶中心线未对准所引入的额外误差。
数据后处理环节包含对Ocean Surveyor信号的失准角（0.38° ± 0.6278°）与比例因子（0.9954 ± 0.0083）进行水迹校准，本次处理的平均采样间隔设为120秒。
流速数据的质量标记遵循以下阈值标准：当|UC|或|VC|大于1.5 m/s，或UC_z的均方根误差或VC_z的均方根误差大于0.3时，即判定为不合格数据。