Calibrated DTS data, Maisbich, 2010-07

Calibrated fibre optic Distributed Temperature Sensing (DTS) data, Maisbich, Luxemburg Parent item: Calibrated fibre optic Distributed Temperature Sensing (DTS) data, Maisbich Explanation of the calibration procedure of the DTS derived temperatures in the Maisbich river, Luxembourg. Note that it only corrects offsets orriginating from the DTS device (Halo, Sensornet, UK). It does NOT correct for periods when the cable is not properly submerged in the stream. The DTS obtained temperatures were calibrated with five independent temperature loggers (TidbiT v2 Temp logger, HOBO, USA) located along the cable at 26, 395, 931, 1111 and 1270 m from the DTS desktop computer, respectively. Note that the investigated branch lies between 717 (V-notch weir Q3) and 1282 m (V-notch weir Q4) from the desktop computer. For each Tidbit temperature logger, which measured at a 6 min interval, a linear relation was determined between the DTS derived temperature and the difference between the TidbiT and DTS derived temperature for the period 4-Apr-2008 until 4-Dec-2008 (dT = a*T_DTS + b). For each Tidbit location a slope (a) and an offset (b) was determined: Tidbit Distance(m) a b T coolbox 26 -1.31 0,0974 T road 395 -0.49 0,0664 T Mai171u 931 -0.69 0,122 T Mai11u 1111 -0.25 0,109 T Q4-2 1270 -0.056 0,0965 Then a lineair relation between distance from the DTS desktop computer and slope (a_slope + b_slope*X), and between distance from desktop computer and offset (a_offset + b_offset*X) was derived, resulting in an offset as a function of distance and DTS derived temperatures. Subsequently, this offset was added to the initial DTS derived temperatures. Tcal = T_DTS + ( a_slope + b_slope*X)T_DTS + (a_offset + b_offset*X) with: a_slope :0.085 b_slope :1.78e-005 a_offset:-1.16 b_offset:8.03e-004 In the last step the distance was reversed, with the upstream V-notch weir Q4 at 0 m. Only the part between V-notch weirs Q4 and Q3 (at 565 m) are shown. Measuring instrument: Fibre optic Distributed Temperature Sensor DTS, Maisbich, Luxemburg The fibre optic Distributed Temperature Sensing (DTS) system measures the water temperature along the entire stream. It consists of a dedicated desktop computer with built-in data-acquisition and processing software, to which a fibre optic cable is attached. Short laser pulses (in the order of a few nanoseconds) are sent through the fibre optic cable. When light strikes matter a small portion of the light may be reflected. By measuring the time between the moment the laser pulse is sent through the cable and the moment a reflected photon comes back, the location of reflectance can be determined, since the speed of light in glass is known. The system is from Halo, Sensornet, UK, and has a spatial resolution of 2 m and a temporal resolution of 3 min. This configuration results in a precision of ∼0.1◦C.

校准型光纤分布式温度传感（Distributed Temperature Sensing, DTS）数据集，卢森堡迈斯比奇。父数据集：卢森堡迈斯比奇校准型光纤分布式温度传感（DTS）数据集。
本数据集针对卢森堡迈斯比奇河流域的DTS反演温度的校准流程进行说明。请注意，本次校准仅修正源自DTS设备（英国Sensornet公司Halo型号）的系统偏差，未对光纤电缆未完全浸没于溪流中的时段进行校正。
本次DTS获取的温度数据已通过沿电缆部署的5台独立温度记录仪完成校准，该5台TidbiT v2型温度记录仪（HOBO，美国）分别布设于距DTS主控计算机26、395、931、1111和1270米的位置。需注意，本次研究的河段段落在距主控计算机717米（V型堰Q3）至1282米（V型堰Q4）之间。
每台采样间隔为6分钟的TidbiT记录仪，均基于2008年4月4日至2008年12月4日期间的观测数据，建立了DTS反演温度与TidbiT实测温度和DTS反演温度差值之间的线性关系（dT = a·T_DTS + b）。针对每台记录仪，分别得到了斜率（a）与截距（b）参数如下：
T coolbox：26米，a=-1.31，b=0.0974；
T road：395米，a=-0.49，b=0.0664；
T Mai171u：931米，a=-0.69，b=0.122；
T Mai11u：1111米，a=-0.25，b=0.109；
T Q4-2：1270米，a=-0.056，b=0.0965。
随后，基于距主控计算机的距离与斜率（线性关系为a_slope + b_slope·X）、距主控计算机的距离与截距（线性关系为a_offset + b_offset·X）分别建立线性回归模型，由此得到随距离与DTS反演温度变化的偏差修正量。将该修正量叠加至初始DTS反演温度中，校准后温度计算公式为：
T_cal = T_DTS + (a_slope + b_slope·X)·T_DTS + (a_offset + b_offset·X)
其中参数取值为：a_slope=0.085，b_slope=1.78×10^-5，a_offset=-1.16，b_offset=8.03×10^-4。
最后一步，对距离坐标进行反转，将上游的V型堰Q4设为0米起点。本次仅展示了V型堰Q4与Q3（距起点565米）之间的河段数据。
测量仪器：卢森堡迈斯比奇光纤分布式温度传感（DTS）系统。
光纤分布式温度传感（DTS）系统可沿整条溪流测量水体温度。该系统由搭载专用数据采集与处理软件的主控计算机及连接的光纤电缆组成。系统向光纤电缆发射纳秒级的短激光脉冲，当光线照射到介质时会有少量光被反射。通过测量激光脉冲发射时刻与反射光子返回时刻的时间差，结合玻璃介质中的光速已知值，即可确定反射点的空间位置。本系统为英国Sensornet公司的Halo型号设备，空间分辨率为2米，时间分辨率为3分钟，该配置下的测量精度约为±0.1℃。