French map datum?

Jeremy Harris - SUN IMP Slough

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Jan 22, 1997, 3:00:00 AM1/22/97

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Anyone know what datum the (excellent) Michelin "yellow" series of
maps is based on? I can't find it anywhere round the edges.

Cheers,
Jeremy

NB anti-automail in from address

Berthold Pasch

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Jan 27, 1997, 3:00:00 AM1/27/97

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In article <5c4qkn$j...@flonk.uk.sun.com>,

j...@redford.uk.sun.com.antispam (Jeremy Harris - SUN IMP Slough) wrote:
>Anyone know what datum the (excellent) Michelin "yellow" series of
>maps is based on? I can't find it anywhere round the edges.
>
>Cheers,
> Jeremy

Don't the French use a completely different coordinate system?
With 400 degrees instead of 360, and Paris (I think Notre Dame) as the
point where the zero degree longitude runs through.
I have seen these coordinates on any French map that I got a hold of
so far (mostly Michelin 1:200000 road maps, and the 1:100000 topo
maps that are common in France).
I don't know what map datum (i.e. WGS84 or other) they use. If this is
of any relevance at all with regard to their degree system.

With best regards, Berthold Pasch

Heinrich Pfeifer

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Jan 29, 1997, 3:00:00 AM1/29/97

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In article <dMQ7yETb...@rhein-neckar.netsurf.de>,
bpa...@rhein-neckar.netsurf.de says...

>Don't the French use a completely different coordinate system?
>With 400 degrees instead of 360, and Paris (I think Notre Dame) as the
>point where the zero degree longitude runs through.
>I have seen these coordinates on any French map that I got a hold of
>so far (mostly Michelin 1:200000 road maps, and the 1:100000 topo
>maps that are common in France).
>I don't know what map datum (i.e. WGS84 or other) they use. If this is
>of any relevance at all with regard to their degree system.
>
>With best regards, Berthold Pasch

At least for the 1:50000 and 1:25000 topo maps of i.g.n (institute
geographique national), they use the map datum n.t.f (nouvelle triangulation
francaise) with lambert projection, and European 1950 for UTM and degrees.

Yes, on some french maps they use a 400 degrees system, indicated as "gr"
instead of "°". In this case, the origin longitude is Paris, Pantheon. This
is 2°20'14.025" East of Greenwich.

Have a look at
http://habicht.bauv.unibw-muenchen.de/voser/bezug/datum_lib_txt.html
for the parameters of n.t.f. and other details.

Best regards - Heinrich Pfeifer

Jeremy Harris - SUN IMP Slough

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Feb 3, 1997, 3:00:00 AM2/3/97

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Just to follow up on my original query, I've now found Michelin yellow
maps with both degree and grad grids. The grad ones might be older, I'm
not sure.

Cheers,
Jeremy

Margaret Stedman

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Feb 3, 1997, 3:00:00 AM2/3/97

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In article <5d4e2a$k...@flonk.uk.sun.com>, j...@redford.uk.sun.com.antispam
says...

Hi Jeremy,

I bought a complete set of the Michelin "yellow" maps about 20 years ago,
and was puzzled about the datum after I got a GPS a few months ago. They
are in grads, I am now sure. I too have noticed that the yellows on sale
now seem to have normal degrees. Thanks for your query.

I guess that a general point that arises is that as GPS becomes a
consumer product, publishers of all types of maps must cater for users
who want an absolute location, not just a reference from the index.

Margaret Stedman

Boyd Roberts

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Feb 4, 1997, 3:00:00 AM2/4/97

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The Institut Géographique National [http://www.ign.fr/] maps have UTM.

--
Boyd Roberts <bo...@france3.fr> N 31 447109 5411310

``Not only is UNIX dead, but it's starting to smell really bad.'' -- rob