What is the smallest angle recommended to shoot them? 90 degree being the ideal , 0 degrees being no good.
Do you shoot them in DR (reflectorless mode) or standard prism mode with zero offset?
Thanks in advance
It all depends! you need to check out the type of target you are going to use with your instrument.
Set up your normal prism on a tribrach about 10 metres away and measure the distance. Place a flat card across the to of the tribrach and mark the centre.
Now stick a reflective target to a block of wood, angle bracket, or similar and place it on the centre mark. Check the reading.
Rotate the target 10 degrees and repeat. Continue to do so until you cannot get a reading; do the same in the opposite direction.
You now have a table of results which will tell you what sort of error you will get at any angle (ON THE FLAT).
If you are going to be observing significant vertical angles repeat the procedure to a target on, say, the next floor in a stairwell.
You only need to do this once and you then have certainty (and proof for others) that your readings will be accurate.
If you are going to
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Do you shoot them in DR (reflectorless mode) or standard prism mode with zero offset?
If you have time try the test out in both reflectorless and standard prism mode.
You might find from the results that there is a small "prism" constant to apply for each type.
I normally only switch to reflectorless if I can't get the range on standard prism mode, which will depend on what instrument you are using. The angle of incidence at which you can get a return signal drops off quite quickly once the vertical angle is significant.
surely the constant for reflective tape is zero?
It's nominally zero, but there's always going to be some offset. With good quality reflective tape it should be close enough to zero to be irrelevant.
Hey mate,
?ÿ?ÿ?ÿ?ÿ?ÿ?ÿ?ÿ?ÿ?ÿ?ÿ?ÿ?ÿ?ÿ I use reflectorless for tape targets with Trimble instruments, I assume that's what you are using considering you stated DR. The prism constant of zero is what should be adopted for tape targets, when I used to use a Leica 1200+ it had a specific tape target setting pre-installed in the prism selection list. The prism constant and results were identical to when I tested it with reflectorless mode.
As stated above, unless you're chasing sub-millimeter accuracy a zero constant is fine.?ÿ
Many thanks
How far off the perpendicular do people normally shoot reflective targets?
Its not practical to have the instrument at 90 degrees to all targets.
If you do the test I suggested at the beginning, you will know how far off perpendicular your particular instrument can measure before you can no longer get a signal.
Shooting targets to resect your location.
Apply prismatic tape to a short pole that can be seen from all directions.
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Yesterday we bought some "stick-on" targets. I have not seen them. But, they were placed on a concrete wall and the SX10 would not shoot them in prism mode (EDM Timeout), only in reflectorless mode, even though we were close to being straight on. I don't know if they were not the right kind, but I was somewhat disappointed they would not work as a prism. I was not there yesterday, but I will be there this afternoon
There's a 45 degree zone that works reliably, each side 22.5 degrees off the line perpendicular to the face of the target.?ÿ
Not reflective tape
Get prismstic reflective tape.
I got some reflexite tape.?ÿ Just finished doing some tests. When you're 45 degrees of the target the results are hit and miss. When your within 25 degrees off perpendicular to the target the results are repeatable.
Many thanks for all your advice.
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Yesterday we bought some "stick-on" targets. I have not seen them. But, they were placed on a concrete wall and the SX10 would not shoot them in prism mode (EDM Timeout), only in reflectorless mode, even though we were close to being straight on.
At what distance?
I don??t know what your using them for but I like to use shallow angle ones for angle only in resections.
Yesterday we bought some "stick-on" targets. I have not seen them. But, they were placed on a concrete wall and the SX10 would not shoot them in prism mode (EDM Timeout), only in reflectorless mode, even though we were close to being straight on.
At what distance?
If you are intending to use these over an extended period of time, once you have worked out the maximum distance reduce it by a third - to allow for all the muck which will collect on the surface over the months. Otherwise you will find you can't get readings you used to get without problems.
I was advised by my Leica tech to always do a 2 face reading when shooting reflectorless due to possible minor missalignments of the laser beam with the scope. It cancels out the errors by averaging the distances. I have seen 7mm differences between face1 and face 2 when the angle is about 30 degrees at about 100m distance, even with the instrument recently calibrated. I am using a 1" Leica TPS 1200 .