GPS - Sea level rise vs maps

Author

Sea level rise vs maps

Christoph Bouthillier

2007-07-11, 10:33 am

Dear Listeners:

Just out of pure curiosity and not being geographically trained: What will
happen to "sea level" or "Normalnull" or "Amsterdam NAP" etc. when all
today's maps, GPS-es etec. are based on a value that obviously is expected
to rise in the coming years/decennia etc. Will there be something like "Lat
xxx - Lon yyy - WGS84 - sea level as per 1 januari 2000"? By comparison: If
the length of the Parisian meter or the weight of the kilo would change for
whatever reason, all newer measurements based upon those standards would
lose their reference somehow, too / would have to be marked as such.

Just curious;=)

---
Met vriendelijke groet / Mit freundlichen Gruessen / With kind regards
Christoph Bouthillier
p/o\s/t atsign ohnotekstotaaloh nocom
Leave out: \ / oh no
---

Phil Wheeler

2007-07-11, 10:33 am

Christoph Bouthillier wrote:
> Dear Listeners:
>
> Just out of pure curiosity and not being geographically trained: What will
> happen to "sea level" or "Normalnull" or "Amsterdam NAP" etc. when all
> today's maps, GPS-es etec. are based on a value that obviously is expected
> to rise in the coming years/decennia etc. Will there be something like "Lat
> xxx - Lon yyy - WGS84 - sea level as per 1 januari 2000"? By comparison: If
> the length of the Parisian meter or the weight of the kilo would change for
> whatever reason, all newer measurements based upon those standards would
> lose their reference somehow, too / would have to be marked as such.
>

Since the effect is slow, it will be outdpaced by
obsolescence of the GPS hardware itself. In any
case virtually all GPS receivers accept updated
map sets .. either from a computer or (automobile
units) a DVD or a dealer.

Phil

Bernd Nebendahl

2007-07-11, 10:33 am

> By comparison: If
> the length of the Parisian meter or the weight of the kilo would change for
> whatever reason, all newer measurements based upon those standards would
> lose their reference somehow, too / would have to be marked as such.

Just on a side note. That is one of the main reasons, why much effort has been
and is still put into making the units independent of any prototype. In case of
the meeter this has been done quite some time ago by fixing the numerical value
of the velocity of light and defining the second through a certain transition of
an electronic level of a Cs-Atom. In principle, by fixing the weight of a single
silicon atom, one could produce a kilogram without the need of a prototype (grow
a perfect Si single crystal, make a perfect sphere, measure the latice constant
and radius of sphere, from that you know the number of atoms in the sphere and
by multiplying with the fixed mass of a single atom you know the mass of the
sphere. The reason why this has not been done so far, is that there achieved
accuracy did not yet meet their aggesive goals)

Bernd

Christoph Bouthillier

2007-07-11, 12:33 pm

"Bernd Nebendahl" < Bernd_NOSPAM_Nebenda
hl@gmx.de> schrieb im Newsbeitrag
news:4694f07e$0$2099
9$9b4e6d93@newsspool
1.arcor-online.net...
>
> Just on a side note. That is one of the main reasons, why much effort has
> been and is still put into making the units independent of any prototype.
> In case of the meeter this has been done quite some time ago by fixing the
> numerical value of the velocity of light and defining the second through a
> certain transition of an electronic level of a Cs-Atom. In principle, by
> fixing the weight of a single silicon atom, one could produce a kilogram
> without the need of a prototype (grow a perfect Si single crystal, make a
> perfect sphere, measure the latice constant and radius of sphere, from
> that you know the number of atoms in the sphere and by multiplying with
> the fixed mass of a single atom you know the mass of the sphere. The
> reason why this has not been done so far, is that there achieved accuracy
> did not yet meet their aggesive goals)
>
> Bernd
>

Yes, Bernd, I am aware of these efforts and their obstacles. But I wonder
how it could be achieved to define "forever" a/the "null level" in a way
that "sticks" and at the same time is easy to check, understand and
implement, both for paper maps and digital devices. The null level at sea is
so much more fluid (even literally) than a meter or a Cs atom. Meter and
yard sticks are - at least theoretically - the same since their conception
but how on earth can you manage such *creeping* changes? Just a
very simple example: I had to have my house measured by a geodetic engineer
on September 2006. The rooftop was at 600,55 meters above sea level and that
plan is filed at an official office. What is the rooftop in September 2007?
600,51 meters? Imagine another house being built next to it in 2030. Will
the builders who look at that drawing then in 2030 be aware of the x,x
centimeters sea level rise?

---
Met vriendelijke groet / Mit freundlichen Gruessen / With kind regards
Christoph Bouthillier
p/o\s/t atsign ohnotekstotaaloh nocom
Leave out: \ / oh no
---

Christoph Bouthillier

2007-07-11, 12:33 pm

"Phil Wheeler" <wt6uh-ng7@yahoo.com> schrieb im Newsbeitrag
news:4694e406$0$2477
1$4c368faf@roadrunne
r.com...
> Christoph Bouthillier wrote:
>
> Since the effect is slow, it will be outdpaced by obsolescence of the GPS
> hardware itself. In any case virtually all GPS receivers accept updated
> map sets .. either from a computer or (automobile units) a DVD or a
> dealer.
>
> Phil

Hello Phil,

OK, I understand. But then all printed maps will become obsolete, won't
they? And the warden of a mountain hut where you can read "2355 meters above
sea level" (where you normally re-calibrate your GPSr) will have either to
change his sign every 20 years or so, or simply add a sign "Back in 2000 -
and kindly calculate any deviation yourself".

What about architects, geodetic engineers etc. - won't they need to
agree *now* on a certain place at a certain point in time as the ultimate
reference to avoid future problems in communication? (per country)
There was e.g. a deviation of approx. 40 cm in level when they built a
bridge
about 4 years ago on the border between Switzerland and Germany- the
Adriatic being of a different level from the North Sea. The ends didn't meet
of course. I could imagine suchlike problems becoming more
frequent/acute/nasty to manage with
the additional "troublesome factor" of raising sea levels.

---
Met vriendelijke groet / Mit freundlichen Gruessen / With kind regards
Christoph Bouthillier
p/o\s/t atsign ohnotekstotaaloh nocom
Leave out: \ / oh no
---

Dominic Sexton

2007-07-11, 12:33 pm

In message < 5515d$4694fe99$d4ba0
6cf$25506@news.speedlinq.nl>, Christoph
Bouthillier <post@tekstotaal.com> writes
> Just a
>very simple example: I had to have my house measured by a geodetic engineer
>on September 2006. The rooftop was at 600,55 meters above sea level and that
>plan is filed at an official office. What is the rooftop in September 2007?
>600,51 meters? Imagine another house being built next to it in 2030. Will
>the builders who look at that drawing then in 2030 be aware of the x,x
>centimeters sea level rise?

There will be no change unless the Dutch government's mapping agency
decides to produce a new vertical datum. If they do I am sure that they
will also let people know the offset between the old and the new.

The vertical datum will be referred to as mean sea level but that is in
reference the mean sea level as determined with a tidal gauge from which
readings were taken over several years. It will have equated to the mean
sea level at that point over that time span. It may not equate well to
measurements at a different point or time.

Once determined the mean sea level will have been fixed as the vertical
datum therefore it doesn't matter now if the actual mean sea level has
changed the heights will still be referred to the vertical datum fixed
from the prior readings.

Therefore unless the land mass under your house has moved vertically
when compared to the vertical datum point the height of the rooftop will
be the same despite any change in the actual mean sea level since it was
measured.
--
Dominic Sexton

Stichting ST

2007-07-12, 4:33 am

On Wed, 11 Jul 2007 18:00:26 +0200, "Christoph Bouthillier"
<post@tekstotaal.com> wrote:

>
>
>"Phil Wheeler" <wt6uh-ng7@yahoo.com> schrieb im Newsbeitrag
> news:4694e406$0$2477
1$4c368faf@roadrunne
r.com...
>
>Hello Phil,
>
>OK, I understand. But then all printed maps will become obsolete, won't
>they? And the warden of a mountain hut where you can read "2355 meters above
>sea level" (where you normally re-calibrate your GPSr) will have either to
>change his sign every 20 years or so, or simply add a sign "Back in 2000 -
>and kindly calculate any deviation yourself".
>
>What about architects, geodetic engineers etc. - won't they need to
>agree *now* on a certain place at a certain point in time as the ultimate
>reference to avoid future problems in communication? (per country)
>There was e.g. a deviation of approx. 40 cm in level when they built a
>bridge
>about 4 years ago on the border between Switzerland and Germany- the
>Adriatic being of a different level from the North Sea. The ends didn't meet
>of course. I could imagine suchlike problems becoming more
>frequent/acute/nasty to manage with
>the additional "troublesome factor" of raising sea levels.
>
About the bridges that went wrong I heard the story as followes:
they exactly know that there was a difference between the hight coming from
Switzerland and the one coming from Germany.
Things went wrong with communications.
Who takes care of the difference? The Swiss. And very precise they did it
(Swiss quality work). Unto the millimeter!
But they had the sign wrong. So instead of 24 cm in the good direction they
went in the wrong direction and ended up with a 2x24 cm. difference.

Piet

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