dear all,
i would like to know that
1.how i can calculate a new mini prism constant with my leica ts02?
2. when i had finished my survey work i have rechecked with my back sight point, but is always changing my backsight coordinate value.
why its happening?
please give me suggestions.
thanks
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Replies
The reason for this issue is significant temperature changes and your instrument station has been drifted.This may caused due to drift of your instrument station but also possible drifting of your back sight.for example if you did station setup by 9 o'clock in the morning and when you check back sight after 10.30 oclock the temperature might differ by 5-10 C. That gives significant drift and the difference is depend on how long your back sight is.If your back sight is more than 50 m you may experience significant erro but is not bigger than 4mm. as Best practice we always need to use thermometer in order to check the ambient temperature of starting time of the survey and also,allow sufficient time to climatise the instrument before do the station setup or resection or what ever method. and also if you take more than one hour of the survey in one station,you may check your back sight every half and hour to make sure you are not drifted and observe if temperature has not been significantly changed.
Regarding prism constant,You may precisely measure prism constant buy three peg test.The ideal thing is if you measure perms constant for one prism using one instrument that prism constant is no longer valid for another instrument even though same brand of instrument. Each instrument has different laser frequency and therefore prism and instrument need to be coupled always.
The prism constant cannot be determined precisely except in a laboratory. If you know the brand and model of your prism, someone might be able to help you.