> Someone posted in the Leica world zero=-34.4mm
Foreigners 😉
I learned this lesson the same way you did, the hard way. This was several years ago, and I believe it was directly responsible for me developing my current "I don't believe you until I do/try/research/learn it for myself" attitude.
I was going on the say-so of someone I thought knew what they were talking about. I have since encountered numerous firms and crews using Leica hardware with a Seco prism glass (not that there's anything wrong with Seco prisms). Roughly 10% (just guessing) knew the exact correct offset to apply, the others had anything from zero (which only creates a 4.4 mm error, but still) some of the others had -30 set!
Yes this will effect the measurements. ATR (Automatic Target Recognition) was designed to find and acquire a prism in a passive mode. There is a white page available on the AT401 unit (Leica's industrial Measuring Total Station) that provides more detailed information.
In short, ATR was designed to find specific prisms quickly and adjust accordingly. If you enable ATR and set the prism correctly, powersearch you will notice the crosshairs slightly offset (upper left quadrant). when you press "ALL/MEAS" or "DIST" the cross hairs will center on the prism....NOTE the Angles will not changes because of the ATR applying the correct offsets for the CORRECT Prism selected. If you do not have the correct prism selected, the wrong offsets will be applied.
Go into Leica Geo Office and change the prism to reflect the correct prism shot and recalc the setup.
Most every prism I??ve ever seen can be changed to have two different constants. ?ÿAnd my guys are like kids in candy stores with new equipment . Even my little peanut can be zero or another offset like 30mm. ?ÿJust set up on a few good tight cp??s and see what it gives you. Also it does not come from factory all set for your particular prism and constant. ?ÿThere are millions to choose from. Most extreme I??ve seen was +50 and -60. Not the same prism. ?ÿTwo different ones on same day
The Leica 0.0mm = -34.4mm thing is frustrating and nonsensical IMO. Ideally, Leica should either state THEIR prism constant equation of 0.0mm = -34.4mm on their glass, or go with the norm.
A couple of years ago we were tying out a number of mon's on I-5 south of Bellingham, and we borrowed a second crew from another office for the evening. The PC had a Topcon gun but Leica glass (we have Leica everything), and I asked him what he had set for a prism constant in his gun. He replied "-30", apparently unaware that Leica glass had a different prism constant. I was able to show in Star*Net that by applying the additional -4.4mm, the results improved quite significantly. He's held -34.4mm ever since as far as I know.
There's just NO need whatsoever for Leica or anyone else, to muddy the waters when precision and accuracy are paramount.
The only superior evidence is that which you haven't yet found.
We did the same thing, years ago.?ÿ I was a fairly young party chief and believed it when they told me what the offset was.?ÿ Funny thing is we laid out more than a few major large buildings and additions using the -30mm os, and the steel all went up and fit together fine.?ÿ
> I know they are both 0mm constant, so should be okay, but I am not 100% sure.
They're not the same. I put together this graphic to help me manage my prisms:
I'm not seeing the graphic??ÿ How are they not the same if both "0"?
https://surveyequipment.com/assets/index/download/id/51/
?ÿ
The Leica 0.0mm = -34.4mm thing is frustrating and nonsensical IMO. Ideally, Leica should either state THEIR prism constant equation of 0.0mm = -34.4mm on their glass, or go with the norm.
A couple of years ago we were tying out a number of mon's on I-5 south of Bellingham, and we borrowed a second crew from another office for the evening. The PC had a Topcon gun but Leica glass (we have Leica everything), and I asked him what he had set for a prism constant in his gun. He replied "-30", apparently unaware that Leica glass had a different prism constant. I was able to show in Star*Net that by applying the additional -4.4mm, the results improved quite significantly. He's held -34.4mm ever since as far as I know.
There's just NO need whatsoever for Leica or anyone else, to muddy the waters when precision and accuracy are paramount.
I agree, but there's a fun little history lesson here - if what I was told is correct.?ÿ Story was related to me that everyone "copied Wild's tribrach" design so that things would be interchangeable.?ÿ Then later the tilting prism was somewhat generically adopted to match the vertical offset of the old top-mount EDMs.?ÿ Since everything tended to gravitate towards interchangeability - Wild declared their prism constant of -34.4mm to be "zero" becuause it directly offset the EDM constant (because of it being mounted and/or machined in such a way that it was a +34.4mm constant).
Other manufacturers, probably rightly so, determined that EDM technology would change - and that using the absolute constant was the preferable route.?ÿ Both make sense depending on the viewpoint, but this is why there's always been two versions of offsets for Leica glass.
> I know they are both 0mm constant, so should be okay, but I am not 100% sure.
They're not the same. I put together this graphic to help me manage my prisms:
I'm not seeing the graphic??ÿ How are they not the same if both "0"?
https://surveyequipment.com/assets/index/download/id/51/
?ÿ
Funny, nevermind.?ÿ I just realized this a pretty old thread!?ÿ Probably got lost in an update.
I'm fairly new to robotics, with that said, is it poor practice to use a circular prism (large or small) while using a robot??ÿ I'm not concerned about distance offsets,?ÿ I'm concerned with angular error due to pointing at different prisms.?ÿ I have used a circular prism as a BS and a 360 on a FS to turn sets just because I only own one 360 prism.?ÿ The BS prism is always pointing directly at the robot.?ÿ Will the robot not center in on the prism correctly even if the correct prism is set??ÿ
I can only speak to Trimble or Leica.?ÿ Leica has a very accurate 360 prism if you take care to orient the yellow triangle back towards the instrument (it's looking at you, but used to align like a sight).?ÿ The larger circular prisms are better for all robotics as long as they're good quality prisms & pointed correctly.?ÿ Some even have aiming sights (like on some traverse sets).?ÿ The Trimble 360 prism is the least accurate of the bunch, but is till capable of tight work if you take effort to point on entire peice of glass back at the robot.?ÿ The passive 360 has an odd number of prisms, the active has an even number - so you can use a divider between the prisms as a "sight" on the passive one, and on of the prisms themselves as a "sight" on the active one.?ÿ The new MT1000 prism (disco ball thing) is supposed to be more accurate by default.?ÿ If you're dealing with a lot of slope none of the 360's are all that great.?ÿ If pointing accuracy becomes a major concern, say for tight control or layout, invest in a nodal prism.?ÿ They usually have a weird constant, but there is no error intruduced by pointing.
I haven't used a brand new Leica much, I know they actually don't turn to center - only apply a calculated offset.?ÿ I think prism pointing would still affect performance, though.