problem with a custom projection (Balkans 7)

[Caroline Hilton]

Hi all. I wonder if someone can help me here?

I have to create a custom coordinate system in MapInfo for MGI/Balkans
zone 7.
This is the parameters that I used in the MapInfo projection file.
"MGI / Balkans zone 7", 8, 9999, 10, 574.027,
170.175,401.545,-0.000023697, 0.0000032252, 0.000064222, 0.0000068893,
0, 7, 21,0, 0.9999, 7500000, 0

The coordinate system does exist in ArcGIS. I open the file I have in
ArcGIS using the MGI/Balkans Zone 7 coordinate system and then convert
it to Lat/Long WGS84. I do the same with the file in MapInfo, using my
custom coordinate system and them Lat/Long WGS84. When I open the lat/
long .shp file in MapInfo, it plots about 57m NE of where the MapInfo
file plots.

Did I do something wrong when creating my custom projection?

More information on parameters used below.

The projection parameters are the following:

PROJCS["MGI / Balkans zone 7",
GEOGCS["MGI",
DATUM["D_MGI",
SPHEROID["Bessel_1841",6377397.155,299.1528128]],
PRIMEM["Greenwich",0],
UNIT["Degree",0.017453292519943295]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",21], Origin’s longitude
PARAMETER["scale_factor",0.9999],
PARAMETER["false_easting",7500000],
PARAMETER["false_northing",0],
UNIT["Meter",1]]

The datum parameters are as follows;

[Datum]
dx=574.027000
dy=170.175000
dz=401.545000
Type=User Defined BursaWolf
rotX=-0.0000236970
rotY=0.0000032252
rotZ=0.0000642220
dS=0.0000068893

The parameters used in ArcGIS is as follows;

False_Easting 7500000.000000000000000000
False_Northing 0.000000000000000000
Central_Meridian 21.000000000000000000
Scale_Factor 0.999900000000000010
Latitude_Of_Origin 0.000000000000000000
Name: GCS_MGI
Angular Unit: Degree (0.017453292519943299)
Prime Meridian: Greenwich (0.000000000000000000)
Datum: D_MGI
Spheroid: Bessel_1841
Semimajor Axis: 6377397.155000000300000000
Semiminor Axis: 6356078.962818188600000000
Inverse Flattening: 299.152812799999990000

Thanks in advance if anyone can help!

regards
Caroline

[David R Sherrod]

Caroline, it must sting to get within 57 m after all the work of manipulating the custom datum conversion.

My only suggestion is with the scale factor for the conversion, an element typically defined by variable m or k but in your case apparently by dS.
I think it is reported as parts per million for purpose of the mapinfo coding.  So your "dS=0.0000068893" would be entered as 6.8893.  (It's 6.8893 x 10e6, but you needn't bother with the exponential part of the value.)

That's my guess.  Probably like you, I muck with this stuff by trial and error.  You might try my suggestion and see if it removes the 57 m shift.  If so, you owe me a six-pack of favorite beverage; if not, then I'll buy.
--------------------------------------------
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:	Caroline Hilton <pelican.g...@gmail.com>
To:	MapInfo-L <mapi...@googlegroups.com>
Date:	12/03/2010 01:21 AM
Subject:	[MI-L] problem with a custom projection (Balkans 7)
Sent by:	mapi...@googlegroups.com

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[Caroline Hilton]

Thanks David. I'll give it a go. Very much hoping I owe you a 6-pack!

Caroline

On Dec 3, 3:52 pm, David R Sherrod <dsher...@usgs.gov> wrote:
> Caroline, it must sting to get within 57 m after all the work of
> manipulating the custom datum conversion.
>
> My only suggestion is with the scale factor for the conversion, an element
> typically defined by variable m or k but in your case apparently by dS.
> I think it is reported as parts per million for purpose of the mapinfo
> coding.  So your "dS=0.0000068893" would be entered as 6.8893.  (It's
> 6.8893 x 10e6, but you needn't bother with the exponential part of the
> value.)
>
> That's my guess.  Probably like you, I muck with this stuff by trial and
> error.  You might try my suggestion and see if it removes the 57 m shift.
> If so, you owe me a six-pack of favorite beverage; if not, then I'll buy.
> --------------------------------------------
> 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

> dsher...@usgs.gov
> -----------------------------------------

>
> From:
> Caroline Hilton <pelican.geograph...@gmail.com>
> To:
> MapInfo-L <mapi...@googlegroups.com>
> Date:
> 12/03/2010 01:21 AM
> Subject:
> [MI-L] problem with a custom projection (Balkans 7)
> Sent by:
> mapi...@googlegroups.com
>

> Hi all. I wonder if someone can help me here?
>
> I have to create a custom coordinate system in MapInfo for MGI/Balkans
> zone 7.
> This is the parameters that I used in the MapInfo projection file.
> "MGI / Balkans zone 7", 8, 9999, 10, 574.027,
> 170.175,401.545,-0.000023697, 0.0000032252, 0.000064222, 0.0000068893,
> 0, 7, 21,0, 0.9999, 7500000, 0
>
> The coordinate system does exist in ArcGIS. I open the file I have in
> ArcGIS using the MGI/Balkans Zone 7 coordinate system and then convert
> it to Lat/Long WGS84. I do the same with the file in MapInfo, using my
> custom coordinate system and them Lat/Long WGS84. When I open the lat/
> long .shp file in MapInfo, it plots about 57m NE of where the MapInfo
> file plots.
>
> Did I do something wrong when creating my custom projection?
>
> More information on parameters used below.
>
> The projection parameters are the following:
>
> PROJCS["MGI / Balkans zone 7",
> GEOGCS["MGI",
> DATUM["D_MGI",
> SPHEROID["Bessel_1841",6377397.155,299.1528128]],
> PRIMEM["Greenwich",0],
> UNIT["Degree",0.017453292519943295]],
> PROJECTION["Transverse_Mercator"],
> PARAMETER["latitude_of_origin",0],

> PARAMETER["central_meridian",21], Origin?s longitude

[Caroline Hilton]

Hi David

Sadly, this didn't make any difference. Neither, oddly, did playing
around with
the positive and negative signs, so I'm none the wiser about this
errant 57m...

Still, worth a try, thanks.

Cheers

Caroline

On Dec 3, 3:52 pm, David R Sherrod <dsher...@usgs.gov> wrote:

> Caroline, it must sting to get within 57 m after all the work of
> manipulating the custom datum conversion.
>
> My only suggestion is with the scale factor for the conversion, an element
> typically defined by variable m or k but in your case apparently by dS.
> I think it is reported as parts per million for purpose of the mapinfo
> coding.  So your "dS=0.0000068893" would be entered as 6.8893.  (It's
> 6.8893 x 10e6, but you needn't bother with the exponential part of the
> value.)
>
> That's my guess.  Probably like you, I muck with this stuff by trial and
> error.  You might try my suggestion and see if it removes the 57 m shift.
> If so, you owe me a six-pack of favorite beverage; if not, then I'll buy.
> --------------------------------------------
> 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

> dsher...@usgs.gov
> -----------------------------------------
>
> From:
> Caroline Hilton <pelican.geograph...@gmail.com>

> To:
> MapInfo-L <mapi...@googlegroups.com>
> Date:
> 12/03/2010 01:21 AM
> Subject:
> [MI-L] problem with a custom projection (Balkans 7)
> Sent by:
> mapi...@googlegroups.com
>

> Hi all. I wonder if someone can help me here?
>
> I have to create a custom coordinate system in MapInfo for MGI/Balkans
> zone 7.
> This is the parameters that I used in the MapInfo projection file.
> "MGI / Balkans zone 7", 8, 9999, 10, 574.027,
> 170.175,401.545,-0.000023697, 0.0000032252, 0.000064222, 0.0000068893,
> 0, 7, 21,0, 0.9999, 7500000, 0
>
> The coordinate system does exist in ArcGIS. I open the file I have in
> ArcGIS using the MGI/Balkans Zone 7 coordinate system and then convert
> it to Lat/Long WGS84. I do the same with the file in MapInfo, using my
> custom coordinate system and them Lat/Long WGS84. When I open the lat/
> long .shp file in MapInfo, it plots about 57m NE of where the MapInfo
> file plots.
>
> Did I do something wrong when creating my custom projection?
>
> More information on parameters used below.
>
> The projection parameters are the following:
>
> PROJCS["MGI / Balkans zone 7",
> GEOGCS["MGI",
> DATUM["D_MGI",
> SPHEROID["Bessel_1841",6377397.155,299.1528128]],
> PRIMEM["Greenwich",0],
> UNIT["Degree",0.017453292519943295]],
> PROJECTION["Transverse_Mercator"],
> PARAMETER["latitude_of_origin",0],

> PARAMETER["central_meridian",21], Origin?s longitude

[Richard Greenwood]

Caroline,

I'm a little confused by the original post. If I understand correctly,
the MapInfo and ESRI conversions differ by ~50 meters, but do you know
that the ESRI conversion is "correct"? Do you have a third conversion
tool that you are comparing against? Is there an EPSG code for the
system (3908 maybe?) or some other authoritative source?

Can you provide a single example point in the projected coordinate
system and what you believe to be the correct WGS84 lat/long for the
same point?

Regards,
Rich

--
Richard Greenwood
richard....@gmail.com
www.greenwoodmap.com

[Caroline Hilton]

Hi Richard

Thanks for this insight - you were right, the ESRI one didn't appear
to be quite right either, so we created another one in Arc based on
the new parameters, and it now seems to make sense compared to a 3rd
set of data. So... I *think* we might be there!

Thanks again,

regards
Caroline

On Dec 5, 1:00 am, Richard Greenwood <richard.greenw...@gmail.com>
wrote:

> Caroline,
>
> I'm a little confused by the original post. If I understand correctly,
> the MapInfo and ESRI conversions differ by ~50 meters, but do you know
> that the ESRI conversion is "correct"? Do you have a third conversion
> tool that you are comparing against? Is there an EPSG code for the
> system (3908 maybe?) or some other authoritative source?
>
> Can you provide a single example point in the projected coordinate
> system and what you believe to be the correct WGS84 lat/long for the
> same point?
>
> Regards,
> Rich
>
> On Sat, Dec 4, 2010 at 10:47 AM, Caroline Hilton
>

> --
> Richard Greenwood
> richard.greenw...@gmail.comwww.greenwoodmap.com

[Richard Greenwood]

You know what they say - "the man with two watches never knows what
time it is"...