We've had occasional issues with Carlson grabbing a backsight height or some other HI previously entered, and putting said height in the topo mode screen. Definitely one that has bit us...
The only superior evidence is that which you haven't yet found.
Wild guess here... in your op you described the site as a 'parking lot'. Were there lots of vehicles and possible multipath? Not intermittent, which you might have picked up on, but enough to confuse the software on heights only?
leegreen, post: 418433, member: 2332 wrote: 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?
The difference between slant height and vertical height is only 0.02 feet, same routine for control vs. topo except I use a bipod for control stability, and I doubt a software bug. On the other hand, something happened and I am still mystified. Not a clue to what went wrong. One lesson I have learned is to check into the benchmark at the end of the topo. I had not done that as part of the routine before because, obviously, the base is fixed so that "can't" change, and I am super careful when I take the five shots on the bench mark at the start, looking at the rod height and looking at the display to make sure they match.
Bruce Small, post: 418503, member: 1201 wrote: obviously, the base is fixed so that "can't" change
Maybe it was not your base. Perhaps there was a base nearby on the same frequency, with same horizontal position, but different vertical?
Review your raw data.
I'm not sure how you get two bases with the same horizontal??
David Livingstone, post: 418508, member: 431 wrote: I'm not sure how you get two bases with the same horizontal??
If both bases are on SPC, then the horizontal datum should be very close to the same.
If Bruce was getting corrections from a different base, likely the antenna type was different.
We had a bug with one of our data collectors, it would store a distance that at times was hundreds of feet different than the actual measurement. It once said I traversed 0.15'. So I wouldn't be to quick to doubt the bug.
Probably not the case with Leica, but in Trimble SCS900 you can set it to default to different rod heights depending on if you are doing a continuous topo or stopping and taking a shot. Had a grade foreman call me one night when it was raining saying all the grade he had just cut on top of DGA was 6" off, and they were going to start paving the next morning. I knew it wasn't off, had been checked too many times. Said he had checked rod ht, etc, etc. Told him to check a specific spot and while I was waiting for him to call back I remembered that little piece of information.
leegreen, post: 418510, member: 2332 wrote: If both bases are on SPC, then the horizontal datum should be very close to the same.
If Bruce was getting corrections from a different base, likely the antenna type was different.
I've seen that very thing happen, the second base would need to be unnumbered in the DC file. If so it will show up when the DC is downloaded as a point somewhere offsite.
If the second base has a number that's already in the DC file then it will blow up the topo shots and you should see it immediately.
It doesn't matter what projection the second base is on, the DC is only seeing the unprojected numbers the second base is broadcasting, as long as the Lat, Long's are NAD83 (recent epoch), the XY at the topo site will be good.
leegreen, post: 418510, member: 2332 wrote: If both bases are on SPC, then the horizontal datum should be very close to the same.
If Bruce was getting corrections from a different base, likely the antenna type was different.
Had that happen before! I always thought someone should write a little survey book titled "what went wrong". Especially with rtk. Some really quirky things would happen to radios in the old days....I remember noticing my radio would always drop out when I would hear a train horn, picking up another's base.....
Bruce, I always wanted my receiver over my head. When you are measuring with bipod do you walk away and let it measure and then on topo shots without bipod your floppy sun hat might be messing with the signal???? Jp
Good reason to use a base ID. A second base on the same frequency, using the same protocol would be pretty unlikely in my neighborhood but it would be almost impossible to identify without using the base ID, so I use it.
It would probably be worth explaining your process for export/import of the data into you drafting package. Perhaps some of the conversions along the way are the source of the error?
Is it possible the antenna type was changed inadvertently or the 'hook and tape' ghost popped up?
OK, I get it. He might have been picking up a different base on a different points. I read it like someone had a base setup on the same base point Bruce did.
David Livingstone, post: 418610, member: 431 wrote: OK, I get it. He might have been picking up a different base on a different points. I read it like someone had a base setup on the same base point Bruce did.
Yes, my bad. I should have said "they may have been on the same horizontal datum", not horizontal position.
I was having this same problem last week where my rover was trying to pick up a different base, but it gave me a warning when this was happening. It said something like "new base position was detected, do you wish to continue".
I now recall, slowly, some details. For one stretch near a 1-story building I was shooting the sidewalk elevations so I certainly would have run the rod up to 11.6 feet and changed the rod height on the display. Those shots are 0.4 feet low, same as all the others, so it almost certainly was not a matter of me having the wrong rod height on the open shots.
I am convinced something happened in the base to the tune of 0.4 feet (same as ten years ago when the base elevations jumped 800 feet but the horizontals were correct. I was an assumed datum, something like 2000/5000 so it is highly unlikely a different base was involved. It is possible that it was pure coincidence that the jump happened while I was removing the bipod. Nothing in removing or adding a bipod would have any effect. That I've done what, 20,000 times over the years. A few times over the years a different base intruded, but the unit always said something about, "Base coordinates are different than expected."
Lesson learned, the hard way: Doing everything methodically and carefully every time is not sufficient. There is indeed a reason to check into the benchmark as the last shot of the day.
Time to move on. Nothing to see here.
20,000 times over the years? I've told you a million times not to exaggerate. 😎
Bruce Small, post: 418662, member: 1201 wrote: I was an assumed datum, something like 2000/5000 so it is highly unlikely a different base was involved.
Since you are using a message type that includes the base coordinates and the controller compares them, then you are probably right that the different base theory is not the issue. Having said that, assumed coordinate systems would have no impact. The corrections are not based on the projected coordinates system, but are based on ECEF. Even the assumed system has some geodetic relationship (even if somewhat approximate).
Forgive my ignorance of Leica data files, but:
I would think that the information needed to solve the "what happened," and "how to fix it," would be in the RTK "raw" file.
I'm pretty sure that the Trimble .dc, as well as the Carlson Surv-CE .rw5 files contain enough information to dope this out (and probably FIX it).
But Maybe not!
Loyal