DiNi Leveling Wall Targets – Discrepancy between Robot and DiNi
Just to get going here, I??ll be the first to admit I??m a dummy (and early in my surveying career), but I??m interested in finding out where I went wrong, so I??m all ears.
I thought it would be easy to tighten up my wall target elevations by sighting them with a Trimble DiNi level, but I??m seeing 0.04?? to 0.055?? [vertical] difference between my DiNi ??measurements? and my robotic data, shot with a Trimble S5 and a mini prism. I would be disappointed with 0.02?? of disagreement between the S5 and the DiNi, but a consistent ~0.05?? means something I??m doing is *&@#$ed.
Here??s the robotic situation:
To shoot the wall targets, I used a Seco mini prism taken out of it??s harness thing. This mini prism has a little nipple attached to the back of the prism housing, and I stuck that nipple on the gnats ass of my wall targets which were stuck to huge concrete columns at around 5.20′ from the floor. Having seen weirdnesses on other jobs, I found an EngineerSupply.com video about ??nodal points? and implemented what they discussed in that video by directing the face of the mini prism at the robot (my coworker sighted through the S5??s eyepiece to let me know if I was mis-oriented). I used a 0mm prism offset setting for this configuration.
All robotic shots, including sideshots, were ??repetition shots? (in SurveyPro parlance), i.e. Backsight-Face1, Foresight-Face1, Foresight-Face2, Backsight-Face2.
Backsight/foresight??s were to -30mm traverse prisms, and each leg of the traverse was roughly equal (with a nice long backsight of ~300?? to initiate the traverse).
All sideshots to wall targets were shorter or equal distances than my backsight shots. After station setups, my readouts would report my backsight delta??s, all were less than 0.02?? vertical from the previous setup??s foresight, often they were under 0.01?? from the previous setup??s foresight.
Also, I recently did all three calibration routines recommended for the S5, did them in similar climate conditions?? perhaps one note is that I performed the ??tracker collimation? on a -30mm traverse prism which is much larger than the mini prism I used for my robotic shots on the wall targets (not sure what the significance is there). I do not know the precisions of the traverse/mini prism, but we get them from a reputable dealer in our area (I know the mini prism is a Seco)..
Also, I dutifully monitored the S5??s electronic level bubble throughout each leg of the traverse, so I can verify that the level was less than 10? out of plumb in any direction for any given shot (the level compensator was on the entire time).
Here??s the DiNi Level situation:
As far as I??m concerned this thing lies to me all the time. From its readouts, I can level through an entire site and check in to my original benchmark within 0.002??. Professionally I think that??s great, personally I think that??s bogus, but whatever.
The level has crosshairs visible when looking through the eyepiece. For backsight/foresight shots on my traverse control, I basically point those crosshairs at the barcode of the level-rod, get the barcode into focus, then shoot. After a backsight on a known or computed benchmark elevation, a screen readout reports a Z which is approximately 5.0?? above that known/computed benchmark elevation?? I interpreted this as the HI or height of instrument. I also assumed that if I look through the eyepiece, those crosshairs show me where that Z is, i.e. I can spin that DiNi around and my crosshairs will locate my HI. Have a sneaking feeling that this is where I went wrong.
Anyway, turning a backsighted DiNi to a wall target, I see those crosshairs overlaid on my coworkers tape measure, which has 1.00?? pinned at the gnats ass of my wall target, and is dangling vertically. I note the Z of my backsighted DiNi readout, and then I count how many hundredths, plus or minus, my wall target is from the crosshairs with that Z.
Back at the Office:
Back at the office, I start adjusting my robotic data with my level data, none of my traverse elevations change by more than 0.015??, and my vertical misclosure for my entire traverse is around 0.015??.The important part is that I improvised because I couldn??t use the level-rod to shoot the wall targets – I just followed the procedure above and wrote all the HI+/-tapemeasure elevations in my notebook.
I would love to hear any feedback, thanks.
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