ashtech DG14, Справочное руководство

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Coordinate Transformation 81
Coordinate T
ransformation
The generic formula used to translate and rotate from coordinate system 1 to
coordinate system 2 is as follows:
where
e
rx
=
e
x
expressed in radians, similarly for
e
ry
and
e
rz
.
Example: Define local datum as the WGS-72 datum
Send the following commands to the receiver:
$PASHS,UDD, 0,6378135.0, 298.26,0,0,4.5,0,0,-0.554,0.23
$PASHS,DTM,UDD
This implements the transformations listed in Table 5.2 and below.
D
x=
D
y=0
D
z= 4.5 meters
m= 0.23 x 10
-6
e
x
=
e
y
=0
e
z
= –2.686 x 10
-6
radians = –0. ” 554
in the following equation:
After issuing the $PASHS,DTM,UDD command, the receiver internally transforms
positions from the reference datum (WGS-84) to the user-defined datum. In
standard text books, however, the datum transformations are given from local
datums to WGS-84. To simplify entering the transformation parameters, the
translation, rotation, and scale parameters are defined from the local datum to
WGS-84.
Table 5.2. Ellipsoid Parameters for WGS-72 and WGS-84
Datum
Reference
Ellipsoid
a[m] 1/f
WGS-72 WGS-72 6378135.0 298.26
WGS-84 WGS-84 6378137.0 298.257223563
x
y
z 2
D x
D
y
D
z
1 m
6 –
´
10 +
( )
1
e
rz
e
ry
–
e
rz
– 1
e
rx
e
ry
e
rx
– 1
x
y
z 1
+ =
x
y
z WGS84 0
0
4.5
1 0.23
6 –
´
10 +
( )
1 2.686 –
6 –
´
10 0
2.686
6 –
´
10 1 0
0 0 1
x
y
z 1WGS72
+ =