[OSRS-PROJ] gauss-krueger/transverse mercator

[The MapRef Collection]

"Gerald I. Evenden" wrote:

> In some instances, I have heard that GK (Gauss_Kruger) only applied to
> 5 zones centered on 3E, 9E, 15E, ... ---European coverage.  Regarding
> the German grid you mentioned, it seems strange to use 500,000m easting
> when the zones are only 3 degrees wide, half the GK/UTM width.

This is not correct.
GK may be mathematically treated the same as UTM using for both the transverse mercator formulae.

   * UTM has a scale factor of 0.9996 and zone width of 6°
   * GK therefor has a scale factor of 1.0000 and implementations with 3° Zones (Germany, Austria,
     Easter-Germany, Kroatia, Russia...), but there exist als 6° Zones eg. also in Russia etc, (china has
     zones for 1.5°3°,6°width ...)
   * GK sometimes only is used for the projection type of transverse mercator, but with varying scale,
     zone width ... (e.g gauss-boaga in Italy (scals similar to utm, australia (s=0.99994, zone=2°)

the easting of 500'000m is established for UTM as well as for GK (to avoid negative numbers and to be
symmetrically beyond the central meridian.

for UTM, sometimes you find the zone number previously attached to eastings, but often, an own field for
the zone is found for this information.

the zone description for the eastings in GK varies from country to country and may not be included. the
inclusion gives problem due to the numerical Resolution of real numbers ...
the false northing also may vary from country to country ..
china: 0M northern hemisphere, 10000000 southern hemisphere
australia: 5000000m
and so on.
...
Many of these definitions may also be found at http://www.geocities.com/mapref/mapref.html

>
> Any reading where the easting exceed 500,000m is obviously seriously
> in error and/or the wrong zone (CM) was specified.  Same if the easting
> is negative.
>
> Incidentally, are you capable of specifying the zone number to the Garmin?
> Seems to me that would be required especially when you are on the seam
> between zones and can use either.
>
> As for southern latitudes and GK, I have never heard, but I would think
> that 10,000,000m false northing would apply.  If it is labelled as a German
> system, then southern latitudes don't apply so why bother with a false
> northing.
>
> A trouble with the Gauss-Kruger nomenclature is that it means two
> different things:
> 1) a method of computing the transverse Mercator projection
> 2) a coordinate system identical to UTM except for zone numbering
>
> >From your description of the "German" grid system, this is not
> the same as GK.
> __________________________________________________
> Jerry Evenden and the Low Riders, Katie and  Daisy May
> gevenden at capecod.net  http://www.capecod.net/~gevenden
> ----- Original Message -----
> From: Andreas Lange <Andreas.Lange at Rhein-Main.de>
> To: <osrs-proj at remotesensing.org>
> Sent: Monday, June 12, 2000 7:43 AM
> Subject: [OSRS-PROJ] gauss-krueger/transverse mercator
>
> > Hi,
> >
> > i have a problem with the transverse mercator projection (Gauss-Kruger
> > Projection) only indirectly connected to proj4.
> >
> > I am writing a program for data exchange with garmin gps receivers,
> > which give the position always in lat/lon wgs84, even if the receiver
> > itself displays position and waypoints in 'german grid' coordinates
> > (transverse mercator projection). I know that german grid here for
> > germany uses 3 degree wide meridian stripes (0d, 3d E, 6d E etc.), adds
> > a false easting of 500000 and prefixes the zone (0, 1, 2, 3, etc).
> >
> > But what on the southern hemisphere? Is there a constant false northing
> > of 10000 m added as with UTM? The receiver displays only "----", so that
> > i assume it is not defined for southern hemisphere.
> >
> > What with western longitudes? What with two-digit zones?
> >
> > The receiver gives me the following readings:
> > lat    lon     easting/northing
> > 29.27N 10.5W   5436500/5815100 (??)
> > 29.27N 10.5E   4354200/3240000 (ok)
> > 29.27N 18.83E  5579200/1675000 (??)
> > 29.27N 18.83W  5923300/9718000 (??)
> > 85.44N 18.83E  5009100/0035000 (??)
> > 85.44N 18.83W  5923000/9718000 (??)
> >
> > Are those values (??) only an internal overflow of the receiver?
> >
> > Thank you in advance for any hints,
> >
> > Andreas Lange
> >
> > --
> > Andreas Lange, 65187 Wiesbaden, Germany, Tel. +49 611 807850
> > Andreas.Lange at Rhein-Main.de, A.C.Lange at GMX.net

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