I don't know if anyone has had an issue like this before or has any solutions short of new equipment. Back in October, while laying out curb, we into a problem with the grades we were getting from our Topcon GPT 8205A Robotic. We checked one of our first hubs and the cut/fill was way off. We checked quite a few others and our benchmark with inconsistent results. The next day we broke out the level and shot all the hubs. If I had to guess, we had about 5 out of 50 that were off over a 0.10'. We sent the gun in to get calibrated and explained the issue to the service personnel. Fast forward to today. Something didn't feel right so I checked into a hub/tack and shot it 8 times. 4 elevations are within .01' of each other. Compared to them, the other 4 come in as follows: -0.03, +0.06, -0.51 and -0.50. Horizontally, the distance from the gun is good but the angles are all over the place. I wouldn't be able to put 3 of them into a .06' circle. I didn't have the bipod attached so I expected some difference, but the 2 furthest points are almost 0.5' apart.
Set the gun up back at the office shooting almost 50 shots with a bipod, without a bipod, moving some then coming back and don't get anything like I did this morning. The first time the service guy said he had never heard of anything like that. We didn't send it again, yet. I half expect when we do it will work fine and they'll say there's nothing wrong. Has this ever happened to anyone else, and if so, what was the problem?
Was your crew wearing anything reflection? Sometimes the instrument will lock onto a safety vest that has reflective material on it instead of the prism.
I had nothing on it would pick up. Had it happen once and never again. My closest glows with all the color in there but we can usually explain why we don't have vest on and get by with the blaze orange or safety yellow shirts. I can draw a best fit line through the shots and none are more than 0.008' off. Our last gun, a Topcon 800 lost the ability to hold a horizontal angle a couple years ago. I'm afraid this may be the start of that.
Could it be your tripod, maybe the legs slip, or the screw that mounts to the instrument could be worn out.
PA PLS, post: 412314, member: 9658 wrote: I don't know if anyone has had an issue like this before or has any solutions short of new equipment. Back in October, while laying out curb, we into a problem with the grades we were getting from our Topcon GPT 8205A Robotic. We checked one of our first hubs and the cut/fill was way off. We checked quite a few others and our benchmark with inconsistent results. The next day we broke out the level and shot all the hubs. If I had to guess, we had about 5 out of 50 that were off over a 0.10'. We sent the gun in to get calibrated and explained the issue to the service personnel. Fast forward to today. Something didn't feel right so I checked into a hub/tack and shot it 8 times. 4 elevations are within .01' of each other. Compared to them, the other 4 come in as follows: -0.03, +0.06, -0.51 and -0.50. Horizontally, the distance from the gun is good but the angles are all over the place. I wouldn't be able to put 3 of them into a .06' circle. I didn't have the bipod attached so I expected some difference, but the 2 furthest points are almost 0.5' apart.
Set the gun up back at the office shooting almost 50 shots with a bipod, without a bipod, moving some then coming back and don't get anything like I did this morning. The first time the service guy said he had never heard of anything like that. We didn't send it again, yet. I half expect when we do it will work fine and they'll say there's nothing wrong. Has this ever happened to anyone else, and if so, what was the problem?
Was there anything reflective, glass, shimmer from dew soaked grass in the distance? I had a hell of a time 5-6 years back with and older robot (TCA1100) locking onto window panes or being distracted by car window glares.
I've seen the safety vest be an issue with those old robots. Another thing could be mirrored or reflective sunglasses
I had the same problem with an 8203. I ruled out all of the suggestions listed above, and still had the problem. So I carefully watched the how the robot was tracking a stationary prism through the eyepiece. The crosshairs were moving in a small circle around the center of the prism. But randomly the circle would grow to about 0.5' of vertical radius. We had the unit serviced a few times and it helped, but it never locked to the center of the prism again. The crosshairs would still drift around about 0.02'. I'm convinced that Topcon's tracking technology of that era does not hold up with age. The same thing happened to an APL1A, and both robots were always handled with the utmost care. We have moved on to Focus robots and never looked back.
Were you shooting into the sun? Sounds like a track issue, shooting into the sunlight early in the morning or late in the afternoon is problematic.
Thanks for the insight. AdamWest, that seems to be exactly what we're dealing with. I can watch the data in stakeout mode and get left and right distances all over the place as well as the cut. We just had it in in October and I don't like the thought of having it in every few months to make sure we can trust it. I was told August was the earliest we could get new equipment. The other guy on the crew is going to go nuts with all the double checking we are going to do until then.
Where was the sun when the problems were happening? I know that early models of the Leica robot had problems when looking into a sun which was low on the horizon.
For everyone that replied, I had pretty much considered everything you had brought up. The sky was overcast with now sun. Behind me were trees for the most part and nothing reflective. The distances worked out well so it was on the prism. I wore nothing reflective. I believe the tracking is out of whack and may or may not work properly on any given day, with a job coming up requesting 6" contours because of the lack of grade changes. For now, we send it in and double check the bejeesus out of everything shot robotically.
