1.10 Survey of 34mVLBI Antenna Reference Point

(1) Survey method

1) In 1999, the survey of the
reference point of 34m VLBI antenna was conducted through the same gindirect
methodh applied in 1998 survey.

2) The indirect method applied here
was a method to set a survey target near the reference point of VLBI antenna
and measure this target with TS from base points located on two sides of VLBI
antenna. From each of the base point, a total of nine positions of the target
have been measured by rotating the azimuth angle and elevation angle of VLBI
antenna respectively to three different directions. As a result, coordinates of
the target at 18 different positions on a spherical surface have been gained.
And from these coordinates, the coordinates of the spherical center (reference
point) of VLBI antenna were estimated by applying the method of least squares.

3) For controlling the change of
direction of the survey target whenever the azimuth angle and the angle of
elevation of VLBI antenna have been shifted, remote radio-controlled method was
used in 1999 instead of the manual method applied in the previous year (1998).
Apparently, this new method brought significant improvement in terms of higher
safety of the surveyors and better efficiency of their work.

(2) Survey results

1) As displayed in Table 19, the
estimated coordinates of the spherical center (reference point) by applying the
method of least squares to the eighteen (18) coordinate values gained in 1999
survey showed evidently that the reference point was appropriately determined.

Table 19 Results of
the calculation of the spherical center using the method of least squares

Maximum value of the
residual (mm) |
Standard deviation of the
spherical center (mm) |
||||

X |
Y |
H |
SD |
SD |
SD |

0.9 |
0.8 |
0.7 |
0.2 |
0.3 |
0.3 |

2) As compared in Table 20, the
discrepancy between the coordinates of VLBI antenna reference point gained in
1999 survey and those gained in 1998 survey was insignificantly small.

Table
20 Discrepancy resulting
from the comparison with the coordinates of VLBI antenna reference point gained
in 1998 and in 1999

Year |
N (mm) |
E (mm) |
U (mm) |

1998 |
-1.1 |
0.6 |
0.7 |