I'm currently supervising the surveying and machine controlled paving operations on a major highways project. We are using SCS/GCS and PCS900 for all of our surveying, grading and paving with the paving op's. All surveys are carried out with SPS930 total stations with MT1000 targets.
When we have carried out as-built surveys we have encountered a number of inconsistant readings in respect of vertical values. This has only come to light as a result of our trialing the MC laying of the binder course to a +/-6mm tolerance.
Trimble advised that we use the MT1000 target in either Passive or Active+ mode so as a precaution I carried out a check on 2 of our MT1000 targets in all 3 available modes. The target was set on a tribrac/carrier on a concrete pillar with a brass pillar plate. The SPS930 was set on another pillar approximately 110m away. The test was carried out in the evening at a time when heat haze was no longer evident, it was slightly overcast and there was no wind. The targets, prisms & diodes show no apparent signs of damage or misalignment.
Measurements were taken (using both SCS900 and Access) to each glass prism in turn and in all 3 modes.
When I looked at the results I found that as expected Passive mode was indeed very consistant with only 1mm variation in the vertical. Again, as expected with Active mode (relying entirely upon the diodes) vertical precision was significantly worse with a range of 4mm (7mm in Access) from highest to lowest. The big surprise however was that the Active+ (diodes to track and passive to measure) results were no better than the Active with an identical 4mm range.
Trimble support, as per usual have very little to offer so I thought I'd see if anyone out there hase encountered similar inconsistancies and has a solution other than the purchase of the new Active Track target at a cost of £1600 each. We have currently had to abandon Active tracking in order to restore confidence in our ability to provide consistant results... So much for Trimbles manopoly of Active Prism technology!
Interesting...
When you say results - are you looking at coordinates or at raw angles and distances?
Given that the Trimble total stations are only good to +/- 3mm plus 3mm per 100m for distance I can easily see a single coordinate being 'off' by more than 4mm.
I think examining the zenith values for each pointing might be more useful
Just my $0.02
Access user here - I believe that active+ (called semi-active in access) doesn't work in tracking mode, you will just get an active measurement. I have a feeling this is what is happening in your test.
On Access you can see when it switches to passive mode. The display will say "changing mode" or similar for a few seconds while it switches tracking mode. Makes the whole thing very time-consuming.
Not to teach my grandmother to suck eggs but do your compensator calibration often and if you are measuring in one face only, also calibrate the vertical angle often. I am not sure where this is in the SCS900 software but it should be there to get the performance out of a 1 second instrument (SPS930).
Hi squowse,
thanks for the response.
ALL measurements are in STD mode (TRK mode used ONLY for general set-out op's)
ALL of our instruments and those employed by our sub-contractors undergo a complete check & adjust every 28 days on a pair of contrete pillars/pillar plates in our main compound.
This issue is present in operations undertaken with up to 12 different instruments/targets used by both the JV and the sub-contractors carrying out the earthworks and paving.
My current thoughts, given that I did not notice any disernable difference in Active and Active plus measurement times in SCS900 is that there may be a bug in the software.
Having compared all three tracking modes in both SCS900 and Access it looks very much like Active+ is nothing of the sort.
Hi Jim,
thanks for the response. In answer my dH values are taken from co-ordinates calculated from single face measurements to each of the 8 prisms in the 3 respective tracking modes.
The SPS930 total station actually specifies that the standard deviations in STD mode are +/-(2mm+2ppm) for distance and 1"(0.3mgon) for H & V angular measure. As such it was chosen because its specified capabilities should easily meet our requirements.
In addition , our 28 day rotation for check & adjust (and recent calibrations) and the results derived leave me in no doubt that the instruments are in good adjustment.
Oh, you missed a zero... ppm being 3mm in 1000000mm (1000m)
Apologies for being pedantic
Just my £0.02
> The targets, prisms & diodes show no apparent signs of damage or misalignment.
Have Trimble check the diodes. I assume your JV bought all of this equipment new. The MT1000 is serialized and should be warrantied.
Hi Roadhand,
Though all of the prisms and diodes appear to be in good order and given that I insist that ALL of the hardware is handled as if it were a newborn, that's next on list if Trimble don't come up trumps in respect of my suspicion that the root cause is a problem with Active+ in SCS900. All my measurements to the same targets with Trimble Access come back as expected.
That said, I'm not going to be holding my breath given the amount of time it took them to take action when we discovered a serious limitation in the way SCS900 works when carrying out a sync of site designs and work orders through TCC. Apparently v3.4 of SCS900 can't handle a sync with TCC if there are more than 900 files, folders etc. stored on the cloud file space. I was very surprised to find that my project was handling so much more data than any of Trimbles other customers, hence their being completely oblivious to the issue. So if you're using SCS900 and TCC on a large project I would suggest you pester Trimble for the v3.4.1 beta which subsequent to my breaking the system now includes a fix.
Back to my targets. Thanks for the suggestion but I guess we'll have to muddle on in Passive mode for now.
I am having TCC Sync issues myself, and like you I tell them and they seem oblivious. I hadn't heard of the file limitations, my problem is cutting work orders and control files out, they never get out of the controller and go right back into TCC the next time they sync. I have talked to 4 different people at four different levels from sitech to Trimble Americas and nobody can give an answer. I work around it with Officesync, its just frustrating to spend all of that money on technology that they sell you on, just to find out it doesn't work.
> My current thoughts, given that I did not notice any disernable difference in Active and Active plus measurement times in SCS900 is that there may be a bug in the software.
>
> Having compared all three tracking modes in both SCS900 and Access it looks very much like Active+ is nothing of the sort.
SCS900 seems buggy, did you get the same results with Access though? Ah I just read below you didn't.
Semi-active, you should see the mode change and the measurement should be the same as passive.
I have one of the new AT360 target on loan from Korec, you can probably borrow one and see if it helps. (see PM)
SCS900 seems a bit of a joke (to me) sometimes. It seems to dumb everything down as if "construction" people are a bit simple. So "semi-active" becomes "Active+" as if we don't know what semi means but we like a big + (and then it turns out it doesn't work but no-one has noticed). I thought Korec's support times were bad until I started dealing with Sitech, although to be fair there are a couple of very good people there when you can get hold of them.
After getting the instruments back from the shop, are you going through the horiz./vert/tilt/active prism collimation routines on-site before using?
You mentioned getting different results with a different controller software, could it be that these collimation values are stored in the DC and each controller has different values or no values?
Have you taken the raw data and calculated the vert. diff yourself by hand rather than using the software?
That 6mm must be a smoothness spec. not a grade tolerance?
Hi imaudigger,
Thanks for the
due to the way in which I conducted the check measurements and the consistency of the inconsistency (Is that an oxymoron? Not sure but I'm sure you get the idea) I don't see any value in reducing the data manually. Should it turn out that the software is for some unknown reason storing eronious angular data rather than simply failing to sight the target correctly I am left with the same problem... A software failure which requires remedy by the manufacturer.
That said I don't currently beleive that this is the case. All evidence thus far indicates at least a failure in respect of the Active+ mode not switching to Passive at the point of measure as it does in Access when using Semi-Active.
Ah TCC now there's a topic.
About 3 months after we started using TCC last year we started to encounter the sync failure. Eventually and I can only assume as a result of my being a massive pain in the arse not to mention the £200,000+ investnment in Trimble equipment by this project, we had an engineer from Trimble on site for a week to look in it.
After much head scratching he established that it was in fact the 900 file/folder limit.
There are really only 2 ways around this problem.
1. Beta v3.4.1 of SCS900
This appears to have removed the limitation.
2. Manually manage the TCC file space by first making regular copies of the "Archive" folder for each controller before removbing it entirely from both TCC and your Trimble Synchroniserdata folder.
Please note that if you are using SCS900 v2.9 the software will NOT automatically remove design data which you have removed from TCC as it does in v3.4. It will ask you what action you want to take in respect of EACH and EVERY conflict (be careful and be certain of the direction of upload/download). Either way you will still have to deal with empty design folders reappearing in SCS Data Manager for any design which you have deleted whenever a controller is sync'd.
As for the control files, this has been a big issue here as we are on to rev31 of our master control file (400+ control points and counting). The failure of the system to remove superseded control files has been reported to both Sitech and Trimble on numerous occasions. I've had the opportunity to speak with a number of Trimble representatives inc. the Region Manager for the UK, Ireland, Africa and Middle East as well as 2 engineers involved with TBC and SCS. As yet no one has been able to offer any explanation for this failure.
+/-6mm is grade tolerence for binder and surface course.
For the most part it's the same staff. All the people I deal with just changed t-shirts when finnings purchased the construction side of KOREC.
Hi guys. I have a question. Today i setup my Trimble S6. I tried the MT1000 setup on a tribrach. I take measurements both passive and active mode but the problem is im 10mm short on the HD compared to the actual measurement using a tape measure. My setup was 2.903 on the TSC3 but twhen i pull the tape is it 2.914. Means that it has 10mm error.
Any idea whats wrong with my setup? MT1000 has a prism constant of +10mm.
Are you taping slope distance or horizontal distance? 😉
Hi all,
I'm only new to Trimble survey products, I've been a Leica user for quite a few years now. I was under the impression that the AT360 target has tightened the vertical accuracy of the readings due to the fact that it's only a single ring of diodes that the jigger locks onto. Correct me if I'm wrong, but the MT1000 has an extra error element to it as the jigger needs to interpolate the point of the prisms because it's tracking an LED signal produced by two different sources at significantly different levels, it is essentially trying to estimate or calculate the halfway point between the upper and lower rings.
My interpretation is that because there is only one ring present on the AT360 target there is no interpolation needed, which should bring the vertical error within 1-2mm, (the diameter of a diode). I would guess there are disadvantages to the AT360 though, a single ring would reduce locking range, and being effectively nothing more than a reflective tape cannister would also mean that its shooting range would be less than traditional glass prisms. In saying this I've tested an AT360's tracking range recently and it followed/read comfortably at 450m, a range that you really don't want to do robotic work unless you're really pressed.
A problem I've found with Access which has really got under my skin this last fortnight is its tendency to change target height when selecting another target. Last week this stung me on a road project. I'd read a back sight using a traverse kit then prepared to take the couple of shots I needed. I entered the height of my pole, then changed from a circular prism to a 360. I didn't notice that when I changed the prism type it changed the height back to the height of my back sight. I only noticed this error when I downloaded the raw data.
I've come across this issue quite a few times, when doing reflectorless work aswell, having it automatically change the height to that of the backsight when changing the prism type again. Really, who came up with this silly idea, and you'd think common sense would prevail, how often does anyone apply a height of target to a reflectorless reading? Any Trimble rep's please take note of this and get it corrected in future updates, the software really shouldn't be changing anything unless the operator is instructing it to.
squowse, post: 428681, member: 7109 wrote: Are you taping slope distance or horizontal distance? 😉
Horizontal distance and even slope distance its the same coz the HI and the MT1000 height is the same.
I have had a lengthy conversation with a trimble tech about the vertical errors I've seen with the mt1000, he confessed the prism is designed for mass production topo level work (as if topo doesn't need to be accurate) not precise vertical measurements. So 5 hundredths of vertical error in 400 feet horizontal distance didn't surprise him. It's been a while since I had this conversation so I don't recall exactly his explanation, but it had to do with all the small prisms on the mt1000 are of poor geometry for the tracking on the instrument to achieve consistent accurate results and that I should be using a larger 62mm prism for accurate tracking. I didn't understand it but when I switched to the larger prism my vertical accuracy consistency improved greatly. Hope this helps.
As for the 10mm tape vs edm distance error I believe 10mm is the mt1000 prism constant so that may be a possibility. Good luck.
