Bruce Small, post: 418060, member: 1201 wrote: Same rover rod, same rod height. Nothing changed, except obviously something went wrong.
You may not have changed the rod height but the entered value may have changed. I'd certainly be looking at it, anyhow.
Mark Mayer, post: 418091, member: 424 wrote: You may not have changed the rod height but the entered value may have changed. I'd certainly be looking at it, anyhow.
You are correct, but surely I would have noticed because I pay attention to the screen.
For what it is worth, all of the points I checked this morning were correct for N&E, so the stakeout was right on the north rim, etc., but the elevation was off.
Gene Kooper: You nailed it. That was the problem. It was July 1st last year so the heat did it. Ha.
Sounds to me like the rod slipped after shooting the control.
vertical is always the worst, you always prepare for the worst, set up checks, pay attention and still have a blunder. 😡
I'm curious about the standard 5.60 rod height. How did you come to that? I know you don't do things without thinking about them.
Andy J, post: 418253, member: 44 wrote: I'm curious about the standard 5.60 rod height. How did you come to that? I know you don't do things without thinking about them.
5.60 feet puts it about at forehead level, which is a comfortable rover antenna level for me (I use a slide pole 99% of the time). That number is the default in the collector, and I always start off with that number on the rod, with the numbers facing me.. Always. I am obsessive about keeping track of the rod height even on horizontal control just so I won't forget on a topo.
I now recall that once (just once) some ten years ago I had the elevations jump while I was doing a topo, but since it was 800 feet I noticed it immediately. The horizontals did not change, just the elevations, same as this time. I had the standard 5.60 feet on the rover display but the elevations were wacko. I reset the base and was back to normal. Scary, huh.
I am looking forward to hearing what you discover from your aha moment in the shower once you have let this go.
Have you looked through the raw data file yet?
I know you say you notice things on the screen, but my guess is this one time you didn't. I have no new input except my money is that the equipment either changed the rod height on you for some odd reason or the rod was at the wrong height and you didn't notice. Our GPS pole has 3 distinct setting it goes to with a button type system. You could have it in the wrong hole but I normally have it at 2 meters, the next notch down is down at eye level. This of course still leaves a chance to get it wrong but less likely. You might consider one of these poles as you are less likely to get it wrong.
I have been thinking about what could be the problem with this for the last half hour. And, I am at a loss. Nothing to me makes sense with this. And, not that familiar with the Leica world. Going back to what someone suggested, were you using the same routine for the control points shot with the bipod? And, a different one for the Topo shots? If so, perhaps it is a setting in there. Wrong Rover type selected, so antenna phase center was way off kilter?
When I used a sliding type prism pole, I had holes drilled into it at my standard working heights. So, I can use an alternate pin in those holes, to guarantee it wouldn't slip. Very handy when walking through heavy brush. Also (Hindsight being 20/20), when working on a topo, I would often reshoot IP"s and control points, every time I went by one. Not uncommon to shoot the same points about 15 times in one afternoon. This allowed me to "check" my data, and if an error occurred to isolate it to a certain time. Only had to use it once, but allowed me to fix about 20 shots in the office, rather then driving two hours back to to the job site.
Control points and topo shots are exactly the same routine except for control points I use a bipod and shoot five times, using the average, while most topo shots I remove the bipod and take one shot. The exception would be a manhole rim where I take two or three shots and use the average (and note the manhole rim on this project is out the same amount as the other shots). I believe in keeping it simple and following the same routine day after day. Nothing can go wrong that way, right?
I still have not had that aha moment.
Bruce Small, post: 418260, member: 1201 wrote: 5.60 feet puts it about at forehead level, which is a comfortable rover antenna level for me (I use a slide pole 99% of the time). That number is the default in the collector, and I always start off with that number on the rod, with the numbers facing me.. Always. I am obsessive about keeping track of the rod height even on horizontal control just so I won't forget on a topo.
I now recall that once (just once) some ten years ago I had the elevations jump while I was doing a topo, but since it was 800 feet I noticed it immediately. The horizontals did not change, just the elevations, same as this time. I had the standard 5.60 feet on the rover display but the elevations were wacko. I reset the base and was back to normal. Scary, huh.
I keep mine at 6.50 so it's just over my head and the my noggin won't make the robot lose tracking. 😉
Given the expressed attention to measure up detail and input of data and the fact the RL shots check, the most probable source of the error would be a slip in the physical rod height when the bipod was removed. At least that is where I'd start my investigation.
Leica antenna vertical offset? I've been bitten before by the "Leica 1202 Tripod" vs "Leica 1202 Pole" antenna designations because the former assumes that you use the Leica tribrach puck with custom height hook and adds about a foot.
One other possibility that is worth considering is depending on what instrument you are using, I've witnessed some of the newer instruments locking onto the rod just below the prism and still getting an EDM result for distance. Some of my guys complained about locking on to random shiny things, so I tested it and sure enough I was able to duplicate this issue, for multiple instruments. They have created updated firmware to reduce their sensitivity, but still does it sometimes....
Anyways, just a thought, but your vertical error sounds close to what I remember.
Brian Gillooly, post: 418389, member: 12268 wrote: depending on what instrument you are using
In Bruce's case it was GPS, so robotic lock isn't the issue.
Jim Frame, post: 418398, member: 10 wrote: In Bruce's case it was GPS, so robotic lock isn't the issue.
I should have read more carefully! but still something for everyone else to look out for 🙂
For GPS I would guess something happened to what receiver was chosen or distance to phase center settings from bottom of mount. Possibly there is a quick release option similar to Topcon that got checked.
I response to the above regarding rod slip, I see that sometimes, but always tell my crews to use a height where you can use that little bar to go through the pole or use a fixed height rod.
Bruce,
Could it be a software bug?
What is the measurement difference between your rovers slant height and vertical height?
Do you use separate software routine for control vs topo? Some apps have precise measurements option with averaging for control, then a quick routine for topo.
Could the control points have been measured with a vertical height, while the topo used a slant height?
deus ex machina
