¨
¨ "The YoYoMan" escribió en el mensaje
¨ ...
¨
¨ Ep!
¨
¨ where is the zero point of "sea level" (gps coordinates) ????
¨
¨ in what sea/ocean ????
¨
¨ in what point ???
¨ I think the reference is not a point but a surface, the geoid surface, which
¨ is an oblate spheroid that is determined I think by measuring the gravity (I
¨ don't know how, thpough). This gives 0 meter altitude.
¨
¨
¨ how is measured altitude of mountains ?
¨
¨ how mach meters have the Gaorisankar (Everest) ???
¨ some people say 8.848 others 8.850... what is correct ???
¨
¨ Actually the Chinese are just sending a mission to determine the new height
¨ of the Everest, since it is believed that Everest snow cap is melting down
¨ due to global warming.

what ? :-) snow are a thing variable!!! stupid people not insert a bar of metal
in snow for found the real top of rock ? oooooh my god!!!

¨ Dead sea is at "sea level" ???
¨ Dead sea is approx 400m below sea level.
¨ http://ask.yahoo.com/ask/20010920.html

a sea and his "sea level" are under "sea level" ???? very crazy no ?

¨ the big depression in water surface in Indic ocean of -300m. is also at
¨ "sea
¨ level" ??
¨
¨ I didn't know that. Where did you find that ?

in book:
1001 things everyone should know about science
by james trefil

¨ after indic tsunami and global changes in planet "sea level" also sufer
¨ variations ???
¨ Actually, parts of sumatra shore ahev dived under water, beacuse the
¨ earthquake have lowered part of the island. The variation of sea level was
¨ but transient, as far as I know.

after gibraltar terra connection with africa break the sea level of all
mediterranian coast make a big elevation... if a wall are builded another time
betheen africa and al-andalus the "sea level" of mediterranean sea return to his
original level... and many cities and constructions rising...

¨ a reveure des Catalunya, the YoYoMan :-)
¨
¨
¨ Doncs si home, a reveure ! Que vagi be a Catalunya ! Coneixes-tu foros de
¨ geología en castellá o en catalá ? En vaig buscar pero no vaig trobar rés.
¨
llistes en catala:
La Teranyina - Samizdat. Llistes de correu dels Països Catalans
http://www.teranyina.net/samizdat.html
tambe potser trobes quelcom a : www.rescat.net/
a l'institut cartografic de catalunya: www.icc.es

dona un cop d'ull a les llistes de www.rediris.es i no t'estranys que encara
aquests paios escriguin amb ploma natural, potet de tinta i suca que sucaras :-)

per cert has mirat la ESRA o ESNA la base de dades en 3-d de la nasa de la terra
de la zona dels pirineus ?

fins aviat i que vagui be pel canada! :-)

"Wally" wrote in message
k...
"Gilligan" wrote in message
news:uoeLd.2473

Yo,

Yo man.

He's a cellist, isn't he?

Yeah, yeah ....man!



Regards


Donal
--

Sealevel is way over my head...



Cheers!


Remco --- Dutch

"« Paul »" wrote in message
...
JG wrote:

No. Global warming is not Bu****'s fault. He's just making it worse.

Are you saying that Bush is causing the increase in
solar energy output?

All that hot air coming out of his mouth, don't you know...

"Wally" wrote in message
k...
"Gilligan" wrote in message
news:uoeLd.2473

Yo,

Yo man.

He's a cellist, isn't he?


I thought he was a rapper.

Rod Burns wrote in sci.geo.geology:

I think the reference is not a point but a surface, the geoid surface,
which is an oblate spheroid that is determined I think by measuring
the gravity (I don't know how, thpough). This gives 0 meter altitude.


Very close. The ellipsoid is a mathematical reference surface used by
geodesists and cartographers. There are several, but GRS80 or WGS84 are
most commonly used today.

The geoid is a gravitational equipotential surface undulating above and
below the ellipsoid. The WGS84 value for the gravitational potential was
chosen for best fit to the global sea surface, but it doesn't follow the
sea surface. [In fact "the geoid" is a misnomer, since there are actually
several different potentials that have merit.]

Mean sea level is location dependent and may vary from the geoid due to
ocean dynamics. Different datums specify mean sea level by averaging
designated tide guages.

Elevation is measured with reference to a datum.

--
Jim Irwin
http://www.holoscenes.com

jimirwin a écrit dans le message ...
Rod Burns wrote in sci.geo.geology:

I think the reference is not a point but a surface, the geoid surface,
which is an oblate spheroid that is determined I think by measuring
the gravity (I don't know how, thpough). This gives 0 meter altitude.


Very close. The ellipsoid is a mathematical reference surface used by
geodesists and cartographers. There are several, but GRS80 or WGS84 are
most commonly used today.

The geoid is a gravitational equipotential surface undulating above and
below the ellipsoid. The WGS84 value for the gravitational potential was
chosen for best fit to the global sea surface, but it doesn't follow the
sea surface. [In fact "the geoid" is a misnomer, since there are actually
several different potentials that have merit.]

Mean sea level is location dependent and may vary from the geoid due to
ocean dynamics. Different datums specify mean sea level by averaging
designated tide guages.

Elevation is measured with reference to a datum.

--
Jim Irwin
http://www.holoscenes.com


mean sea level -A tidal datum: the arithmetic mean of hourly water
elevations observed over a specific 19-year cycle. Points on land can be
referenced to a mean sea level, in which case the datum assumes zero
elevation.

" sea level is not a simple surface. Since the sea surface conforms to the
earth's gravitational field, MSL also has slight hills and valleys that are
similar to the land surface but much smoother. However, zero elevation as
defined by Spain is not the same zero elevation defined by Canada, which is
why locally defined vertical datums differ from each other."

The geoid corresponds to mean sea level.
In land covered areas, the geoid is the surface that would be determined by
the level to which water would rise in narrow canals cut through the
continents.

JOL

maison.mousse wrote in sci.geo.geology:

Since the sea surface conforms to the
earth's gravitational field, MSL also has slight hills and valleys
that are similar to the land surface but much smoother.

Yes, the mean sea surface (a.k.a. mean ocean topography) conforms to the
gravitational potential surface to within about 1 meter. Ocean topography
is also affected by long term conditions such as prevailing winds,
currents, temperature, and salinity -- factors in addition to the
gravitational field. The Geoid is defined by the gravitational field
alone.

There are efforts to quantify the differences more accurately.

--
Jim Irwin
http://www.holoscenes.com