Best Reflectorless

Look for smallest beam and longest range.

Beam size directly affects accuracy when the angle of incidence is low. Imagine the size of a flashlight beam on a wall when shining perpendicular to the wall. Now imagine the beam when shining down the wall. The distance the reflection of the perpendicular beam travels is nearly the same anywhere in the beam. The distance the reflection travels in the low angle beam depends greatly upon what part of the beam the light is in. The edm has to determine a distance from the return signal. Smaller beams have less variability than wide ones. It's been a few years since I have worked with lots of different total stations, but the Sokkia SRX robot had a fantastic reflectorless edm.

Range is important also, not so much because you plan to use your edm to measure power poles a half mile away, but because the more powerful edm will allow you to get shots on less reflective objects at normal ranges more reliably.

I could not improve on Shawn Billings post above. He is spot on.

Shawn Billings, post: 349134, member: 6521 wrote: Look for smallest beam and longest range.

In that order too. Smallest FIRST, then long range.

Back "in the day" I bought one, I bought a Leica. Because it had a very narrow beam. But, it was not very long range. (It's still not very long!) But, it can shoot over 1000' feet to a 1" x 2" piece of reflector tape.

To make a problem free Narrow Beam, Reflectorless gun, the mfr has a bit of of a problem. You HAVE to make the beam, and cross hairs concentric. And, IF you make the beam wider, then you don't have to build into the gun, a mechanism to USER adjust the EDM, to hit the right spot.
So, to get a narrow beam gun to work at a great distance, you may have to occasionally adjust the alignment of the EDM. Mine has just that adjustment. I remember Topcon was touting it's WIDE beam gun, because it was nearly impossible to knock the EDM off of alignment... so it was a trouble free gun.... That's not the solution I want to use. Shop hard, and meddle with it.

A way to test this, is to set up the gun, about 150' from a flat wall. Then, drive a wood stake, about 5' closer to the gun. Place a finish nail on the wood stake. Then, change to all different kinds of targets on the stake. IF it misses the target, and gives the dist to the wall... you can immediately tell it.
The Leica I got, LOVES Dpt of Transportation Tape. It's the stuff that goes on signs. And comes in 2" rolls, for 18 wheelers. So, Mine is hard to fool. It grabs that DOT tape very well.
I'm sure that there is a better test, especially for a LONG range one.
But, That was the one we used.

If you don't mind, post back and tell us what you buy. (I still like running reflectorless!)

N

Look for smallest beam

I have never seen this in any total station specifications. Is it available somewhere as I would be interested in differences between total stations.

Shawn Billings, post: 349134, member: 6521 wrote: Look for smallest beam and longest range.

I have never seen this in any total station specifications. Is it available somewhere as I would be interested in differences between total stations.

Some of them did provide specs on beam divergence at some specified distance (like 1.5cm at 50m). I don't know that there is an industry standard for it though. If you can evaluate the instrument before buying, you can test it. Set up the instrument some distance (a couple of hundred feet or so) from a building with a precise corner, like a metal building. Preferably have something beyond the building corner, such as another wall. Turn the instrument to the corner and shoot a reflectorless shot. Then slowly turn the instrument away from the corner. Angularly, how far from the corner did the reported distance switch from the building corner to the wall beyond? Was there a point where the distance reported was neither the corner nor the wall beyond?

Next test is to setup a prism pole with a bipod on pavement 50 feet or less from the instrument where you can see the prism and the pole tip. Shoot the prism normally. Then turn the instrument to the pole tip and slightly to the side. Shoot the pavement reflectorlessly. How do the distances compare?

My comment is about the dc software. Trimble TBC/Access includes a "Shoot a Round Object" offset function (reflectorless distance to face of object, turn angle to edge, radius calc'd and added to distance - you get coordinate of center of object), that works great with reflectorless shots. Spectra Precision Survey Pro has no such function. Which is a big drawback to using reflectorless effectively to tie poles, tres, signs, and such.

As I recall, Leica had an ad one time that included a piece of card stock with a hole in it, about half an inch or so in diameter and asked people to see how their reflectorless instruments compared to the Leica. So you set the card up at some distance and shoot through the hole to an object beyond the card. Move the card further back and see at what point you no longer get the distance to the object, but get the card (or some average of the two). This was quite a few years ago. One thing about this test though, is that beam cross-sections aren't always circular. Some of them are more elliptical, longer in one axis than the other.

In Access there is now a choice of methods. The new one requires angle observations to both edges of the circular object. It then bisects them and takes a reflectorless distance. Point is stored at the calculated centre and radius is stored as a note.

Based purely on personal experience with Leica, Topcon, Sokkia, Nikon, and Spectra, I'd go with a Leica unless you use a Trimble data collector.

I've only experienced a Nikon, but that was before Trimble got hold of them.
I didn't buy it, but was amazed at the way it worked.
The rep lined up the edge of a door in the crosshairs and focused on that and read.
Then without moving the instrument focused past the door onto a distant object and read to that.
Repeated and reread with same results.
The Nikon would read (measure) to what was focussed on, not in sight

I'd want a live demo and in varying situations.
Preferably wet and dry, but that might be hard to organise.

Reflectorless is one the big weaknesses of Trimble's S6.

You need an absolutely clear line of sight to the target.

It will tend to grab the nearest thing in the viewfinder regardless of where the crosshairs or visible laser are pointing.

Shooting through fences or vegetation is dodgy at best.

I'd rate it about 3 / 10

There are at least 3 DR types on the S6 though. (different options and editions) Some are better than others. I think on the whole Leica have always had the best (narrowest) though.

Prismatic Reflective tape has enabled prisimless instruments to excede their factory specs many times.
When I can find a had worth of holding a plumb bob, I will take most of my shots that way and he doesn't have to carry around half the toolbox.

If I have to access the point and apply tape to it why would I shoot it reflectorless? Kind of defeats the purpose if you ask me. I generally use that feature for inaccessible measurements. I can see if you are trying to pick up wall lines or something using the tape maybe...

Dan, it's a sure fire way to be sure, when you use reflectorless, and it is useful, if you don't have a real strong laser, for long distance shots.
The argument you make, is significant. There is a place for the idea that you really need it right.... so tape does this.

N

I don't know if other software does this but survey pro you can shoot two flat walls or one wall and an angle to the corner. I find that eliminates a lot of reflector less issues

I have a Topcon GTP 3000 with a long range laser. Out to 3600 feet. I bought it for the reflectorless. I was working a FIMA project in 2010 after a ice storm. My task was to map the existing OHP lines. This was in the Missouri Delta farm land. Flat and wide open. I ran GPS baselines at the beginning and end of each circuit. Baselines were +/- a half mile long. I set my prism constant profile to the center of the average width of a power pole. I'd setup on the first GPS control point as Harold set the back sight bipod. Then Harold would set the foresight bipod a half mile ahead. I'd start shooting power poles as Harold when back to pickup the back sight. By the time Harold got to me I've shot a mile of power poles. I would be packed and ready to load in the truck. Same thing on the next setup. My back sight was already set. And as I was setting up Harold was setting a back sight a half mile ahead. Then going back to get the back sight as I was shooting poles ahead. I was shooting from 2500 feet to 3000 feet of power poles every setup. I'd check radial stake outs on the first couple of poles where I started and ended the leg. I was blowed away as we were checking within a few hundreds on each power pole. We were averaging about 3 and a half mile of power line an hour with very good accuracy. We were very cost-efficient on that project. Granted we were not looking for elevations on the project. But it would have been easy enough to have Harold with a staple gun staple dots 5 foot high on every pole. As it was he was on the move all day long. That was a cool project.