Davis Tide Gauge Data 1993-2017

Over time there have been a number of tide gauges deployed at Davis Station, Antarctica. The data download files contain further information about the gauges, but some of the information has been summarised here. Note that this metadata record only describes tide gauge data from 1993 to 2017. More recent data are described elsewhere.Tide Gauge 3 (TG003)This folder contains the following folders:-early_tg_files     monthly_tg_files    monthly download files from the submerged tide gauge at Davis deployed in March 1993.    These files are ASCII hexadecimal files. They need to be converted to decimal.    The resultant values are absolute seawater pressures in mbar.        Remaining files are downloaded in normal format obtained directly from tide gauge.    raw    memory images from submerged tide gauge. file extension is memory bank number.     These files are processed by a utility called tgxtract.exe which creates files in same format as those in old_tidedata folder.    These file have extension .srt. They are then converted to decimal pressure values.output    output file (.srt) which have been sent to BoM.Tide Gauge 6 (TG006)This folder contains the following folders:-raw    memory images from submerged tide gauge. file extension is memory bank number.     These files are processed by a utility called tgxtract.exe which creates files in same format as original download format.    These file have extension .srt.     These files are ASCII hexadecimal files. They need to be converted to decimal.    The resultant values are absolute seawater pressures in mbar.output    output file (.srt) which have been sent to BoM.Tide Gauge 12 (TG012) and Tide Gauge 12i (TG012i)Documentation notes from the older metadata records:Documentation dated 2001-03-07Davis Submerged Tide Gauge The gauge used at Davis was designed in 1991/2 by Platypus Engineering, Hobart, Tasmania . It was intended to be submerged in about 7 metres of water in a purpose made concrete mooring in the shape of a truncated pyramid. The gauge measures pressure using a Paroscientific Digiquartz Pressure Transducer with a full scale pressure of 30 psi absolute. The accuracy of the transducer is 1 in 10,000 of full scale over the calibrated temperature. The overall accuracy of the system is better than +/- 3 mm for a known water density. Data is retrieved from the gauges by lowering a coil assembly on the end of a cable over a projecting knob on the top of the gauge and by use of an interface unit, a serial connection can be established to the gauge. Time setting and data retrieval can be then achieved. One of these of these gauges was deployed at Davis in early 1993 in a mooring in ???? bay. Data has been retrieved from these gauges irregularly since then. The records are complete since deployment except for a few days in late 1995. The loss was caused by a fault in the software which allows directory entries to overwrites data when the directory memory has been filled. Conversion of raw data to tidal records is done as detailed in document DATAFORMAT1.DOC . As the current gauge is expected to require a new battery soon, a new mooring has been placed close to the original. A new gauge is at Davis ready to be deployed as time permits.LevellingLevelling of the gauge at Davis was done by installing a temporary pressure type gauge in shallow water and recording sealevel for 10 days. The temporary gauge was precisely levelled to a permanent benchmark. The temporary gauge was then calibrated using a known height of seawater from the bay at the same temperature as the water in the bay. The density of the seawater was accurately measured. This work, in conjunction with the tidal records from the submerged gauge have enabled a MSL for Davis to be established. Permanent Tide Gauge. No suitable sites for an Aquatrak type gauge at Davis have been identified.Documentation dated 2008-10-17There are two submerged tide gauges at Davis. One is soon to be removed to have its battery replaced.These gauges record pressure and temperature values. The download software only formats these records to produce 10 minute average presure values (hPa) and unscaled temperature values.

随着时间推移，南极戴维斯站（Davis Station）已部署多台潮位仪（tide gauge）。数据下载文件包含潮位仪的更多详细信息，但此处已对部分信息进行了汇总。请注意，本元数据记录仅涵盖1993年至2017年的潮位仪数据，近期数据的相关说明见于其他文档。

### 潮位仪3（Tide Gauge 003, TG003）
本文件夹包含以下子目录：
- `early_tg_files`与`monthly_tg_files`：1993年3月部署于戴维斯站的水下潮位仪（submerged tide gauge）的月度下载文件。此类文件为ASCII十六进制格式，需转换为十进制格式，转换后得到的数值为以毫巴（mbar）为单位的绝对海水压力。
- 其余文件为直接从潮位仪获取的常规格式数据：
- `raw`：水下潮位仪的内存镜像文件，文件扩展名为内存bank编号。此类文件需通过名为`tgxtract.exe`的工具程序进行处理，该工具将生成与`old_tidedata`目录格式一致的文件，扩展名为`.srt`，后续需将其转换为十进制压力数值。
- `output`：已发送至BoM的`.srt`格式输出文件。

### 潮位仪6（Tide Gauge 006, TG006）
本文件夹包含以下子目录：
- `raw`：水下潮位仪的内存镜像文件，文件扩展名为内存bank编号。此类文件需通过名为`tgxtract.exe`的工具程序进行处理，该工具将生成与原始下载格式一致的文件，扩展名为`.srt`。此类文件为ASCII十六进制格式，需转换为十进制格式，转换后得到的数值为以毫巴（mbar）为单位的绝对海水压力。
- `output`：已发送至BoM的`.srt`格式输出文件。

### 潮位仪12（TG012）与潮位仪12i（TG012i）
#### 旧元数据记录文档说明
1. **2001年3月7日文档**
戴维斯站水下潮位仪：该潮位仪由塔斯马尼亚州霍巴特的Platypus Engineering公司于1991/1992年设计，计划部署于约7米水深的定制混凝土锚泊系统中，锚泊系统外形为截头棱锥。潮位仪采用Paroscientific Digiquartz压力传感器（Paroscientific Digiquartz Pressure Transducer）进行压力测量，满量程绝对压力为30 psi。该传感器在标定温度范围内的精度为满量程的1/10000；在已知海水密度的前提下，整套系统的整体精度优于±3毫米。
数据可通过以下方式获取：将线缆末端的线圈组件下放至潮位仪顶部的突出旋钮处，通过接口单元建立串行连接，即可完成时间校准与数据获取。1993年初，此类潮位仪中的一台被部署于戴维斯站某海湾的锚泊系统中（原文标注为`???? bay`）。自部署以来，数据获取工作并不规律，除1995年末的数天外，所有记录均完整。此次数据丢失源于软件故障：当目录内存已满时，目录条目会覆盖数据。
原始数据至潮汐记录的转换流程详见文档`DATAFORMAT1.DOC`。由于当前潮位仪的电池即将耗尽，已在原锚泊系统附近布置了新的锚泊装置，待时机成熟即可安装新的潮位仪。

#### 水准测量
戴维斯站潮位仪的水准测量工作通过以下方式完成：在浅水区安装临时压力式潮位仪，连续10天记录海平面高度。将临时潮位仪与永久基准点进行精确水准联测，随后采用与海湾水温一致的已知海水高度对临时潮位仪进行标定，并精确测量海水密度。结合上述工作与水下潮位仪的潮汐记录，已确定戴维斯站的平均海平面（Mean Sea Level, MSL）。

#### 永久潮位仪
戴维斯站未找到适合安装Aquatrak型潮位仪的场地。

2. **2008年10月17日文档**
戴维斯站现有两台水下潮位仪，其中一台即将被送回更换电池。此类潮位仪可记录压力与温度数据，下载软件仅支持将记录格式化为10分钟平均压力值（单位：百帕（hPa））与未缩放的温度值。