Calibrated DTS data, Maisbich, 2008-10

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: TidbitDistance(m)ab T coolbox26-1.310,0974 T road395-0.490,0664 T Mai171u931-0.690,122 T Mai11u1111-0.250,109 T Q4-21270-0.0560,0965 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.

经过校准的光纤分布式温度传感（Distributed Temperature Sensing, DTS）数据，卢森堡迈斯比奇（Maisbich）流域
父数据集：卢森堡迈斯比奇流域光纤分布式温度传感校准数据
本数据集针对卢森堡迈斯比奇溪流的DTS反演温度校准流程进行说明。需注意，本次校准仅修正源自英国Sensornet公司Halo型DTS设备本身的系统偏移，未对光缆未完全浸没于溪流中的时段进行校正。
本次校准采用5台独立布置的温度记录仪（TidbiT v2温度记录仪，HOBO，美国），分别位于距离DTS台式计算机26、395、931、1111和1270米的光缆沿线。本次研究的河段范围为距离台式计算机717米（V型堰Q3）至1282米（V型堰Q4）之间的河段。
每台Tidbit记录仪以6分钟为间隔采集数据，在2008年4月4日至2008年12月4日期间，建立了DTS反演温度与Tidbit实测温度和DTS反演温度差值的线性关系：$dT = a cdot T_{DTS} + b$。针对每个测点，得到的斜率($a$)与偏移量($b$)如下：T coolbox26（距26米）：$a=-1.31$，$b=0.0974$；T road395（距395米）：$a=-0.49$，$b=0.0664$；T Mai171u931（距931米）：$a=-0.69$，$b=0.122$；T Mai11u1111（距1111米）：$a=-0.25$，$b=0.109$；T Q4-21270（距1270米）：$a=-0.056$，$b=0.0965$。
随后，建立距离DTS台式计算机的距离与斜率、距离与偏移量的线性关系，分别为$斜率 = a_{slope} + b_{slope} cdot X$、$偏移量 = a_{offset} + b_{offset} cdot X$，最终得到以距离和DTS原始反演温度为变量的偏移量计算公式。将该偏移量添加至初始DTS反演温度中，得到校准后温度：$T_{cal} = T_{DTS} + (a_{slope} + b_{slope} cdot X) cdot T_{DTS} + (a_{offset} + b_{offset} cdot X)$，其中各参数取值为：$a_{slope}=0.085$，$b_{slope}=1.78 imes 10^{-5}$，$a_{offset}=-1.16$，$b_{offset}=8.03 imes 10^{-4}$。
最后，将距离坐标反转，以上游V型堰Q4作为0米起点，本次数据集仅展示V型堰Q4与Q3（间距565米）之间的河段数据。

测量仪器：光纤分布式温度传感器（DTS），卢森堡迈斯比奇流域
该光纤DTS系统可沿整条溪流采集水体温度，系统由内置数据采集与处理软件的专用台式计算机及连接的光缆组成。向光缆发射纳秒级短激光脉冲，当光线照射到介质时会产生少量反射光，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，结合玻璃中光速已知的前提，可确定反射点的空间位置。本系统采用英国Sensornet公司的Halo型设备，空间分辨率为2米，时间分辨率为3分钟，测量精度约为0.1℃。