just reduce it all to the vertical difference, run it backwards and forwards like a checkbook and the error should jump out.
:good:
This is what I do when carrying elevations on a control traverse. Note the vertical delta direct and reverse on the foresight, mean the two assuming they agree within +/-0.03', plus up the HI, add or subtract the vertical delta, minus out the HR to get the new elevation, on the fly and into the book. As a general rule, don't go beyond 500'. Do a vertical back sight check. If they don't agree, rinse and repeat. It's much easier to repeat a setup or get a new measure up than it is to wade through reams of raw data files looking for the proverbial needle in the haystack or having to run the traverse over again. If the vertical deltas direct and reverse don't agree fairly close, that would point to a collimation issue with the instrument. A bad measure up will jump up and b*tch slap you. 😀
In my opinion, there is something to be said for recording level loops and control in field books. They can be scanned, archived and used later for the next project.
Where I work, we can search a database by township, range, section and pull up the notes from a deformation survey performed last year just as easily as a road survey performed 110 years ago.
I hardly can imagine being able to do that with a .rw5 file or proprietary software.
imaudigger, post: 333421, member: 7286 wrote: Not familiar with the Carlson format. I always handle the control data myself and only allow Carlson to reduce radial data.
Are you sighting the correct crosshair in the scope? (I'm sure you are, but I have seen problems in the past).
The only other place to look would be the instrument height or the distance. It appears that when you swap target and gun you have the same measure up?I suspect the distance. I would at the min. tape a baseline and shoot the distance in traverse mode and see what it records. Almost seems like a scale factor issue.
Personally I like to survey on the ground and convert my data to grid later to avoid issues with scale factors.
Some funky data you have going on there.
Yes to the cross hair in the scope...There's only one. Yes to the same prism and scope height at each setup.
Regarding scale factor:
In SurvCE (or at least the second line of the .rw5 file above), it says the scale factor is 1.0000... But in the Data Collector, in "Job Settings", "System", there is a line called "Projection", which is set to "USA/NAD83/VT". I don't think it's scaling the data, but there's no "None" shown as an option. Could this be a factor (pun not intended)?
Kris Morgan, post: 333392, member: 29 wrote: Couple of quick thoughts. When you level your instrument, rotate the barrell and watch the horizontal angle. If it moves more than 10", then you need to colminate the instrument, but that ONLY affects horizontal noticabley.
For the vertical, EVERY time we do anything where elevations are critical, then the rod is verified as reading correctly in the morning, noon, and at the end of the day. Takes about 1 minute and catches ALL kinds of problems and helps ISOLATE problems when you find one.
Also, depending on your scale, since it's scaling distances, then over time, it will affect the elevations.
However, unless your scale is 0.999, that shouldn't amount to a 0.8' in half a mile so I'd say it's in the rod and HI. For this reason, the rod is set at a certain rod height, say 5.5 feet, and the markups are double checked.
Kris:
Imaudigger was suggesting distances, not angles might be at the root of the issue. I thought the Scale Factor was 1.0 (see second line in file), but when I looked at the project settings in SurvCE, it says the projection is USA/NAD83/VT. If I click "edit projection list", choose that projection to edit, here's what it's telling me:
Projection: Transverse Mercator
Datum: NAD83
Scale factor: .99996429
Central Meridian: -72.5
Lat. of Origin: 42.5
False Northing: 0 m
False Easting: 500000 m
Doesn't this suggest that EVERYTHING I've collected with this DC since I started using it, has been on GRID, not ground?:excruciating::excruciating::excruciating:
Your Raw Data is just that. Pure, as observed data, uncorrected for scale factors. Or it should be otherwise it's not Raw Data.
SurvCe takes your Raw Data as you record your observations, reduces slope to horizontal and calculates coordinates (ENZ, NEZ) per your settings.
If a Scale Factor applied, Atmospherics, etc then those coordinated observed points are either Ground or Grid.
Run a Raw Data file through any software and it should notify you whether you are applying Scale Factor or not. You could toggle that On or Off.
Now to observations in TS mode.
Vertical, Elevation errors or disagreements can often be checked by again noting target heights compared to instrument heights on the same set of legs (tripods).
Egs, instrument above top of legs = 265mm, target height above legs 165 mm. Difference of 80 mm.
So one can often deduce what a backsight height should be when a target is swapped for the TS.
I have 2 different target sets with differing heights, but at least I can do quick checks, and recalculate.
Also, with an instrument in Good Adjustment, it's easy to use the forward observations, heights and calculate from observed slope distance and the resultant vertical difference a height of instrument or target.
I nearly always catch a resulting error by such. It can be that easy.
But I can't stress too highly, the need to know your instrument, it's strengths and it's weaknesses, maintain collimation adjustments (I do that before any serious 3D work, even checking daily) and importantly your screws, bolts that hold your legs together from feet to the head not forgetting the clamping.
You soon discover just one return trip could have been avoided by some standard, careful yet easy to perform checks. Call it good house keeping, whatever, it Pays Dividends.
Oops. Make that difference 80mm but from. 265 to 185mm.
(memo to Richard, small screens, big fingers, not best to post from) :-$
Just curious. I know in my jobs with TBC and Trimble Access, if I start a total station job with state plane defined in the job, and told it sf = 1, it will apply a scale factor based on the coordinates even though I started at 5000,5000. I have to use a project setting called totalstation with no coordinate system and sf = 1.
Sent from my SM-T530NU using Tapatalk
Richard, post: 333211, member: 833 wrote:
I assume it has automatic compensators?
I once accidentally turned mine off, and couldn't work out why my verticals were suddenly up the creek!
With regards to instrument /target heights you could just measure up from top of legs.
And the 2015 "Find the Grasshopper's Blunder" award goes to..Richard!😀
I checked the compensators and, sure enough, I had turned them off for some test I was running ages ago and forgot to turn them back on.
I'm thinking that this could definitely contribute to not just this V height bust, but the general inconsistency in my observations recently. Who knows what trying to adjust the V datum or Vertical collimation, without compensation on, would do? I'll do those again before any further field work.
Should I take comfort that my horizontal was only out by .08 even without compensation? I won't go there.
Thanks, all, for the valuable input.
That's excellent.
When my Nikon goes out of level the electronic bubble fires up.
If I relevel then Escape (Esc) all is well, but I can actually turn the compensators off by hitting Enter whilst its out of level which apparently overrides them and suddenly, no compensation.
There are different characters against each component when they are Off.
#Hor means no compensator.
A lesson that cost me a lot of time and money.
I actually sent it off for repairs!
Don't feel bad. I was on a construction site a several years ago. I had people waiting on me, and the robot was acting weird, and would not lock on me for a backsight to save my life. I just about lost my cool, and walked back up to the robot, ready to beat it into submission with the sledgehammer (it had already been a BAD morning). When I got to the robot, I saw that I had failed to remove the lens cap! Yes, I won the dumb a$$ of the day award that day. I needed it. I laughed for a few seconds, calmed down, and went to checking what they needed, and the robot worked just fine.
I would suggest going one step further and actually going through the columniation measurement routine.
I use a Trimble 5600 and to meet the tilt access error distance/angle requirements, I had to utilize a radio station tower for a sight.
There was no other way to get a steep enough angle at the required distance. I know a lot of guys just use a power pole and that probably works too.
Unless your instrument is pretty far out of adjustment, I'm not so sure that having the compensators turned off would induce the type of elevation errors you were getting. Report back and let us know.
imaudigger, post: 333544, member: 7286 wrote: I would suggest going one step further and actually going through the columniation measurement routine.
I use a Trimble 5600 and to meet the tilt access error distance/angle requirements, I had to utilize a radio station tower for a sight.
There was no other way to get a steep enough angle at the required distance. I know a lot of guys just use a power pole and that probably works too.Unless your instrument is pretty far out of adjustment, I'm not so sure that having the compensators turned off would induce the type of elevation errors you were getting. Report back and let us know.
Yes, I'm going to start from scratch, looking at each adjustment. I've just discovered in the manual for this instrument (Topcon GTS255) that there are actually TWO things that can be turned on and off that might be related to this. First, is TILT. That's available from the front panel in normal operation. I had that one off for both X and Y axes.
But I discovered another, found in the Special Mode (Menu Mode) screens called "Systematic Error of Instrument Correction".
They say: "Setting ON/OFF for error correction of collimation and horizontal axis for angle measurement. Note: Perform this item after complete section 17.5 'Adjustment of Compensation Systematic Error of Instrument'".
What does that mean? Turn it ON after you've run the adjustment? Or turn it OFF, preventing further changes? Is it a lock? Or does it just allow the compensation values set during adjustment to be used?
I'm not sure why you'd want to turn it off, but knowing that is probably above my pay grade.:-S
I don't know. On the Trimble unit, you go through and measure the horizontal and vertical errors simultaneously, then the tilt axis.
I presume it uses the horiz./vert. corrections when calculating the tilt axis errors.
I have never had the need to turn off the compensators.
My manual says to run through the collimation routine any time the gun experiences hard handling (shipping), any time there is a 50å¡F temperature change since the last measurement of errors, anytime you change data collectors, and lastly - immediately prior to high precision angle measurement.
I usually only do it twice a year (spring/fall). In the spring I take it out to the airport to measure between some published monuments to check the distance meter.
rfc, post: 333590, member: 8882 wrote: But I discovered another, found in the Special Mode (Menu Mode) screens called "Systematic Error of Instrument Correction".
They say: "Setting ON/OFF for error correction of collimation and horizontal axis for angle measurement. Note: Perform this item after complete section 17.5 'Adjustment of Compensation Systematic Error of Instrument'".What does that mean? Turn it ON after you've run the adjustment? Or turn it OFF, preventing further changes? Is it a lock? Or does it just allow the compensation values set during adjustment to be used?
I would guess you turn it on after you complete 17.5 By my logic, you need to come up with the values you need to compensate out before you can have the machine apply them.
But I don't know. I would probably try to make the machine turn off any buttons bells and whistles, and record several sets of observations then go through the instructions on the same setups, in the order you think you're supposed to, and do the same observations and see if you think it's properly applying the adjustment factors.
Tom Adams, post: 333602, member: 7285 wrote: I would guess you turn it on after you complete 17.5 By my logic, you need to come up with the values you need to compensate out before you can have the machine apply them.
But I don't know. I would probably try to make the machine turn off any buttons bells and whistles, and record several sets of observations then go through the instructions on the same setups, in the order you think you're supposed to, and do the same observations and see if you think it's properly applying the adjustment factors.
Tom, that may be an exercise I can put on my list, but, given my (in)experience, it's not a very sound way to determine if the instrument is set up and calibrated properly. I do know that I don't know enough, to care about whether or not "I think it's properly applying the adjustment factors". I haven't even figured out what they are.o.O I've started another thread asking what each of the parameters are. I know Topcon is not the most widely used equipment here, but i've got to believe someone who reads Beerleg is familiar with the under-the-hood workings of these user adjusted calibrations. If no one surfaces, I might give Hayes a call. I think I've read they're great Topcon people who would have some techies who know.
I was thinking that "completing section 17.5" might clarify things for you. I am envisioning them walking you through checking the direct vertical with the reverse, and getting the split, and figuring out a compensating factor from that. Same with turning horizontal angles. I would at least go through it and see if a lightbulb turns on over your head and you can suddenly see clearer.
Me, I have a topcon IIb. it was their first "total station". It turns angles you read with a vernier, and an internal edm. For an extra it would come with an attachment where you could type in the vertical angle and slope distance and it spits out the horizontal distance. 😉 My dad bought that when he was about the age I am now (and they were brand new)
Reading the bits and pieces of information and suggestions from all the posts led me to confusion. As a result, I completed a fairly comprehensive analysis. Results and comments follow:
Telescope Direct and Reverse Observations:
"Using both faces should eliminate the vertical circle error."(Post No 1) This may not be true in all cases. It is possible that a systematic error could exist at one or more of the vertical circle graduations. If this was the case, then reading one position might provide an accurate reading and the other position an inaccurate reading. Averaging the readings would remove half the error.
The best one can assume is that reading both direct and reverse observation values "probably" will eliminate or minimize the effects of systematic errors. The greater advantage, because of the redundancy, is that error sources or indications are revealed.
Zenith Angles:
For observations made between two points, the only way Zenith Angle pairs sum to a straight angle (post No 11) is if the instrument and target heights are equal for each observation. For example, if observing from point A to B, the instrument height is 5.12 feet, then the target height must be 5.12 feet. Then when observing from B to A, if the instrument height is 4.96, the target height must be 4.96 also.
Elevation Determination as a function of Zenith Angles and Instrument and Target Heights:
Problems or errors with observations could be the result of:[pre]
A. Malfunctioning equipment
1. Loose tripod hinges, clamps or feet
2. Tripod materials expansion or contraction (metal tripods)
3. Instrument damage or adjustment
4. Internal software bugs
5. Instrument sensitivity to radio or electromagnetic signals
B. Improper Instrument Setups
1. hot asphalt
2. mud
3. snow
4. sand
C. Pointing errors
D. Data entry and measurement errors for
1. Instrument
2. Target Heights
E. Operator error[/pre]
Item D is of particular concern. From the data presented, it is suggested that the height from the tribrach base to the axis about which the telescope rotates is the same as that from the tribrach base to the prism center. While it is possible, it has not in my experience been observed. Normally the instrument height above the tribrach is greater than that for the prism center.
In the table which follows note that the elevation differences are not equal for the observation pairs[pre]
100Û?500(32.810) & 500Û?100(32.459) Û? 0.351
100Û?700(41.061) & 700Û?100(40.357) Û? 0.704
and 500Û?700( 8.327) & 700Û?500( 7.817) Û? 0.510.[/pre]
While the Zenith Angle Splits vary considerably, the elevation differences for each pair should be nearly equal. The indication is that instrument and target heights were not accurately measured or recorded. There is very little doubt that this is the single greatest error source.
Zenith Angle Split errors are probably the result of observation problems referenced in items A, B and C. Turning on the vertical compensator, unless the instrument operates in a different manner than the instruments I've used, corrects for systematic errors in single observations. Observing Zenith Angles in telescope direct and reverse positions yields as good or better results. The significant advantage of direct and reverse observations is that sources of error are more readily revealed.
In response to Post No 45 Û?, if as I've stated prior the instrument operates similarly to the ones I've used, then the vertical collimation should be completed with compensation turned OFF. After the collimation procedure has been completed, then compensation can be turned ON. Subsequently, any single, either direct or reverse, Zenith Angle observation is corrected before it is displayed or recorded. Too, if both direct and reversed telescope Zenith Angles are observed, the split should be neglible - near zero.
That is a neat spreadsheet. Do you mind sharing?
Measuring instrument/target heights in dual units helps a bunch with that type of problem.
rfc, post: 333067, member: 8882 wrote: I used tripods with optical plummet prisms at all three points, set the instrument up at correct temperature and pressure, used care centering, measured heights of targets and instrument to .01 feet, etc.
I am wondering what the odds are those HIs and HRs consistantly hitting 4.78' & 4.85'
R.J. Schneider, post: 334020, member: 409 wrote: I am wondering what the odds are those HIs and HRs consistantly hitting 4.78' & 4.85'
I had wondered the same thing.
If it was a scale factor, the elevations should still agree, but be incorrect.
