[Proj] TM06 for Portugal

Roger Oberholtzer roger at opq.se
Tue Jun 8 23:07:25 PDT 2010


On Tue, 2010-06-08 at 09:40 +0200, Mikael Rittri wrote:
> Roger Oberholtzer wrote:
> 
> > How would you convert WGS84 lat/long into TM06 
> > northing/easting? I know that WGS84 is so close 
> > to ETR89 here that one 'could' use the WGS84 values
> > in the transform from ETRS89 to TM06. But how 
> > would I do it the 'proper' way with proj? 
> 
> For this purpose, there are seven-parameter 
> transformations that are time-dependent (since 
> the ETRS89 follows the contintental drift of 
> Eurasia, while WGS84 does not).  
> 
> The British Ordnance Survey cites the following 
> datum shift from ITRS2005 to ETRS89: 
> 
> tX =  0.056 m
> tY =  0.048 m
> tZ = -0.037 m
> rX =  0.000054 sec * deltatime
> rY =  0.000518 sec * deltatime
> rZ = -0.000781 sec * deltatime
> s  =  0 ppm
> 
> where deltatime is the difference, in years, between 
> the time when the ITRS2005 coordinates were observed,
> and the fixed epoch of ETRS89, which is 1989.0. 
> http://www.ordnancesurvey.co.uk/oswebsite/gps/information/coordinatesyst
> emsinfo/guidecontents/guide6.html
> 
> For example, today its June 8, 2010, which is the 
> 159th day of the year, so expressed in decimal years
> it is today 2010 + 159/365 = 2010.44.  So deltatime
> would be 2010.44 - 1989.0 = 21.44.  
> 
> I believe ITRS2005 can be regarded as equivalent to 
> WGS84 with centimeter accuracy (although I am a bit
> out of my depth here).  If so, the datum shift can 
> be interpreted as going from from WGS84 to ETRS89, 
> and in Proj.4 we want to express it in the opposite
> direction.  So we reverse all signs.  (The Ordnance 
> Survey uses the same rotation sign convention as
> Proj.4, so that is one worry less.)
> 
> So, as an accurate datum shift for ETRS89, we get 
> 
>   +towgs84=-0.056,-0.048,0.037, < -0.000054 * 21.44 >, < -0.000518 *
> 21.44 >, < 0.000781 * 21.44 >, 0
> 
> or 
> 
>   +towgs84=-0.056,-0.048,0.037,-0.00115776,-0.01110592,0.01674464,0

I have tried that. I now get the following. The Ref lines are the data I
have been provided. The Calc line is what I get with the statement
above. It was an improvement. 
                                 
PATAIAS:                                      
        Ref:    Latitude:   39.6871677778 Longitude:   -9.0025450000 Altitude:      0.000
        Ref:    Easting:       -74582.612 Northing:         2460.852 Altitude:      0.000
        Calc:   Easting:       -74583.114 Northing:         2460.470 Altitude:      0.012    0.631 meters from Ref
        Inv:    Latitude:   39.6871712662 Longitude:   -9.0025391909 Altitude:     -0.691                         
        Diff:               -0.0000034884              -0.0000058091                0.691                         

BARROCAL 2:
        Ref:    Latitude:   40.7508825000 Longitude:   -7.1747969444 Altitude:      0.000
        Ref:    Easting:        80930.409 Northing:       120655.780 Altitude:      0.000
        Calc:   Easting:        80930.751 Northing:       120654.564 Altitude:      0.012    1.263 meters from Ref
        Inv:    Latitude:   40.7508934786 Longitude:   -7.1748008314 Altitude:     -0.705                         
        Diff:               -0.0000109786               0.0000038870                0.705                         

BATEL:
        Ref:    Latitude:   38.7409769444 Longitude:   -8.9387027778 Altitude:      0.000
        Ref:    Easting:       -70039.439 Northing:      -102638.301 Altitude:      0.000
        Calc:   Easting:       -70040.321 Northing:      -102638.468 Altitude:      0.013    0.897 meters from Ref
        Inv:    Latitude:   38.7409785180 Longitude:   -8.9386926531 Altitude:     -0.750                         
        Diff:               -0.0000015735              -0.0000101246                0.750                         

CASCALHEIRA:
        Ref:    Latitude:   38.6597175000 Longitude:   -8.4014394444 Altitude:      0.000
        Ref:    Easting:       -23355.156 Northing:      -111932.822 Altitude:      0.000
        Calc:   Easting:       -23355.845 Northing:      -111933.048 Altitude:      0.014    0.725 meters from Ref
        Inv:    Latitude:   38.6597195517 Longitude:   -8.4014315342 Altitude:     -0.778                         
        Diff:               -0.0000020517              -0.0000079102                0.778                         

CRASTA ALTA:
        Ref:    Latitude:   39.9583455556 Longitude:   -8.8866494444 Altitude:      0.000
        Ref:    Easting:       -64387.200 Northing:        32480.388 Altitude:      0.000
        Calc:   Easting:       -64387.527 Northing:        32480.218 Altitude:      0.012    0.368 meters from Ref
        Inv:    Latitude:   39.9583471081 Longitude:   -8.8866456341 Altitude:     -0.680                         
        Diff:               -0.0000015525              -0.0000038104                0.680                         

FANADIA:
        Ref:    Latitude:   39.3653083333 Longitude:   -9.0732191667 Altitude:      0.000
        Ref:    Easting:       -81019.923 Northing:       -33212.510 Altitude:      0.000
        Calc:   Easting:       -81019.052 Northing:       -33213.931 Altitude:      0.012    1.667 meters from Ref
        Inv:    Latitude:   39.3653210517 Longitude:   -9.0732294452 Altitude:     -0.707                         
        Diff:               -0.0000127183               0.0000102785                0.707                         

MARCO GRANDE:
        Ref:    Latitude:   39.1389694444 Longitude:   -9.3360900000 Altitude:      0.000
        Ref:    Easting:      -104009.123 Northing:       -58072.988 Altitude:      0.000
        Calc:   Easting:      -104007.727 Northing:       -58074.495 Altitude:      0.012    2.054 meters from Ref
        Inv:    Latitude:   39.1389828464 Longitude:   -9.3361063738 Altitude:     -0.709                         
        Diff:               -0.0000134020               0.0000163738                0.709                         

NASCE ÁGUA:
        Ref:    Latitude:   39.2484761111 Longitude:   -7.2524100000 Altitude:      0.000
        Ref:    Easting:        76024.744 Northing:       -46237.481 Altitude:      0.000
        Calc:   Easting:        76024.440 Northing:       -46236.723 Altitude:      0.014    0.817 meters from Ref
        Inv:    Latitude:   39.2484692585 Longitude:   -7.2524065676 Altitude:     -0.792                         
        Diff:                0.0000068526              -0.0000034324                0.792                         

SALMANHA:
        Ref:    Latitude:   40.1534963889 Longitude:   -8.8332422222 Altitude:      0.000
        Ref:    Easting:       -59653.458 Northing:        54112.120 Altitude:      0.000
        Calc:   Easting:       -59653.634 Northing:        54112.029 Altitude:      0.012    0.198 meters from Ref
        Inv:    Latitude:   40.1534972202 Longitude:   -8.8332401686 Altitude:     -0.671                         
        Diff:               -0.0000008313              -0.0000020536                0.671                         

SANTA CRUZ:
        Ref:    Latitude:   41.6743830556 Longitude:   -8.3312663889 Altitude:      0.000
        Ref:    Easting:       -16498.151 Northing:       222796.720 Altitude:      0.000
        Calc:   Easting:       -16501.304 Northing:       222793.861 Altitude:      0.010    4.256 meters from Ref
        Inv:    Latitude:   41.6744088589 Longitude:   -8.3312286018 Altitude:     -0.601                         
        Diff:               -0.0000258033              -0.0000377871                0.601                         

These are the calculations with +towgs84=0,0,0,0,0,0,0:

PATAIAS:                                                                                                                                               
        Ref:    Latitude:   39.6871677778 Longitude:   -9.0025450000 Altitude:      0.000                                                              
        Ref:    Easting:       -74582.612 Northing:         2460.852 Altitude:      0.000                                                              
        Calc:   Easting:       -74582.779 Northing:         2460.870 Altitude:      0.000    0.168 meters from Ref                                     
        Inv:    Latitude:   39.6871676346 Longitude:   -9.0025430513 Altitude:      0.000                                                              
        Diff:                0.0000001432              -0.0000019487                0.000                                                              

BARROCAL 2:
        Ref:    Latitude:   40.7508825000 Longitude:   -7.1747969444 Altitude:      0.000
        Ref:    Easting:        80930.409 Northing:       120655.780 Altitude:      0.000
        Calc:   Easting:        80931.080 Northing:       120654.973 Altitude:      0.000    1.049 meters from Ref
        Inv:    Latitude:   40.7508898317 Longitude:   -7.1748047793 Altitude:      0.000                         
        Diff:               -0.0000073317               0.0000078348                0.000                         

BATEL:
        Ref:    Latitude:   38.7409769444 Longitude:   -8.9387027778 Altitude:      0.000
        Ref:    Easting:       -70039.439 Northing:      -102638.301 Altitude:      0.000
        Calc:   Easting:       -70039.980 Northing:      -102638.068 Altitude:      0.000    0.589 meters from Ref
        Inv:    Latitude:   38.7409748871 Longitude:   -8.9386965301 Altitude:      0.000                         
        Diff:                0.0000020573              -0.0000062476                0.000                         

CASCALHEIRA:
        Ref:    Latitude:   38.6597175000 Longitude:   -8.4014394444 Altitude:      0.000
        Ref:    Easting:       -23355.156 Northing:      -111932.822 Altitude:      0.000
        Calc:   Easting:       -23355.504 Northing:      -111932.645 Altitude:      0.000    0.390 meters from Ref
        Inv:    Latitude:   38.6597159166 Longitude:   -8.4014354406 Altitude:      0.000                         
        Diff:                0.0000015834              -0.0000040039                0.000                         

CRASTA ALTA:
        Ref:    Latitude:   39.9583455556 Longitude:   -8.8866494444 Altitude:      0.000
        Ref:    Easting:       -64387.200 Northing:        32480.388 Altitude:      0.000
        Calc:   Easting:       -64387.194 Northing:        32480.619 Altitude:      0.000    0.231 meters from Ref
        Inv:    Latitude:   39.9583434751 Longitude:   -8.8866494969 Altitude:      0.000                         
        Diff:                0.0000020804               0.0000000525                0.000                         

FANADIA:
        Ref:    Latitude:   39.3653083333 Longitude:   -9.0732191667 Altitude:      0.000
        Ref:    Easting:       -81019.923 Northing:       -33212.510 Altitude:      0.000
        Calc:   Easting:       -81018.715 Northing:       -33213.532 Altitude:      0.000    1.582 meters from Ref
        Inv:    Latitude:   39.3653174211 Longitude:   -9.0732333063 Altitude:      0.000                         
        Diff:               -0.0000090877               0.0000141397                0.000                         

MARCO GRANDE:
        Ref:    Latitude:   39.1389694444 Longitude:   -9.3360900000 Altitude:      0.000
        Ref:    Easting:      -104009.123 Northing:       -58072.988 Altitude:      0.000
        Calc:   Easting:      -104007.389 Northing:       -58074.096 Altitude:      0.000    2.058 meters from Ref
        Inv:    Latitude:   39.1389792184 Longitude:   -9.3361102241 Altitude:      0.000                         
        Diff:               -0.0000097740               0.0000202241                0.000                         

NASCE ÁGUA:
        Ref:    Latitude:   39.2484761111 Longitude:   -7.2524100000 Altitude:      0.000
        Ref:    Easting:        76024.744 Northing:       -46237.481 Altitude:      0.000
        Calc:   Easting:        76024.778 Northing:       -46236.315 Altitude:      0.000    1.166 meters from Ref
        Inv:    Latitude:   39.2484656142 Longitude:   -7.2524105282 Altitude:      0.000                         
        Diff:                0.0000104969               0.0000005282                0.000                         

SALMANHA:
        Ref:    Latitude:   40.1534963889 Longitude:   -8.8332422222 Altitude:      0.000
        Ref:    Easting:       -59653.458 Northing:        54112.120 Altitude:      0.000
        Calc:   Easting:       -59653.301 Northing:        54112.430 Altitude:      0.000    0.347 meters from Ref
        Inv:    Latitude:   40.1534935866 Longitude:   -8.8332440316 Altitude:      0.000                         
        Diff:                0.0000028023               0.0000018094                0.000                         

SANTA CRUZ:
        Ref:    Latitude:   41.6743830556 Longitude:   -8.3312663889 Altitude:      0.000
        Ref:    Easting:       -16498.151 Northing:       222796.720 Altitude:      0.000
        Calc:   Easting:       -16500.981 Northing:       222794.265 Altitude:      0.000    3.747 meters from Ref
        Inv:    Latitude:   41.6744052195 Longitude:   -8.3312324714 Altitude:      0.000                         
        Diff:               -0.0000221639              -0.0000339175                0.000   


> At least today.  
> 
> There may be more recent versions of this kind of 
> transformation.  I believe they are known as 
> "14 parameter transformations" in general.  
> Also, there may be regional versions that are 
> more accurate for Portugal.

I am wondering if this is the case. I have not been successful getting
this information. I think the software they use is a black box to them,
and so they do not know where to look to find the settings they really
use. Sigh...

> 
> Disclaimer: I am not a geodesist, and I haven't
> tested this datum shift on any real data. 
> 
> Mikael Rittri
> Carmenta AB
> Sweden
> www.carmenta.com
> 
> -----Original Message-----
> From: proj-bounces at lists.maptools.org
> [mailto:proj-bounces at lists.maptools.org] On Behalf Of Roger Oberholtzer
> Sent: Monday, June 07, 2010 1:38 PM
> To: PROJ.4 and general Projections Discussions
> Subject: Re: [Proj] TM06 for Portugal
> 
> (full text at
> http://lists.maptools.org/pipermail/proj/2010-June/005233.html )
> 

-- 
Roger Oberholtzer

OPQ Systems / Ramböll RST

Ramböll Sverige AB
Krukmakargatan 21
P.O. Box 17009
SE-104 62 Stockholm, Sweden

Office: Int +46 10-615 60 20
Mobile: Int +46 70-815 1696




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