Which is the best precise mini prism I am using one but all the time when I traverse its gives me 8mm diffrence if some one know appreciate
The first prism assembly purchased from EBAY would register 0.035 ft shorter than any other prism assembly I had.
Upon close examination, a couple of spacers had been put behind the prism mounting.
Removed them and all was good.
There are some mini prism (and others) that just don't have a 0mm or -30mm feature.
A few makers use some odd builtin correction offset for their own line of equipment.
I like make a tribrac & tripod setup and rotate all my prisms to record a comparison.
You will need to call them to see where to purchase as they are only manufacture and do not have retail department.
😉
Depending on how i use the mini prism mine has an offset = 0 or 30 mm.
But mounted in this little frame the offset is 8 mm!
Chr.
Interesting, I have the same frame, for hooking it to a plumb bob string and I have a choice of -30mm or 0mm.
where is the 8mm at?
-JD-
I believe you will find the difference is between the basic specs of the manufacturer of you differing instruments.
along the back, such as if you held it up against a wall. You can take the prism itself out of the frame and the point =0mm I believe.
That's very good I have same frame and I can use that thanks
Here is a instruction sheet for the mini prisms that I use. I hope it is helpful. Pay close attention to the location of where your string goes through the holder/frame. That may account for the 8mm error you are experiencing.
Peanu Prism Instruction Sheet PDF
I hope this is helpful
Jimmy
YOINK :good: :good: :good:
Thanks yes it's very helpful
Indeed, when you screw the prism in the frame the back of the prism is 8 mm from the back of the frame. I used it that way to monitor points marked on a quay in the port.
For monitoring I always preferred to remove it from the frame. Using the point on the back allows for some side-to-side angular movement without introducing additional error.
When the prism is in the frame, if you are not exactly 90 from what you are observing, you can add extra error.
yes sight the point first then introduce the prism and direct the chainman to line it so it's facing you (as best you tell).
need a good chainman for this.
Aloha, great post! Much appreciated by beginners like me!:good:
Thanks very good reply i appricate
here is what we use, from seco (5216-00). I have been using this for deformation surveys for almost 9 years now. Also great for a lot of other work. The HI is 0.100 m. We put a extra sensitive bubble on there, although since it is so short it has to be outside the circle to start to matter much. Easily swivels 180°. Takes about 20 to 30 seconds to get it accurately centered. Works best on smooth surface like asphalt or concrete. Real nice when you have 100 or more points to shoot on a concrete dam.
John,
had not seen this one before! Looks high tech ... does it weight enough for windy conditions?
And one more question, do you use the autolock for monitoring jobs? Did you ever compare results with and without autolock?
Chr.
Chris: t is not real heavy. Easy to carry. Never had a problem with it in the wind, but I probably never used it in real high winds.
We have an S6 high accuracy model. I believe the autolock is better than manual. More consistent. Way faster too. Since we try to shoot all points at least twice, ideally from setups 90 degrees apart, we depend more on the distances than the angles, although it is all adjusted together (GEOLAB).
I have done tests on my network here at home comparing the S6 with mini (autolock) prism versus a T2 and a T3 with glass wild targets. I will post results of that one of these days soon.
