MI Palestine Belt Transverse Mercator

[Cliff Mugnier - University of New Orleans]

John,

The Palestine Belt replaced the Palestine Grid (1928-1942), which was based on
the Cassini-Soldner projection.

The Palestine TM Belt is a Gauss-Kruger TM where the C.M.= 35*12'43.49" East of
Greenwich, Scale Factor at Origin is unity, False Northing Latitude @ Origin =
31*44'02.7490" North, the False Easting is 170251.555 meters, and the False
Norting is 126867.909 meters.

The Clark 1880 used for the Palestine Datum of 1928 is where a = 6,378,300.782
meters, and first eccentricity squared = 0.00680348101782.  Note that there are
several versions of the Clark 1880, the Palestine version is different than the
one used say, in Africa.

The European Datum 1950 is commonly used in the area also, and note that the
first geodetic surveys in the Palestine were done by the military surveyors of
Napoleon Bonaparte  Remember reading about when Napoleon conquered Egypt? 
Well, he did a bit of sight-seeing while on the trip of conquests ...

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

Voice and Facsimile: (504) 280-7095
---
John wrote:
> 
> Cliff,
> I was wondering what information you might have on the 1000 metre Palestine
> Belt grid, Clarke 1880 spheroid. I can find data on the Palestine 1928 datum, > but 
>nothing on the Palestine Belt projection. 
> I don't know what projection system was used, or
> what the constants are. There is a gentleman in Jordan who has several
> maps. Some have U.T.M. grid ticks along with the Palestine Belt grid ticks,
> other maps have only the Palestine Belt Grid ticks, and he'd like to be
> able to integrate his data and convert it to U.T.M. As I said, I have no
> problem finding the Palestine 1928 datum, and as none of his maps mention
> any other datum, I suspect that no datum transforms will be required. This
> is also suggested by the fact that the most recent maps indicate that they
> were made in 1978, which predates GRS80 and WGS84.
> 
>
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Re: MI Lambert Salvador

[Cliff Mugnier - University of New Orleans]

Damien,

Presumably the math model in MapInfo is a "Kosher" Lambert Conformal Conic and
is fully conformal.  Therefore, it is acceptable for use in El Salvador.  Note,
however, it is NOT suitable for use in France for coordinates determined prior
to 1948.  That is the year the country of France changed from the old French
Army Truncated Cubic math model to the fully conformal math model which is
probably in MapInfo.  

Beware of working in areas and countries that used to be French Colonies.  With
the exception of "new" stuff in Algeria (they changed the math model in the 70's
or 80's I think), ALL other foreign French Stuff is the old Truncated Cubic if
it is on the Lambert.  (Of course, many other projections have been used also by
the French for large-scale topo and hydro work.)

Don't forget that El Salvador uses one zone but it has two Datums.  (Ocotepecque
Datum of 1935 and NAD 1927.)  See my column from July 1999 in "Photogrammetric
Engineering and Remote Sensing, or you can download the paper (about neighboring
Honduras), under Grids and Datums stuff from:

http://www.asprs.org/resources.html

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

Voice: (504) 280-7095
Facsimile: (504) 286-1200
---
Damien CHAMINADE wrote:
> 
> I work with data from Salvador. The used projection is Lambert.
> 
> I have modified the file MapInfow.prj accorded to the parmeters got in the
> National Institute delaing with geographical data. There are correct.
> 
> 1) I would like to know wether the Lambert defined in MapInfo is only
> correct for France, or it may be used for any country.
> 
> 2) Is there anybody who has already worked with data from Salvador?
> 
> Thanks,
> 
> D. Chaminade
> 
> --
>
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MI Re: polyhedric projection

[Cliff Mugnier - University of New Orleans]

Terry,

The Polyhedric is a very old projection used mainly in the 19th Century.  It is
a sheet-by-sheet sort of thing, where adjoining sheets are individual and
separate projections.  The graticule fits together more or less when you attempt
to paste two or more sheets together, but trying many sheets will result in
physical holidays.  It is similar to the screwy way the old American Polyconic
works, but it is a different projection.  It was invented for mapping by
planetable and alidade.  It was extensively used by the Austro-Hungarian Empire.

I don't think John P. Snyder did much with it because the USGS did not use it.

This is still used by the Germans for their small scale topographic maps
intended for sale to tourists for hiking.  It's still found in (formerly Dutch)
Indonesia, Tampico, and was probably used a LONG time ago in Aruba, Curacao, and
Sint Maartin.  Argentina used to use it, and Uruguay still (I think) uses it for
their 1:200,000 military topo series.

Mathematically, the closest thing current canned software packages might come is
the Local Space Rectangular (LSR) where the geocentric coordinates of an origin
point (center of the sheet) is used as a point of tangency to the ellipsoid.  A
three-dimensional orthogonal rotation matrix is computed to "pop" all geocentric
coordinates into a tangent plane (or secant plane if you want to diddle with a
scale factor).  Just constrain all of your transformed plane coordinates to
local Z=0 meters.  The inverse is just as easy since the inverse of a direction
cosine matrix (orthogonal coordinate system) is equal to its transpose.

In this implementation, the LSR is the same as a Polyhedric ("Polyeder" in
Dutch), and is an ellipsoidal gnomonic.  I have discussed this in a couple of my
past columns in "Photogrammetric Engineering and Remote Sensing."

The equations are in the third and fourth editions of the Manual of
Photogrammetry.

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

Voice and Facsimile: (504) 280-7095
-
Terry D. Peterson wrote:
> 
> Dr. Mugnier,
> 
>   Just a quick question.  According to a client who is using our
> software old Japanese geologic maps are drawn in the polyhedric
> projection which I had never even heard of before his email.  In doing a
> search on the net, I did find some information but no equations, etc.
> Unfortunately, I am unable to locate our copy of the latest Synder
> book.  Do you happen to know anything about this projection?
> 
>   Thank you in advance for any help that you can provide.
> 
> ==
> Terry D. PETERSON
> MicroImages Technical Sales Engineer
> MicroImages, Inc.
> 11th Floor - Sharp Tower
> 206 South 13th Street
> Lincoln, NE 68508-2010
> voice: 402.477.9554
> fax: 402.477.9559
> email: [EMAIL PROTECTED]
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Re: MI Importing Autocad .dwg file to BNG

[Cliff Mugnier - University of New Orleans]

Andrew,

My guess is that you may have mixed up the order of the components of your
coordinates in some way.  For example,

Your BNG example for

X = 429362.55
Y = 414762.18

correctly corresponds to 

Lat = 53* 37' 41.9919" N
Lon = -1* 33' 21.4452" W.

If we swap Lat and Long components and compute an inverse we get:

X = 7889856.582 (not even close to your problem), and

Y = -5,833,524.920 which is suspiciously close to your problem.

The reason I point this out is that some software likes cartesian coordinates to
be entered Easting, Northing, some requires Northing, Easting.

Just a thought.

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

Voice and Facsimile: (504) 280-7095

Hayes, Andrew wrote:
> 
> Hi all,
> 
> I am pretty naive when it comes to projections etc.
> 
> I have received an Autocad .dwg file and it is requested that I import this
> into MapInfo in British National Grid.
> 
> MapInfo only seems to allow the importing of autocad.dxf files, so I
> converted the file to MI.tab file using Geographic Explorer Quick
> Translator.  The resulting file comes in with Non-Earth Meters projection.
> Upon converting it to BNG projection when saving a new copy, the copy still
> loads in the same place (miles away from where I want it) with an example
> being x=1051925.36 y=-5112608.9 as compared to x=429362.55 and y=414762.18,
> as required.
> 
> I have tried to update the x & y centroids without success.
> 
> Does anyone have any suggestions??
> 
> Thanks in advance,
> 
> Andrew Hayes
> GIS Analyst/Programmer
> Wakefield MDC
> > Web:   http://www.wakefield.gov.uk/
> E-mail: [EMAIL PROTECTED]
> Tel: 01924-(30)5440
> Fax: 01924-(30)5424
>
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MI Re: Namibia projection info

[Cliff Mugnier - University of New Orleans]

Iain,

The Namibian Datum is based on the origin point, "Schwarzek"  near Gobabis
where:

Lat = -22* 45' 35.820" South,
Lon = +18* 40' 34.549" East of Greenwich.

The ellipsoid of reference is the Bessel 1841, but it was implemented with the
"Legal Metre."  When expressed in International meters (S.I.),
a = 6,377,483.865 meters
b = 6,356,165.383 meters.

The transformation from the Nabibian Datum to WGS84 is:

dX = +616.6 meters, +/- 1.3 m.,
dY = +103.0 meters, +/- 1.3 m.,
dZ = -256.6 meters, +/- 1.3 m.

(Higher order transformations exist in the literature, but are not recommended
for practical use in Namibia).

The Grid System used is the "Southwest Africa Belts."

Math model used is the Gauss-Kruger Transverse Mercator.

Central Meridians: 13*E, 15*E, 17*E, 19*E, 21*E, 23*E, and 25*E,
Scale Factor @ Origin is Unity,
False Northing Latitude @ Origin is -22* 00'00" South,
False Easting and False Northing are zero.

If you contact them at:

Surveyor General,
Directorate of Surveys
Private Bag 13182
9000 Windhoek
Republic of Namibia,

>>>-> Don't forget to write in German!!! <-<<<

For other countries, I publish monthly in "Photogrammetrc Engineering and Remote
Sensing."  My column is called Grids and Datums, and a number of past issues are
available from the society's web site at:

http://www.asprs.org/resources.html

I did nearby Mozambique (Portuguese stuff) in September 1999, and Madagascar
(French stuff) is available for free downloads from this month's issue (Feb
2000).  Consider joining the society; it's the best journal in English that
covers the entire field of GIS.  Plus, it's the only one that features me! :-)

Viel Gluck!

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])   Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering LaboratorySurveying, Geodesy & Photogrammetry
Department of Civil Engineering   Department of Civil Engineering
UNIVERSITY OF NEW ORLEANS LOUISIANA STATE UNIVERSITY
New Orleans, Louisiana  70148 Baton Rouge, Louisiana 70803

Voice (504) 280-7095  Voice (225) 388-8536




Iain Allen wrote:
> 
> Hi Dr. Mugnier,
> 
> I am looking for projection information for Namibia and I was told you would be a 
>good person to
> ask.
> 
> I have projected data for Namibia, but I have no projection information. Do you have 
>any idea what
> projection(s) may be commonly used for Namibia.
> 
> Thanks,
> 
> Iain Allen
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Re: MI Mysterious coordinate system

[Cliff Mugnier - University of New Orleans]

Alex Eshed wrote:
> 
> Season's Greetings, List.
> 
> Here in Israel the use of WGS 84, Zone 36 Northern Hemisphere,
> is pretty common. Digitized maps (from paper maps) show a high
> level of accuracy compared to ground surveying data in this
> projection. However, GPS (differential) readings are off by a few
> dozen meters.
> 
> But... when using a projection called UTM ED 50 the GPS readings
> are far more accurate.
> 
> Can anyone explain to me what's happening? And what is UTM ED
> 50 anyway?
> 
> TIA to all responders.
> 
> Best regards,
> Alex Eshed
> Digi-Tek Ltd.
> 12, Homa St., Rishon LeZion, 75655, Israel
> Tel: +972-3-961-5840
> Fax: +972-3-961-5877
> mailto:[EMAIL PROTECTED]
> http://www.dgtek.com
>

Alex,

Here's the explanation for your question in as short a treatise as I can make
it:

A "Datum" is a system of Latitude and Longitude that is traditionally
established by individual countries. In Israel, the traditional system is the
Palestine Datum of 1928.

After WWII, the U.S. Army Map Service (AMS) decided that it was going to "unify"
all of the individual Datums that had connections with each other from classical
surveying observations.  That new "Datum" was going to be started in 1950 in
Europe. In particular, France was the first country to be "converted" to the
European Datum 1950 (EU50).  Each country in Western Europe was connected to
EU50 through their connections to France, then Scandanavia was connected in the
Northern European Block, and Institue Geographique National (IGN) in France was
contracted to do the connection computations in Northwest Africa (through AMS
computations in Spain and Portugal).  After the Danube region of Europe was
adjusted and connected with Western Europe, the chains of triangulation into
Greece and Turkey were computed on EU50, and then the Palestine Datum was
recomputed onto EU50 in the process of bringing EU50 to Egypt and connection
with EU50 in Algeria as computed by the French IGN.

These computations were done with the use of the Universal Transverse Mercator
(UTM) Grid which is composed of 60 zones, each 6 degrees wide in longitude.  UTM
is a Grid, and is independant of ellipsoids and Datums.  UTM is based on the
Transverse Mercator projection, and the mathematical formulae are specifically
called the Gauss-Kruger model.

For further information on this stuff, I publish a monthly column on the topic
of "Grids and Datums" (each month is the history of all systems, new and old,
existing in a particular country).  I publish in "Photogrammetric Engineering
and Remote Sensing," the official journal of the American Society for
Photogrammetry and Remote Sensing.

You can download some of my past "Grids and Datums" columns from:

http://www.asprs.org/resources.html

The files are in Adobe Acrobat PDF format, and there is a link at that page
where you can download a free copy of Acrobat to read and print each copyrighted
article.

There's ten different countries on the list at the moment, two discuss some of
the history I just alluded to above.  See specifically my column from June, 1998
on the Kingdom of Morrocco, and my column from October, 1998 on the Kingdom of
Belgium.  (There's lots of other places, but that's what's available on EU50
stuff.  I did one a few months ago on the Kingdom of Norway, but the Society
does not have that one available as a "freebie."

It ain't a mystery; it's just remarkably obscure stuff.

One of the world's foremost authorities on Map Projections is Prof. Ron K. Adler
who teaches at several campuses (campii?), including in Tel Aviv.

Happy Holidays to you too!

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

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MI Old Hawaiian Datum

[Cliff Mugnier - University of New Orleans]

Will,

Old Hawaiian Datum origin is at Oahu West Base where:
Latitude = 21* 18' 13.89" North,
Longitude = 157* 50' 55.79" West of Greenwich
The reference azimuth to Oahu East Base is
291* 29' 36.0 (from South) and the ellipsoid of
reference is the Clarke 1866.

The Old Hawaiian Datum is based on an adjusted Latitude
derived from a number of Astronomic Latitudes observed in
various parts of the islands, hence the term "mean."  It is
also based on an adjusted Longitude derived from a number of 
Astronomic observations in various parts of the islands that 
included lunar culminations, stellar occultations, etc., 
hence the term "mean" also. 

For a detailed description of the origin, see U.S. Coast & 
Geodetic Survey Special Publication No. 156, "Triangulation
in Hawaii."

I do not have any information regarding the geometric relation
between the Old Hawaiian Datum and NAD1927, but I would guess
that the differences are probably minimal, mostly in Longitude, 
if any.  (S.P. 156 would have the definitive answer, I do not 
have a copy.)  On the other hand, the difference to NAD83 should 
be a whopper!

Let me know if you need further help.

Cliff

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

Voice and Facsimile: (504) 280-7095

Mitchell, Will wrote:
> 
> Hello Cliff,
> 
> Pardon me if this is an obvious or unwelcome question, but - can you tell me
> anything about the Old Hawaian Mean datum, or refer me to good reference
> material on it?
> 
> I must admit I get quite mixed up in this arena (datums and projections).
> I'm simply trying to use data in MapInfo that I believe to be State Plane
> NAD27 HI Zone 3, and I don't know how NAD27 equates to Old Hawaian Mean
> (this was referred to in a different data source).
> 
> Thanks.
> 
> Will Mitchell
> GIS Manager
> The Environmental Company, Inc.
> Charlottesville, Virginia
> 804-295-4446
> [EMAIL PROTECTED]
>
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MI Sri Lanka National Grid System

[Cliff Mugnier - University of New Orleans]

John,

The Kandawala Datum of 1929 origin is at Latitude = 7* 14' 06.838" North,
Longitude = 79* 52' 36.670" East of Greenwich.  The reference azimuth to station
Halgastota = 176* 41' 33.18", and the ellipsoid of reference is the Everest 1830
where a = 6,377,276.345 meters and first eccentricity squared is
0.00663784663020.   The scale of the triangulation of the island is dependant on
two bases, each about 5 1/2 miles long, situated at Negombo on the West Coast
(Latitude 7* 10'), and at Batticaloa on the East Coast (Latitude 7* 40')  These
bases were originally measured in 1857 and 1859 respectively, remeasured in
1930.  The bases agree to 1 in 115,000.

The National Grid System is the Ceylon (Sir Lanka) Transverse Mercator Belt
which is based on the abbreviated Gauss-Kruger (truncated at the fifth
derivative term). The Central Meridian is 80* 46' 18.16" East,  The False
Northing Latitude of Origin is 7* 00' 01.7290" North, the Scale Factor at Origin
is unity, and both the false northings and false eastings are 176,000 Indian
Yards where one meter is equal to 1.093619000 Indian Yards.

The International Boundary between Sri Lanka is much simpler than that of
Norway.  Your country uses the Principle of Straight Baselines, but the Sri
Lankans use "Great Circle Arcs" (ellipsoidal geodesics) to define their limits
with coordinate points that are expressed in Latitude and Longitude.

Check out the website for the American Society for Photogrammetry and Remote
Sensing at 

http://www.asprs.org/resources.html

Under the heading of "Grids and Datums" are a number of my past columns on
various countries, Norway will be the featured country next month (October,
1999).  

Cliff Mugnier

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

Voice and Facsimile: (504) 280-7095
-
Dehls John wrote:
> 
> Does anyone know the details of the Sri Lankan national grid system? ie
> projection type and parameters?
> 
> John
> 
> Dr. John F. Dehls
> 
> Geological Survey of Norway
> N-7491 Trondheim
> Norway
> +47 73 90 44 54 - office
> +47 73 92 16 20 - fax
> 
> **
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Re: MI Argentina

[Cliff Mugnier - University of New Orleans]

Try

http://www.igm.gov.ar/

Stuff is not free.

De nada.

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

Voice and Facsimile: (504) 280-7095
--
Jon Spinney wrote:
> 
> Hello list,
> 
> Does anybody know where I can get Argentina data sets? I need to match these
> records to a Provinces data set- polygons.
> 
> Flores, Caballito, Parque Centenario, Recoleta, Retiro, Congreso, Palermo,
> Saavedra, Nuñez, Belgrano, Vicente Lopez, Olivos, La Lucila, Martinez, San
> Isidro, Beccar, La Horqueta and San Fernando.
> 
> Muchos Gracias,
> 
> Jon Spinney
> [EMAIL PROTECTED] 
> 
> --
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MI Re: Chamberlin Trimetric Projection

[Cliff Mugnier - University of New Orleans]

Denise,

The Chamberlin Trimetric Projection is an old thematic type of projection cooked
up by the Chief Cartographer of the National Geographic Society back in the late
19th century.  It looks really nice, but is a contrivance that attempts to
display a map with features that are equally distanced from three separate
points.  Such a contrivance is impossible, but Chamberlin's attempt is a pretty
good compromise.  The Society still uses it, and it still looks really nice. 
That is a characteristic of most National Geographic Society Maps; not only are
they accurate and useful, but they are actually framed and put up for display in
people's homes - not just in offices.

One problematic feature of this projection is that after it is drafted,
color-separated and printed, the copyrighted map that is not supposed to be
copied or put into digital form of any kind is downright difficult to digitize. 
That is, it's easy to digitize in terms of digitizer (x,y) coordinates, but the
inverse computation to Latitude and Longitude is a "zinger."  

In the late John P. Snyder's work, "Map Projections - A Working Manual," U.S.
Geological Survey Bulletin 1395, he lists it in two places in the index.  The
first time he covers it is in the section on pseudo conics, and specifically the
ellipsoidal Bonne, the second time he mentions it in another context of
contrived projections that give a hint.  The old AT&T projection is, according
to Mr. Snyder, an ellipsoidal projection that is roughly equivalent to the
Chamberlin Trimetric.  Although obscure, the math for that can be scrounged from
old Bell Labs reports occasionally found in various libraries.  

The old cartographic trick of "paneling" for changing projections with a razor
blade and paste could be used with a rubber-sheet transformation, but that is
using brute force rather than mathematical elegance.

Another thing you could do is go to the horse's mouth.  Ask the National
Geographic Society and see what they have to say.  I imagine they are going to
ask you why you want to know the mathematical details of one of THEIR
projections ...

Specifically with respect to MapInfo, I have no idea how to help you.  My claim
to fame is definitely NOT specific software commands or procedures.

Good luck,

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

Voice and Facsimile: (504) 280-7095
--
Denise wrote:
> 
> Hi
> 
> I have seem numerous posts of yours on Mapinfo-L and
> am hoping you can help me with information on this
> projection. I have MapInfo, but it does not seem to
> support this projection.  Do you know how I would
> go about finding more information on this projection
> and then how I would use such info in MapInfo?
> 
> Denise
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MI Flavors of Transverse Mercator

[Cliff Mugnier - University of New Orleans]

Fernando,

The GCTP.FOR is a Fortran77 source file (free from the "USGS.gov" websites) for
all of the map projections used by the U.S. Geological Survey.  There are two
data files associated with the source code that are included also.  The math was
documented by John P. Snyder (now deceased) in "Map Projections Used by the U.S.
Geological Survey" Bulletin 1532, and later revised as "Map Projections - A
Working Manual" Bulletin 1535.  Bulletin 1535 is better because it has more
projections and Mr. Snyder referenced me (ha, ha)!   :-)

Anyway, Dr. Atef Elassal (now retired), then translated 1532 into Fortran for
the USGS.  That is GCTP - the General Cartographic Transformation Package which
is specifically for cartographic applications within the United States.  That's
what the data files are for.  GCTP is absolutely perfect for what it was
intended for - INSIDE THE UNITED STATES OF AMERICA ONLY ! ! ! ! ! 

Many, many commercial software packages worldwide use this as the basic
foundation for their coordinate transformation engine.  I give it away to my
students as an example of "how not to do it."  This is essentially useless for
geodetic applications outside of the United States.  It can oftentimes be used
for cartographic applications outside of the U.S. IF AND ONLY IF the
computational accuracy (and precision) is not needed for mapping at scales
larger than 1:24,000!!!

If you are going to use this for a NON-geodetic application, this will do just
fine.  If you are doing geodesy, do not touch this code!

--

The ellipsoidal case of the Transverse Mercator was cooked up by Heinrich
Lambert in the middle 1700's.  It was a mathematical curiousity that was useless
for practical applications until the City of Hannover asked Professor Carl
Freiderich Gauss to do a geodetic survey of the city in preparation for a new
set of accurate tax maps.  

There are two things you cannot avoid in life; those are death and taxes.  Most
all geodetic research has been funded (since the late 1700's) for either tax
mapping purposes or military purposes looking for better and more efficient ways
of killing people ...

Anyway, Gauss worked up an expansion of Lambert's formulae that his Ph.D.
students could follow in doing the grunt work of adjusting the Hannover
Triangulation Net on the Gauss-Conformal Transverse Mercator.  Years later, a
Prussian Artillery Office named Schreiber used a simplified form of the
Gauss-Conformal Transverse Mercator that was a specific truncation called the
Gauss-Schreiber Transverse Mercator.  Another Prussian Artillery Officer named
Krüger came up with a more elaborate expansion of the infinite series.  Yup, it
is called the Gauss-Krüger Transverse Mercator.  In the 1920's or 1930's an
Italian Professor in Italy came up with a local version for the Instituto
Geografico Militare, and his name was Boaga.  Yup, the Italians use the
Gauss-Boaga Transverse Mercator.  And so on and so forth for ALL the ellipsoidal
projections used for Grids on topographic maps.

When looking at geodetic accuracy and computational precision at the
sub-millimeter level TO THE MULTI-METER LEVEL for coordinates many degrees east
or west of the central meridian, the specific truncation of a Transverse
Mercator makes a big difference. Doing foreign work for bazillion-dollar
exploration, drilling, and production for oil wells in specific countries?  Pay
attention to your math. If you are doing UTM or DHG (Deutches Herres Gitter)
within a plus or minus 3 degree longitude distance from the Central Meridian, it
will do fine.

Diddling with some X,Y coordinates for a Ph. D. dissertation?  Unless your Major
Professor is a geodesist or mathematical cartographer, they won't even know the
difference.

Cliff

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

Voice and Facsimile: (504) 280-7095
---
Fernando wrote:
> 
> Hello Cliff
> 
> I am doctorate student that needs to program a convert from Gauss
> Krüger to lat. long and back. The ideal solution would be to get a
> Fortran code for this, but maybe that is too much luck, so I would be
> happy with any hint you can give me (if I do not have to buy any
> software or module, even better).
> 
> I have already spent a lot of time looking for it in Internet and I have
> found nothing, except your name in 'users.netonecom.net' (1998).
> 
> And I have another question that confuses me (I am a beginner on this):
> Is Gauss-Krüger the same Transverse Mercator, or there is an important
> difference?
> 
> Thanks in advance for any help,
> 
> Fernando
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Re: MI coordsys transformation

[Cliff Mugnier - University of New Orleans]

Walter and Jacques,

I disagree with the 6-parameter suggestion.  I do not believe anything more than
a 3-parameter is reasonable to transform between a local archeological "Dig"
coordinate system and a geodetic system.

When I say 3 parameters, I mean a change in X coordinates, a change in Y
coordinates and a rotation.  For that sort of operation, Walter is correct in
that such a transformation can be done with a minimum of two points.  I would
like to suggest that more points be used as a check, but a unique solution is
satisfied with 2 points.  The 6-parameter solution offers 3 additional
parameters that should not be tolerated in such a survey.  A different scale in
each coordinate axis along with a factor for a non-orthogonal axis angle is
totally out of place.

Textbook for this sort of thing?  Good Grief!

   X =   X' cosine (theta) + Y'   sine (theta) + dX'

   Y = - X'   sine (theta) + Y' cosine (theta) + dY'

Presumably, the primed components are the "Dig" coordinates.  This is not rocket
science, it is High School Analytical Geometry.

This will be adequate for a "DIg" no larger than 1,000 acres or a linear feature
less than 5 miles long.  Bigger than that, and you should be working in a truly
Geodetic coordinate system that is a conformal (orthomorphic) Grid system with
corrections for azimuth, scale factor, and correction to mean sea level. 
However, something that big is probably going to have a surveyor associated with
the project and therefore they will take care of the details.

This can be extended into a local geodetic grid in itself if the geodetic
coordinates of the origin point is known along with a true meridian reference
(azimuth from true north).  With that accomodated, then the local "Dig"
coordinate system can be either an ellipsoidal polyhedric (similar to a
gnomonic), or can be an ellipsoidal azimuthal equidistant.  Both techniques have
been effectively used for islands and small countries in the 19th and 20th
centuries.

Examples of the French used of the ellipsoidal Hatt Azimuthal Equidistant
projection for such "localized" surveys can be found in my "Grids and Datums"
column on the Republic of Gabon, published in the September, 1998 issue of
"Photogrammetric Engineering and Remote Sensing" and is downloadable from the
society's website at:

http://www.asprs.org/resources.html

Note that the file is in Adobe Acrobat ".pdf" format.

In conclusion, use a 3-parameter transformation, and only a 3-parameter.

Cliff

-- 
Clifford J. Mugnier ([EMAIL PROTECTED])
The Topographic Engineering Laboratory
Department of Civil and Environmental Engineering
UNIVERSITY OF NEW ORLEANS
New Orleans, Louisiana  70148

Voice and Facsimile: (504) 280-7095
---
Jacques Paris wrote:
> 
> Walter,
> 
> Have you considered using the AFFINE clause that could register any DXF in
> any "orthogonallly projected" or non-earth coordsys? The only delicate point
> is the calculation of the 6 parameters, difficulty residing essentially in
> the understanding of the direction of the change.
> 
> I have detailled that question in chap 8 Registering a DXF map in "My Bag
> o'Tricks". I must have some Excel spreadsheet that would help in the
> computation of those parameters; if you think it could be of help, ask and
> I'll see what I can do.
> 

> >
> > Hello mappers,
> > Are there some experts on coordsys transformations out there? In
> > the field Arheologists often work with a local coordsystem
> > (nonearth meters). During the gis analysis we want to place all
> > the information in an national non-earth(meters)coordsys.
> > Until now I used Rotator from the ftp-site. This works very
> > well, but I need to determine the angle of rotation and the
> > X, Y translation parameters. I think, it would be better to
> > digitize the excavation drawings directly in the
> > national nonearth coordsys by using control points from which
> > the national coordsys coordinates are used
> > (there are always points in the field from which both coordsys
> > coordinates are known).
> >
> > I would like to build a program (mbx) that asks the user- from
> > two points(is this enough?), both local and
> > national coordinates. The program then calculates the rotation
> > angle and the translation parameters. Then the user can give
> > a number of local coordinates and the program can calculate from
> > every local coordinates the national coordinates.
> > Is this possible with some simple goniometry and pythagoras?
> > Is there some information on this subject (books, internet)?
> >
> > Walter
> >
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