Where is the tide measured at Brisbane Bar ?

[fergie]

hi all.

i have a question that might seem a bit strange but does anyone know where the tide leve

for the brisbane bar, is measured from, (so when they say it's a high tide at 2.4mtrs, where is that measured from). someone has asked me this question and i have no idea why they want to know but i thought i would put it out there to see if anyone does know.

[Travis]

Height Reference Datum All elevations within the reference frame are relative to the Lowest Astronomical Tide (LAT). The elevation of this datum was calculated from tidal predictions, in accordance with its definition, in the mid 1980’s. Because the LAT is the navigation chart datum for Australian waters, it will be incorporated into the reference frame at its present elevation.

Thats all i could find, bit of a mouthful but makes sense...

[fergie]

cheers travis

:laugh: :laugh: gonna get a dumb founded look explaining that one :laugh: :laugh:

[Travis]

Print it out and hand it too him :laugh:

[Davo_Dinkum]

i figured Brisbane bar is the mouth of the river.

as with out dredging there would be a bar there .

never thought about it more than that.

[Travis]

Basically measured from the lowest tide prediction posible in aussie waters..

Lowest Astronomical Tide (LAT): The lowest tide level which can be predicted to occur under average meteorological conditions and under any combination of astronomical conditions. Increasingly used as chart datum, for example, for all new Australian charts.

[nadders]

brisbane bar cutting is at the mouth of the river, somwhere in line with the luggage pt outlet and the wharves opposite i think to be very specific, but in practical terms, the mouth of the river

[Travis]

Wasnt the question where do they measure the tide hights written on the tide charts from?

(so when they say it's a high tide at 2.4mtrs, where is that measured from).

[flexo]

hey Fergie this is the only help full info I could find this is a link to all the australian tide guages used by the BOM hope it helps. they must have a way of working it out as for the exact location of the brisbane bar is it not NW of Moreton???

/>http://www.bom.gov.au/oceanography/projects/abslmp/data/index.shtml

[Travis]

So say the LAT is north of darwin somewhere... the tide hights of the brisbane bar are still measured from that location.....

[hooked_on_trout]

I would think there is some kind of height sensor on a buoy somewhere close by?

So if the lowest tide (Lat) was measured at 5 meters depth at the buoy, then everything above that would be tide movement.So if the sensor measured 7.1 meters depth at high tide then that's a 2.1 meter tide.

Just guessing around, because the reference point would also change, because the depth will vary with sand build up and removal over time.

Unless the height is offset from sea level, then you would be measuring fluctuations in height, not the actual depth.

my 2c

Cheers

[justham]

There would be a sensor on the side of the channel markers. When I was diving in Perth we had the job of cleaning them every 6 months or so.