Tide Gauge Records 1996-1997, Beaver Lake, Australian Antarctic Territory

Brief description

Tides were measured using a portable pressure transducer secured to fast ice at the mouth of Pagodroma Gorge with the transducer about 4 metres below low water line. A 30 day record was obtained.

Documentation dated 2001-03-07
Beaver Lake and the Stillwell Hills

In Dec 1996 - Jan 1997 a temporary pressure type tide gauge was deployed at Beaver Lake and the Stillwell Hills in open water.
Timed water level measurements were made over this period.
From these data a value for MSL was found for Beaver Lake and the Stillwell Hills.

Lineage

Progress Code: completed

Statement: The data set between the time of deployment and recovery is complete. The dataset is complete except for a few days of records in late 1996. The portable gauge was deployed for 30 days and when recovered the data were downloaded and processed. These records and the leveling records were sent to the National Tidal Unit where a value for mean sea level was derived. Tidal records are checked for gross errors in height values and obvious timing errors. Further checks are done by NTU during processing.

As of 2016-03-03 - these data are currently being reworked at the Australian Antarctic Division to improve the quality of the dataset.

Processing of data from Macquarie Island, Beaver Lake, Stillwell Hills and Heard Island Tide Gauges.

There have been two type of dataloggers used at Macquarie Island, Beaver Lake, Stillwell Hills and Heard Island.

Vitel

These units were used when the gauge was first commissioned mainly because they were designed to interface with the Bartex controller used with the Aquatrak Sensor. There were several small problems with these units. The Aquatrak records could not have access to the full memory so the loggers had to be downloaded every 23 days. Each line of the ASCII records obtained were padded to 80 characters making a 23 day record extremely large. An alternative method involving downloading the entire memory had the disadvantage that the records had to be extracted from a binary file and the whole memory had to be downloaded.

A further problem was that logging ceased while data was downloaded. This resulted in the loss of several records every download.

The Vitel datalogger did not included interface circuitry for a pressure transducer or thermistors. This had to be provided separately.


Platypus Engineering Dataloggers.

These were designed specifically for this application.

They had the following features.

Interface circuitry for all the sensors was built into the logger.

Flash memory was used for data security. The flash memory also allowed the unit to be reprogrammed via the serial port

Up to 1 Mbyte of memory was provided.

The logger was built into a waterproof box.

A scheduled wake up feature was included to allow the logger to wake up a sleeping radio modem at a predetermined time each day.


Data Processing

The data processing required was as follows.

Vitel ASCII downloads.

Data were sent in form downloaded to NTF. Some later files had the padding spaces removed to produce a smaller file.

Vitel Binary files.

Data were extracted from the binary memory dumps with a utility called XLATE which produced a verbose ASCII file. Data from both the Druck and Aquatrak sensors were assembled into a composite file before sending to NTF.


Platypus Engineering Logger files.

The downloads from these loggers is in a hex format. The file names have the extension .RAW. These files are processed with a utility called READLOG to produce a time series. The output files called ..LOG , were further processed to correct a bug in READLOG and to convert Druck pressure readings into water height units.

The program to do this is called AQUACALC or DRCALC.

These utilities will be written into the one conversion program.

To convert pressure units to height, an assumed value of SG of 1.028 is used.

The last thermistors fitted to the Aquatrak installation were calibrated in the laboratory and calibration coefficients derived.