Calibrated DTS data, Maisbich, 2008-11

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.

校准后的光纤分布式温度传感（Distributed Temperature Sensing, DTS）数据，卢森堡迈斯比奇河

父数据集：校准后的光纤分布式温度传感（DTS）数据，卢森堡迈斯比奇河

## 校准流程说明
本数据集针对卢森堡迈斯比奇河的DTS反演温度进行校准流程说明。本次校准仅修正来自英国Sensornet公司Halo型DTS设备本身的系统偏差，未修正线缆未完全浸没于溪流中的时段所产生的误差。

本次校准共使用5台独立温度记录仪（TidbiT v2型温度记录仪，美国HOBO公司），其安装位置分别距离DTS主控计算机26 m、395 m、931 m、1111 m和1270 m。本次研究的支流段位于距主控计算机717 m（V形堰Q3）至1282 m（V形堰Q4）之间。

针对每台以6分钟间隔采集数据的TidbiT记录仪，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反演温度的差值」之间的线性关系：`dT = a*T_DTS + b`，并得到每个测点对应的斜率`a`与截距`b`，各测点参数如下：
T coolbox（26 m）：斜率a=-1.31，截距b=0.0974；
T road（395 m）：斜率a=-0.49，截距b=0.0664；
T Mai171u（931 m）：斜率a=-0.69，截距b=0.122；
T Mai11u（1111 m）：斜率a=-0.25，截距b=0.109；
T Q4-2（1270 m）：斜率a=-0.056，截距b=0.0965。

随后分别建立「距离主控计算机的距离」与斜率、截距的线性关系：斜率为`a_slope + b_slope*X`，截距为`a_offset + b_offset*X`，由此得到温度偏差随距离与DTS反演温度的函数关系。最终将该偏差值加入初始DTS反演温度，得到校准后温度的计算公式：
`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`

本次校准的最后一步为距离反转，将上游的V形堰Q4设为0 m起点，最终仅展示V形堰Q4与Q3（距起点565 m）之间的溪流区段。

## 测量仪器说明
光纤分布式温度传感（DTS）系统，卢森堡迈斯比奇河。
该系统可沿溪流全程测量水体温度，由搭载内置数据采集与处理软件的专用主控计算机及连接的光纤线缆组成。系统向光纤线缆发送纳秒级短激光脉冲，当光线照射到物质时会产生少量反射；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，结合玻璃中光速已知的特性，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 m，时间分辨率为3 min，测量精度约为0.1℃。