9 CHECK AND ADJUSTMENT
9-1
9 CHECK AND ADJUSTMENT
9.1 Checking and Adjusting of Instrument Constant
Note:
Each of the Prism mode and Non-prism mode has instrument constant.
You must obtain the instrument constant of prism mode. If you reset the instrument constant of the
prism mode, you must vary the non-prism constant (Non-prism-short, Non-prism-long) by the same
quantity as the amount of increase or decrease of the instrument constant of the prism mode.
Normally, the instrument constant does not have discrepancy. It is recommended you measure and
compare with an accurately measured distance at a location where the precision is specifically moni-
tored on a consistent basis. If such a location is not available, establish your own base line over 20m
(when purchasing the instrument) and compare with the data measured with newly purchased instru-
ment.
In both cases note that the setup displacement of the instrument position over the point, the prism,
baseline precision, poor collimation, atmospheric correction, and correction for refraction and earth
curvature determine the inspection precision. Please keep in mind these points. Also, when providing
a base line in a building, please note that the difference in temperature greatly changes the length
measured in the building.
If a difference of 5mm or over is the result from the comparative measurement, the following proce-
dure as shown below could be used to change the instrument constant.
1)
Provide point C on a straight line, connecting straight line AB which is almost horizontal and
about 100m long, and measure straight lines AB, AC and BC.
A
C
B
2)
Obtain the instrument constant by repeating 1) above several times.
Instrument constant=AC+BC-AB
3)
When there is error between written instrument constant value and calculated value, review
the Section 9.7 “How to Set the Instrument Constant Value” procedure.
4)
Once again, measure at a calibrated baseline and compare with the instrument base line
the length.
5)
If using above procedure and no difference is found from the instrument constant at the
factory or a difference of over 5mm is found, contact TOPCON or your TOPCON dealer.
9.1.1 Checking of the accuracy of the non-prism mode
If you reset the instrument constant, you must check the accuracy of the non-prism mode.
1)
Set a prism 30 to 50 meter apart from the instrument and measure the distance to the
prism by prism mode.
2)
Take off the prism and set a (white) board.
3)
Change the mode to the non-prism mode and measure the distance to the board.
4)
Repeat above procedure and measure some points.
If the difference of the prism mode and non-prism mode is the range of ±10mm even one time,
the instrument is normal.
If the difference is never the range of ±10mm, contact TOPCON or your TOPCON dealer.
Summary of Contents for GPT-8000 Series
Page 89: ...5 PROGRAM MODES 5 28 ...
Page 124: ...11 SETTING ATMOSPHERIC CORRECTION 11 4 ...
