Description of Files porta40.txt, porta41.txt and porta42.txt
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These files are digitised versions of sea level data collected by Thomas
Lempriere at Port Arthur, Tasmania, Australia. They cover the period
1840 to 1842, but are incomplete for 1840. The originals are in hardcopy 
form at the following locations:

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porta40.txt
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Sea level data for 1840, from:

  P2472/Item 9

at:

  National Archives of Australia, 
  Hobart Office,
  85 Macquarie Street, 
  Hobart,
  Tasmania 7000,
  Australia.

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porta41.txt and porta42.txt
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Sea level data for 1841 and 1842, from:

  MA59

at:

  Royal Society Archives,
  The Royal Society,
  6-9 Carlton House Terrace, 
  London SW1Y 5AG,
  United Kingdom.

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Correction of some obvious errors in the original hardcopy data was 
performed during this digitisation, which was carried out by Dr. David 
Pugh, presently Chairperson, Intergovernmental Oceanographic Commission 
of UNESCO (IOC).

The exact location of the observations is unknown, but is almost certainly 
within 1 km of 43 deg 08 min 50 secs South, 147 deg 51 min 10 sec East.

Details of the tide gauge have not survived.

The datum of these sea levels is 1474.2 mm BELOW AHD (Tasmania).

For information on local survey marks, see:

  Watson, C.S., 1999. A Contribution to Absolute Sea Level in 
    Tasmania, B. Surv. (Hons.) thesis, 200 pp., University of 
    Tasmania, Hobart, Tasmania, Australia.

Further details of the historic documents and an analysis of the data 
contained in them are given by:

  Pugh, D., Hunter, J., Coleman, R. and Watson, C., 2002. A comparison of
    historical and recent sea level measurements at Port Arthur, Tasmania,
    International Hydrographic Review, Vol. 3, No. 3 (New Series), 27-46,

and:

  Hunter, J., Coleman, R. and Pugh, D., 2003. The sea level at Port Arthur,
    Tasmania, from 1841 to the present, Geophysical Research Letters, 
    Vol. 30, No. 7, 54-1 to 54-4, doi:10.1029/2002GL016813.

Data Format
***********

Each day consists of 4 lines:

MM DD  hhmmffii     ddd
       hhmmffii     ddd
       hhmmffii     ddd
       hhmmffii     ddd

where:

  MM is the month number,
  DD is the day number of the month,
  hh is the hour of the day (24-hour clock),
  mm is the minute of the hour,
  ffii is the sea level in feet ("ff") and inches ("ii"), and
  ddd is the time difference in minutes between this and the previous line
      ("ddd" was used for diagnostic purposes).

The time zone is believed to be Hobart local time, or UTC + 9 hours 49 minutes.
For a discussion of the probable time zone, see:

  Hamon, B., 1985. Early mean sea levels and tides in Tasmania, Search, 
    Vol. 16, No. 9-12, 274-277.

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For further information, contact:

John Hunter,
Antarctic Climate & Ecosystems Cooperative Research Centre,
Private Bag 80,
Hobart,
Tasmania 7001,
Australia

email: john.hunter@utas.edu.au
phone: +61 3 6226 7849

John Hunter, 20 April 2006

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