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Trimble SPS930 Leveling Issues

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Last Post by jitterboogie 6 years ago

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DSIntern

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In need of some help

?ÿ

I am very new to surveying (Been interning at a heavy civil construction company for 4 months now) and am having issues with the Trimble total station (Company purchased it 10 months ago). As the weather has gotten colder (-15 to 0 celsius), the total station drifts out of level very quickly and at a consistent rate. I assumed it was station/tripod expansion or just needed a compensator calibration and have been making sure to give at least two minutes of cool down time per degree difference outside, and a calibration every time with no luck so far. I have also tried ensuring fresh batteries, multiple tripod locations, multiple new tripods (tri-max), and finally disabled the level compensator and setup but still noted substantial drift.

?ÿ

Has anyone dealt with issues like this or have any advice? I want to cross off all potential issues before having it serviced.

Posted : January 6, 2021 7:23 pm

brad-ott

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Is this possibly a freeze/thaw ground conditions issue? ?ÿI have had similar trouble in the past with cold weather setups. ?ÿAfter a time the sun melts the ground ever so slightly around one or two of the tripod feet. ?ÿThere have been many excellent discussions here with very good tips. ?ÿI hope some search efforts will help.

Posted : January 7, 2021 9:01 am

va-ls-2867

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Ground thaw is my first guess.

?ÿ

Posted : January 9, 2021 5:09 pm

fairbanksls

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I avoid storing and transporting tripods in a heated area.?ÿ Immediately after setting up I'll kick snow around the legs if it's available.

Posted : January 9, 2021 7:05 pm

kenl

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Pile snow around each leg before you finish leveling or put each leg on a flat rock or small board

Posted : January 11, 2021 1:07 am

DSIntern

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Thanks for the help everyone.

Made sure to cover each leg with as much snow as I could reasonably find the last two days, and so far has helped. One day was quite cold with a lot of sun and struggled with some drift (not as bad as its been), second day was overcast and cold but faired much better (releveled every 2 hours). I'm going to assume I'm dealing with some ground thaw and uneven expansion due to sun.?ÿ

Posted : January 11, 2021 1:55 pm

brad-ott

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https://surveyorconnect.com/community/surveying-geomatics/freeze-thaw-tripod-sinking/

Posted : January 12, 2021 8:23 am

jitterboogie

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Weight of the total station and tripod are creating downward pressure, and melting the points below the pins/feet on the ends. Kinda like skate blades, kinda....

?ÿ

Get some 2x2 oak hubs( i was told these are called guineas, go figure) softer wood might not work, and pound those in first about 6-8 inches. If youre in permafrost, good luck.?ÿ Usually the top layer of soil is either mostly organics( forest floor etc) or topsoil, and below that first layer usually wont be rock solid ice, just depends on snow cover, and length of subzero.

Additionally, if youre on top of ice/snowpack, larger still hubs/guineas and maybe even a few pieces of marine grade plywood under each foot/pin to lessen the point force of the sharpen end of the points will help.?ÿ It just depends.?ÿ?ÿ Good Luck!

Posted : January 12, 2021 8:38 am

jitterboogie

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