Hi everyone I am using topcon 360 prism with topcon rebotic total station Gpt 8003 most of the time I find 10 to 13 mm diffrence in stake out I want to know what is the best prism for the layout and why is this error come if any one know I appreciate thanks
> Hi everyone I am using topcon 360 prism with topcon rebotic total station Gpt 8003 most of the time I find 10 to 13 mm diffrence in stake out I want to know what is the best prism for the layout and why is this error come if any one know I appreciate thanks
I would suggest that you define a short baseline (less than one 30 m tape length) and test against your taped value. Try adjusting your taped distance to temperature and pull. Then shoot shots at the prism in a variety of rotational increments around the 360. There may also be a constant in the instrument that got played with. I recall the older Topcon instruments having an instrument constant (not prism constant) easily accessible and alterable.
About the best prism question, I personnaly prefer to layout with a single face mini prism tilted and aimed at the instrument. Not too sure what your problem could be, I'd start with testing against tape baseline.
The A6 prism you have use 6 small prism with a 0mm offset, but when the instrument sights between prisms, there is a void between the two. In this void the instrument must choose one, and it can be 15mm difference. This is why the 9000 series Topcon went to the A7 triangle 360 prism with 2mm offset, and now to the ATP1 with 7mm offset.
When using the A6 you will need to point one prism directly at instrument.
Or you can purchase the ATP1 with 7mm offset, amd triangular prisms.
Lee Green
Great answers above. I have experienced this also on short shots. If I only have a couple to set, I cover the prism with my hands so only the one straight at the gun is showing to confirm it is giving me the correct distance.
