Arc 1950 Zimbabwe Projection - have a problem

[Vagrant]

Good day, need help. My problem is:
They use in Zimbabwe projection Arc1950, based on Clarke ellipsoid.
Mapinfo have not metric Arc1950, just a Long-Lat Arc1950, but I need
metric.
In manual I found :

A custom datum can be defined in any coordinate system definition.
The Appendix describes how to define a coordinate system.
To define a custom datum in a coordinate system, use datum number 9999
followed by the datum parameters, in this order:

9999, EllipsoidNumber, dX, dY, dZ, EX, EY, EZ, m, PrimeMeridian

Then I found a features of Arc 1950:

Number Ellipsoid a 1/f
15 Clarke 1880 (modified for Arc 1950) 6378249.145326
293.4663076

and parameters
(http://surveying.wb.psu.edu/sur351/DatumTrans/
datum_transformations.htm)


Geodetic Datum Transformation Parameters (Local to WGS-84)
d = delta in meters; e = error estimate in meters; #S = number of
satellite measurement stations
Datum Ellipsoid dX dY dZ Region of
use eX
eY eZ #S
Arc 1950 Clarke 1880 -143 -90 -294 MEAN FOR
Botswana; Lesotho; Malawi; Swaziland; Zaire; Zambia; Zimbabwe 20
33 20 41

After that I made a cistom projection (35 South, prm.meridian 27):

"ZimArc1959 35S", 9999, 15, -143, -90, -294, 20, 33, 20, 293.4663076,
27

Second run:
"Arc_1950_UTM_Zone_35S, Southern Hemisphere (Clarke_1880_Arc)", 28,
9999, 15, 8, -142, -96, -293, 5, 8, 11, 293.466307656, 27.0

But every time have just error message. What is wrong in my strings?

[David R Sherrod]

I think your mistake is that you are trying to create a custom projection.  All you really need to do is define a standard projection line that is based on transverse Mercator projection.

For Transverse Mercator projections:
Projection                8 (transverse Mercator)
Datum                        5 (Arc 1950)
Unit                        7 (meters)
Origin Longitude        27 (I’m judging from your notes)
Origin Latitude        0 (I’m guessing at this, on basis of my experience in Tanzania)
Scale factor        0.9996
False easting        50000 (I’m guessing here, too)
False northing        10000000 (ten million; I’m guessing here)

The corresponding line that you would add to your MAPINO.PRJ file (open it in a text editor--looks like you have done that correctly).

"--- Universal Transverse Mercator (ARC 1950) ---"
"UTM Zone 35, Southern Hemisphere (Nigeria)", 8, 5, 7, 27, 0, 0.9996, 500000, 10000000


If it were me, I'd tuck it away far down in the MAPINFO.PRJ file, where you'll find many headers with the them Universal Transverse Mercator.  If you added the two lines that I'd suggest, you'll have a place to add additional lines for other zones in the Arc 1950 scheme.

PROBLEMS?  I guessed at some of your parameters.  When I find more time I'll check the scale factor, origin longitude, and false eastings and northings.  But you might run the experiment with the information I provided, perhaps thereby saving me some time.

AND FOR COMPLETENESS, I'm pasting in next the lines from my file, which I use for sections 36 and 37 (south of equator), Arc 1960, in nearby Tanzania.  You may find them helpful for comparative purposes.  These are well tested.  Arc 1950 uses 5 for the datum; Arc 1960 uses 6.
"--- Universal Transverse Mercator (ARC 1960) ---"
"UTM Zone 36, Southern Hemisphere (Tanzania)", 8, 6, 7, 33, 0, 0.9996, 500000, 10000000
"UTM Zone 37, Southern Hemisphere (Tanzania)", 8, 6, 7, 39, 0, 0.9996, 500000, 10000000


--------------------------------------------
David R. Sherrod, Cascades Volcano Observatory
U.S. Geological Survey,
1300 SE Cardinal Court, Bldg. 10
Vancouver, WA  98683
voice 360-993-8915
fax     360-993-8980
dshe...@usgs.gov
-----------------------------------------

From:	Vagrant <atel...@gmail.com>
To:	MapInfo-L <mapi...@googlegroups.com>
Date:	01/23/2012 11:32 AM
Subject:	[MI-L] Arc 1950 Zimbabwe Projection - have a problem
Sent by:	mapi...@googlegroups.com

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[David R Sherrod]

Verification for the projection data already provided.  Origin longitude 27, origin lat 0.
False easting is 500,000.  It was entered correctly in my suggested paste-in lines for MAPINFO.PRJ, but I mistyped it in my listing of the logic sequence.

Sorry to double up on the replies.


-----------------------------------------

[vagrantius]

Ok, I tried to use last variant and make a few runs more.

"--- Zimbabwe Universal Transverse Mercator (Clarke 19880 - ARC 1950) 35S, 36S ---" 

"UTM Zone 35, Southern Hemisphere (Zimbabwe)", 8, 5, 7, 27, 0, 0.9996, 500000, 10000000

"UTM Zone 35, South Clarke1950 AT (Zimbabwe)", 1008, 15, 7, -143, -90, -294, 20, 33, 20, 0.9996, 27

"UTM Zone 35, South Clarke1950 AT1 (Zimbabwe)", 1008, 15, 7, 27, 0, 0.9996, 500000, 10000000, 7, -143, -90, -294, 20, 33, 20

results:

1 string determined as Gauss-Kruger LO 27 (LO 29) Arc1950 

2  string - error - " invalide distance units: 20"

3  points on he same place as was in v.1 , image distorted (used Discover image reprojection)

String 3 was created after was found in MI User Guide (Elements of a Coordinats System):

"Assume you want to work with a simple system based on the Transverse Mercator projection and

using the NAD 1983 datum. You might have a line such as the following in your MAPINFOW.PRJ

file:

"UTM Zone 1 (NAD 83)", 8, 74, 7, -177, 0, 0.9996, 500000, 0

Now let’s say that you want a system based on this, but with an affine transformation specified by

the following parameters (see Affine Transformations in the Help System: Units=meters; A=0.5; B=-

0.866; C=0; D=0.866; E=0.5; and F=0. The required line in the MAPINFOW.PRJ file is:

"UTM Zone 1 (NAD 83) - rotated 60 degrees", 1008, 74, 7, -177, 0, 0.9996, 500000, 0, 7, 0.5, -

0.866, 0, 0.866, 0.5, 0"

But problem still exist, I can find right solution. 

Still need help.

[David R Sherrod]

If you need to do something sophisticated with affine transformations, then perhaps someone else on the list will chime in.  But it's still unclear to me just what it is you're trying to do.

Your comment  "1 string determined as Gauss-Kruger LO 27 (LO 29) Arc1950" sounds correct to me.  It suggests that you're working in a newer version of Mapinfo than I, and that they added the UTM projection scheme you wanted.  ARC 1950 transverse mercator zone 27 south is the same as Gauss Kruger LO 27 Arc1950, I think.  It was added as a Zambian projection in MI 10.5, but that seems about right for neighboring Zimbabwe.

You might state anew what the datasets are (and their datums), what you're trying to do, and what problems are they presenting.
For example
(1) Suppose you have data points that you gathered with handheld GPS receiver, and you recorded the data as ARC 1950, UTM (eastings and northings).  Your data comes with a zone number, 35.  To project that data (from a text file or excel spreadsheet), you would choose the first of your projection lines.  (8, 5, 7, 27, 0, 0.9996, 500000, 10000000)

(2) You have a topographic quadrangle map (digital raster graph), you want to project it, and you know that it was prepared as transverse Mercator, ARC 1950, zone 35S.  To project it, you would pick points during the raster georegistration step that correspond to grid crossing poins of known coordinates (eastings and northings) and then be sure to choose the first of your projection lines so that it appears correctly.

(3)  You have data points that are reported as WGS84 UTM.  You wish to project them onto other data that are already set in the ARC 1950 projection scheme, such as items 1 or 2 above.  You would register your points as WGS84 UTM, zone 35S, because that's how they were reported.  MapInfo will place them correctly onto your existing data (onscreen) because it is happy reprojecting on the fly.  You don't need to convert data just to get it positioned correctly.


-----------------------------------------

From:	vagrantius <vagra...@gmail.com>
To:	mapi...@googlegroups.com
Date:	01/24/2012 11:16 AM
Subject:	[MI-L] Re: Arc 1950 Zimbabwe Projection - have a problem
Sent by:	mapi...@googlegroups.com

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