Any of you construction surveyors have any experience with either Trimble or Topcon machine control on an asphalt paver? We have a project where an existing 2 lane is being widened on the north side to become 4 lanes with a suicide lane in the center. So one side is all new construction, most of the other is overlay of the existing pavement. Road runs east-west, so the new CL and crown will be 7' north of the existing north edge of pavement. The overlay will vary from maybe 3" deep at the old CL to 1' deep at the existing north EP. This varies because the existing pavement has been there awhile and is up and down, and we have a smooth profile to meet. So we have a need to be able to control the screed to get to grade rather than using a certain depth as is the normal case.
We've looked at both systems. Topcon uses a combination of GPS for location and fan lasers (with a 30' vertical range I think)for grade. Minimum of 2 lasers are used so they can be leapfrogged ahead as they go out of range, the more the better. They recommend control points set every 250', lasers are mounted on 2m tripods on every other control point. There is a laser receiver/GPS rover mounted on each side of the paver. The model controls the grade on each side. Also have a laser receiver/rover and controller on a rod to check grade with. The say they can use one of our Trimble bases, so won't need a new base. As I understand the procedure, you would begin by setting a laser up 250' ahead of the starting point, and use the rover to check the 2 CP 250' either side of that. The 2nd laser is set 500' ahead of that one, checked the same way. Paver starts up and when it gets to 500', it switches to the 2nd laser. Then the first one is leapfrogged ahead another 500'.
Trimble uses robots for their system. A prism is mounted on one side of the paver, and a slope sensor controls the cross slope on the first pass. The prism side of that pass would be matched on the next pass. Since one robot can only follow one prism, it requires a minimum of 3 robots to be able to leapfrog 2 robots and have another one to check grade. Control is set 800 ' apart, can free station or set up on control with robots. Can go 400' either side of the instrument before switching to the next one.
All our earthwork machine control and GPS is Trimble. The Trimble system is quite a bit more expensive than the Topcon, because of the need for 3 robots. However, it looks to me like it's a lot less labor intensive. I think either one is going to require a man dedicated to moving systems and checking grade. We may be able to rent some or all of it, just trying to decide which would work the best. Looking for input from anybody that's used either one for pros and cons.
Was in Vegas all last week for Con-Expo and got to see all the equipment on display. That's some show. Of course, Trimble says Topcon doesn't work well, and Topcon says Trimble doesn't either.
Topcon and Trimble both work.
The Topcon mmGPS is much better for larger open sites, since the laser is self leveling, and you get longer distances between control points, than you would with trig leveling from a Robot. If the site has many overhead obstructions, such as buildings and trees, then the Robot setup Trimble or Topcon will work better.
I've setup Topcon Millimeter GPS on pavers for many projects. I also own a Topcon mmGPS system.
Some of your information is a little off track. The mmGPS Transmitter can be 1000ft from the receiver or a maximum of 2000ft apart from one transmitter to the next transmitter. I recommend control points for the transmitters have very tight vertical elevation and span every 500ft to 750ft. This way your maximum distance from transmitter to receiver is 250ft to 375ft. Also you can operate with only one Transmitter if you want, but the system can use up to 4 transmitters on a site, at the same time to span longer distances.
The transmitters look like a laser level, they do have a fan beam to cover 30ft elevation change, as you said. So with 4 transmitters at there maximum, you could span 8000ft horizontal, and 120ft vertical change. But for best results I would cut those maximum distances in half. Topcon can also operate with the Robot setup using same software and most of the same hardware (swap receivers fro prisms), they call this LPS, like the Trimble system.
Also you can still get results from GPS only, on Topcon mmGPS system, when the receivers can not see the transmitters. You will loose the needed high vertical accuracy with GPS only elevations. I have set these up many times on airports and running tracks mostly, where specs require 1/4" or less on paved surfaces.
When setup properly, and with good control, it works great.
Lee Green
Thanks for the info, Lee. Those distance were quoted from the Topcon guru that stopped by the office. They wanted a CP in between to have a check that was closer than 500' from the laser.
The guy at Vegas recommended having a couple of extra tripods so the moves ahead would be faster. When running full speed, they may be getting 30'/minute, so I think it would keep one guy hopping to stay ahead of them.
The Trimble guy pointed out that Topcon depends on 2 systems working (GPS and laser) at the same time. I could see some potential for problems if the GPS were to go down (for whatever reason) with 20 loads of asphalt sitting in front of the paver.
Additional checks can be good, but not need if you have good level run. These intermediate check points can be just a nail. For the control points that the transmitters will be setup on, we use a wood treated 6"x6"x10ft with a 5/8" all thread in the top, set 3-4ft in the ground. If there will be multiple pavement lifts, and passes, this is much faster. Just screw transmitter on and go, no leveling need, no problems with sun and legs heating up.
Lee Green
Typical sales men, trying to sell you extra 2m tripods at $750 each.
Use 6x6 post, cheaper and more stable.
We save cost atimes by renting more Transmitter.
Trimble vs Topcon, Two Systems Versus Even More For Trimble
Topcon is using two well tried systems and they interact.
Each Trimble robot is a separate system, not sure how they interact.
30' feet per minute is optimum speed. I would not worry about paving time lost to reset survey control equipment as flagmen and traffic control devices also need to be reset periodically.
I don't believe that 1 foot of paving, it is totally out of specs to place that much asphalt in 1 layer. The sub grade should be well established before paving. Even that 3" overlay should be placed as a 2" base course and a 1" finish course.
Paul in PA, PE, PLS
Trimble vs Topcon, Two Systems Versus Even More For Trimble
Of course, none of the lifts will be over 5" loose, but they may be 1" on one side and 5" on the other. Multiple lifts, varying depths. Trimble has a way to adjust the file so the depths are increased by whatever the rolldown percentage is to help with that, not sure Topcon does that.
The crews did about 30 miles of Interstate, all 4 lanes, last year and averaged 30'/minute, so that's a given.
Also, the box on the paver with the Trimble system is the same box we use on the dozers, so would have that available. The robots don't interact with each other at all, just switch the paver box from one to the other.
Setting 6x6 posts every 500 ft. on a 4 mile job will be a job in itself. I never use wood unless it's only going to be used immediately. Sun and rain here will warp them pretty quickly. I usually use 3" galvanized pipe with a 5/8" bolt clamped to the top. If the ground is solid, can just drive them in with a sledge hammer. If not, dig a hole and set in Quikcrete. I like the fact that the total stations could be moved around and not limited to being set on a control point, because you never know what's going to be in the way. May have to switch from one side of the road to the other. The new lane will be built first, with traffic maintained on the overlay side. Then it gets switched. There will be places where the control points on one side probably won't be good for paving on the other side, think fills and traffic. The ability to move the transits around would be helpful.
Hopefully somebody that's used the Trimble system will chime in and point out the pros/cons they've seen. I'm not paying for either one, but the guy that is is looking for recommendations. I know who will get the questions if unforeseen problems pop up.
Trimble vs Topcon, Two Systems Versus Even More For Trimble
Both systems are efficient. Just remember that a total station trying to track a prism in direct line of sight with the sun is no fun. Consider this when you do your control planning (It appears you already made your choice).
Also, if a station becomes ineffective, the contractor maybe tempted to say "let's track from the other station" which could be a little far for reliable trig leveling. What is the accuracy of the robots that you plan to use?
Me personally, if the crew is indeed running at 30'/minute and if skies are open, I would go with GNSS/Level technology. If equipment is new and back-up available (as it would with both choices), I don't see much issues.
Trimble vs Topcon, Two Systems Versus Even More For Trimble
Instrument would be the 1 second gun shown here.
Trimble vs Topcon, Two Systems Versus Even More For Trimble
I have only seen videos showing both systems in action so I can't speak directly to that. But in your area I would have to go with Trimble due to the service and support. On a system like that that requires multiple parts to be functioning flawlessly, I would want to be sure there were folks around who could provide on site assistance if necessary. And what I've heard from other KY contractors is that the topcon guys are trying to cover the state with five guys and support is severely lacking. Just my .02. Let us know how you decide!
Trimble vs Topcon, Two Systems Versus Even More For Trimble
It looks like we are going to see the Trimble system in action in a couple of weeks at the Corvette test track being built across I65 from the Corvette Museum in Bowling Green.
@leegreen I would agree on your point. Both will do since both of them are quality asphalt for paving.
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Ron
