Gibraltar

1997, 3 identical points

7 Parameter Helmert Transformation,
 |X|   |X|    |Tx|   |  0  -Rz   Ry |   |X|       |X|
 |Y| = |Y| +  |Ty| + | Rz   0   -Rx | * |Y| + D * |Y|
 |Z|   |Z|    |Tz|   |-Ry   Rx    0 |   |Z|       |Z|
    T     S                                S         S

T          ... Target Datum 
S          ... Source Datum 
Tx, Ty, Tz ... geocentric X/Y/Z translations  [m]
Rx Ry, Rz  ... rotations around X/Y/Z axis    [radian]
D          ... correction of scale            [ppm]

see
Boucher, C., Altamimi, Z. (1992): The EUREF Terrestrial 
Reference System and its First Realizations. 
Veröffentlichungen der Bayerischen Kommission für die 
Internationale Erdmessung, Heft 52, München 1992, pages 
205-213 (1) 

REMARKS: in (1) correction of scale D is included in the 
rotation matrix 

******************* Attention *******************
In some transformation applications a different formula 
than the formula above could be in use. The signs and order 
of the rotation parameters are then define differently and 
rotation unit can be arcseconds. For test purposes you can 
find in this information system verification data to check 
your application to get correct results. 
 
Distinguish the following cases:
a) change of signs of rotation (Coordinate Frame Rotation)
   Rx = -Rx
   Ry = -Ry
   Rz = -Rz

b) change of signs and order of rotation 
   Rx = -Rz
   Ry = -Ry
   Rz = -Rx
******************* Attention *******************

Although there is a large scale and orientation error, the 
small area of Gibraltar makes a 3 parameter shift 
accceptable at 1 m accuracy. Otherwise very large shifts 
and rotations will result.