I have a Topcon gpt8205 robot with an A3 360 prism. Everytime I checked the tracking in the past I am sure it centred on the pole if two prisms were facing the instrument. It now seems to only center on one of the prisms and not the pole as in the past. Am I mistaken that in should center on the pole?
It has just been calibrated.
My Topcon Robot always seems to be just to the upper right or upper left (I cannot remember), of dead center of the prism. It is controlled by the collimation procedures when it is adjusted on a regular basis at the shop.
Jimmy Cleveland, post: 355337, member: 91 wrote: My Topcon Robot always seems to be just to the upper right or upper left (I cannot remember), of dead center of the prism. It is controlled by the collimation procedures when it is adjusted on a regular basis at the shop.
But does that not mean that the angle of measurement is out if the prism is turned slightly away from the robot? I am sure it centered on the pole before but want to be sure before I send it back.
I don't think it's possible for it to center on the pole given this prism arrangement.
If you need it accurate you must make sure one of the prisms is directly facing the instrument.
Totalsurv, post: 355323, member: 8202 wrote: I have a Topcon gpt8205 robot with an A3 360 prism. Everytime I checked the tracking in the past I am sure it centred on the pole if two prisms were facing the instrument. It now seems to only center on one of the prisms and not the pole as in the past. Am I mistaken that in should center on the pole?
It has just been calibrated.
?
If you remove the prism what will it center on? Probably your safety vest.
To the best of my knowledge the pole has no other means to tell the instrument where it is.
Our Trimbles lock above and left of center. If you manually sight the pole and set zero, then turn on autolock and the angle should not change. The instrument automatically adjusts the values when auto tracking
The gun can't track the center of the pole. For more accurate measurements, you need to put marks on the top and bottom of that prism directly over the center of each piece of glass. Those marks help you point the center of glass directly at the gun.
Try using a nodal point prism like this:
http://www.surveying.com/Products/Prisms-and-Assemblies/25-mm-Prisms-and-Assemblies/6405-12-FOR
vern, post: 355368, member: 3436 wrote: If you remove the prism what will it center on? Probably your safety vest.
To the best of my knowledge the pole has no other means to tell the instrument where it is.
Ok I never said it tracks the pole. If two prisms were in view of the robot it would center between the two of them on the prism shown above. I guess I am looking for someone with the same setup to confirm.
Michael wicks, post: 355365, member: 10847 wrote: ?
??
I don't know how all the technical stuff/robotic adjustments work. I know the robot is designed to accept the corrections between the camera/tracking mechanism and the optical line of sight that Troy checks when he services and calibrates it.
All that robotic technical stuff is kinda confusing, but I know that I can run some super tight traverses with my robot, and have been for over 8 years without incident. I have done enough to know that whatever it is doing behind the scenes, it is working.
FYI, my robot is a 2002 model Topcon GPT 8005A.
Jimmy Cleveland, post: 355408, member: 91 wrote: I don't know how all the technical stuff/robotic adjustments work. I know the robot is designed to accept the corrections between the camera/tracking mechanism and the optical line of sight that Troy checks when he services and calibrates it.
All that robotic technical stuff is kinda confusing, but I know that I can run some super tight traverses with my robot, and have been for over 8 years without incident. I have done enough to know that whatever it is doing behind the scenes, it is working.
FYI, my robot is a 2002 model Topcon GPT 8005A.
Thanks. On mine which is pretty much the same setup it locks dead center on one of the prisms if two are facing even though this would be at an different angle from the pole center. I guess it must automatically adjust in the instrument but I was sure it centered between the two before.
Totalsurv, post: 355323, member: 8202 wrote: I have a Topcon gpt8205 robot with an A3 360 prism. Everytime I checked the tracking in the past I am sure it centred on the pole if two prisms were facing the instrument. It now seems to only center on one of the prisms and not the pole as in the past. Am I mistaken that in should center on the pole?
It has just been calibrated.
I have used the same prism, and if you watch through the gun, while having someone slowly turn the prism, you will likely see what I saw:
It locks on a single prism. As it turns, it tracks the prism, when it loses one, or the return from another becomes greater, it will snap to the new prism. This is minute, but noticeable when doing precision work.
The gun may never exactly center on the prism, it doesn't matter, since it does the same offset centering on the backsight, but this is NOT the phenomenon that you are experiencing.
The Leica 360 prism has a much different design, but the same issue. Leica resolves this will a yellow arrow that is to be orientated with the instrument, allowing the user to align the sighting location with the center of the pole, relative to the instrument.
dmyhill, post: 355424, member: 1137 wrote: The Leica 360 prism has a much different design, but the same issue.
I'm under the impression that the Leica arrow is for vertical only, and that the horizontal is unaffected by prism orientation.
Jim Frame, post: 355426, member: 10 wrote: I'm under the impression that the Leica arrow is for vertical only, and that the horizontal is unaffected by prism orientation.
I guess it doesn't define it here...(from a newsletter, http://www.leica-geosystems.us/downloads123/zz/accessory/accessories/newsletters/Accessory_1_360Prism_en.pdf )
[INDENT]1. GRZ4 PROFESSIONAL 360å¼ REFLECTOR
This reflector is recommended for all robotic
work performed with a survey pole. The rubber
mountings on the top and bottom of the prisms
provide protection of the glass if the pole falls
over. The reflector is supplied in a padded
case for safe transportation.
The GRZ4 has an overall pointing accuracy of
5mm. However, when aiming directly at one of
the three prisms, indicated by yellow arrows,
an accuracy of better than 2mm can be
achieved. [/INDENT]
I don't know what axis it is speaking of, but simply says an overall pointing accuracy. Again, this is easily tested...
dmyhill, post: 355585, member: 1137 wrote: Again, this is easily tested
Agreed, but I've never seen the point in doing so. The only time I use the GRZ4 is when I have a lot of dirt shots to take at considerable distance, and control is already in place. That means it stays in the truck almost all the time; I think I used it once last year. Most days I use the GMP101 miniprism, which is way smaller and lighter than the GRZ4 and has a 1 mm pointing error spec. I lose lock more often than with the 360, but I can run control intermixed with topo and my arm is happier at the end of the day.
Totalsurv, post: 355323, member: 8202 wrote: I have a Topcon gpt8205 robot with an A3 360 prism. Everytime I checked the tracking in the past I am sure it centred on the pole if two prisms were facing the instrument. It now seems to only center on one of the prisms and not the pole as in the past. Am I mistaken that in should center on the pole?
It has just been calibrated.
I have used the this prism for years. The center of the prism where it screws onto the pole is what it tracks to.
Look at the gun while someone slowly turns it and it should stay at same angle.
You can adjust the scope to match the robot. I do this a couple times a year or always use the tracking to zero the backsight.
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Scott McLain, post: 355733, member: 6271 wrote: I have used the this prism for years. The center of the prism where it screws onto the pole is what it tracks to.
Look at the gun while someone slowly turns it and it should stay at same angle.
You can adjust the scope to match the robot. I do this a couple times a year or always use the tracking to zero the backsight.Sent from my SAMSUNG-SGH-I747 using Tapatalk
Yes thanks for confirming that. The problem with mine is that it is a different angle as it turns and locks to the next prism. It is as I suspected, back to the shop it goes or is it easy to adjust, I have the manual but it is badly translated into English?
Totalsurv, post: 355743, member: 8202 wrote: Yes thanks for confirming that. The problem with mine is that it is a different angle as it turns and locks to the next prism. It is as I suspected, back to the shop it goes or have you ever adjusted it yourself?
Sorry I did not think this through. If you are very close, like 20 feet. It will jump from one to the other. At this distance I can get it to go about 0.03 off true center. This error will get less as the distance increases. If I am doing stake out at less than 50 feet from gun, I put my hands over the prisms on the side for an instant to make sure it has the center.
Only other solution is the A7 prism that has the triangle shape.
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