I'm fairly new to the robotic world and we recently purchased a used S5 Trimble.?ÿ We have also been renting a S5 unit for several weeks but its not the same unit we purchased.?ÿ
With the unit we had been renting we normally set up back site with the typical Chicago Steel Tape -30mm prism on a tribrach.?ÿ Then we shoot the Multitrack Trimble prism.?ÿ When ever it auto locks on the CST prism it always appears to be a little left of the actual center of the prism, maybe 0.01' or a little less but enough you can see its not centered.?ÿ It appears to center up on the Trimble prism.?ÿ In my mind there is a slight error involved in this.?ÿ Not enough to worry in most cases but maybe enough when doing a boundary or building layout.?ÿ It seems to me if always shooting a CST prism the error would cancel but if back sighting a CST and then shooting the multitrack there would be some angular error.
I brought this up with our dealer and got kind of a vague don't worry about it, that's normal answer.?ÿ This was with the rental I have yet to test the robot we actually purchased, I just got it last week.?ÿ Is there a test for this??ÿ An adjustment??ÿ I plan to maybe turn some angles carefully with a regular total station and then compare that to what the robot gets.?ÿ
I know that the visual sighting often looks "off" but as long as the instrument knows what prism you're pointing at , it?ÿ "should" be compensating for the difference.?ÿ ?ÿ Since you're using two different prism brands, I would be worried as well.
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Dave, take your shots in both faces and compare your angles.
Chr.
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The instrument will sight the prism off center when tracking, it adjusts the horiz and vert reading accordingly.?ÿ?ÿ
That's normal. You can reassure yourself by noting down the angles it is reading to the prism, then substituting a conventional prism and reading the angles yourself. I would agree that is a bit disconcerting when you first notice this. (Of course, it is possible that it is out of adjustment - but the test just described will tell you).
Leica's robots have a similar feature. When a customer calls me with this question I have them do the below to show how the system works.
I have them put the instrument in manual mode and aim as accurately as they can to the center of the prism and write down the Hz and V angle. Then we put instrument into self pointing and move it off the prism and initiate the measurement. Then compare the Hz and V angle. This will tell you if your instrument calculates the center of the prism.?ÿ
I just went outside.?ÿ We got back a Nikon total station that was repaired and I set it up and put some mag spikes in the ground and measured a set of?ÿ 2 D-R angles, all to CST prisms.?ÿ I then set up the robot and did the same thing, and let it do its own thing through the data collector.?ÿ It measured within 1 second of what the Nikon did, but this was to the same CST prisms.?ÿ I think switched out the CST prism on the fore sight to the Multitrack prism.?ÿ This changed the angle by about 9 seconds.?ÿ Same distance.
Turning to the Multitrack I could not turn sets, the data collector will let me switch target types, but not in the middle of a set of angle, so I just shot the multitrack several times.?ÿ Since I was shooting a CST backsite I couldn't figure out a work around to this. ?ÿ It was pretty much the same every time, about 9 to 10 seconds of difference on the angle.?ÿ
The distances from the instrument to the back sight and fore sight were pretty short, a little less than 200 feet so 9 seconds in that distance amounted to 0.009 feet.?ÿ As far as I'm concerned very little?ÿerror.?ÿ Not a very scientific test?ÿbut just a quick check to make sure the distances and angles were good on both machines.
As I mentioned above we had been renting an S5 and what I did today was with the S5 we purchased.?ÿ Just visually, it appeared to line up better with the cross hairs of the S5 when auto locked on the CST prisms.?ÿ Overall pretty happy with the results and put my mind at ease.
BTW, thanks for the answers.?ÿ I'm one of those people that just doesn't trust think kind of technology without proving it out to myself.
I wouldn't use the multitrack to turn any rounds or for control purposes.?ÿ The offset is to the prism, but if the multitrack prism isn't line up, you are introducing additional errors.
"When using the Trimble MultiTrack 1000 the
prism mode selection has a crucial impact on the
horizontal and vertical angle variations. Although,
the active prism mode is more robust in a high
reflective environment, it significantly degrades the
accuracy of the vertical angle measurements."
Interesting article although a little too deep for me.?ÿ I know the salesman said to set up the target to be semi active, which seems like good advice.
While the article is mostly related to Leica, the chart shows that you'll continually have a horizontal error of +2/-5 mm error with the multi-track prisms.?ÿ If you are using trimble i would suggest getting the trimble traverse kit (not the seco knockoff) to minimize angular errors for control.
I don't even want to know what the Trimble traverse kit costs.?ÿ Probably thousands.?ÿ I have about 6 tribrachs and the CST prisms that I can use.?ÿ I'm not sure why these wouldn't work.
Another check is to toggle "AutoLock".?ÿ If the collimation (that is the difference you're seeing) is correctly set the crosshairs will return to the center.?ÿ Turn it back on and it should jump back off center like you've noticed.
BTW traverse kits are the bomb and well worth the $$$
Looks like the traverse kits are $1000 or more for a single setup.?ÿ I can probably get by with the prisms and Sokkia tribrachs?ÿ I have now.
The robot and data collector are setup for autolock now.?ÿ All I have to do is get the gun close to the target and it locks on. Doesn't matter if it the old prism or the trimble one, as long as I have the correct one selected on the data collector.
Hey mate,
?ÿ ?ÿ ?ÿ ?ÿ ?ÿ ?ÿ ?ÿ You may want to check the your Sokkia tribrachs to confirm that they are suitable for robotic use. Robots tend to have much more aggressive turning forces than conventional instruments and require tribrachs that are rated with a higher torsional stiffness than standard tribrachs.
As for prisms, I've found as long as you adopt the right prism constant everything should be sweet, I'm currently using Leica traverse kits with an S6 and getting unreal closures.
