I just got off the phone with our equipment dealer. We have a Sokkia CX103 in for a calibration because of noticeable vertical errors.
I performed a field calibration on this instrument a few months ago when it went haywire. It was about 60° out and I ended up getting about 2 minutes of vertical arc error. The gun seemed to be working correctly and regular checks proved so.
We haven't calibrated lately and the error showed back up. I'm sure the cold had much to do with it. Still, it never sat well with me that the gun was compensating for over 2 minutes of vertical error.
I was told today, at 68°F, said gun has 20" vertical error. I was told this is normal and many other total stations are that way or worse.
What is your knowledge/experience in this matter?
I've run the collimation routine on several Trimble robots over the years and I always get results around 0" to 10" both vertically and horizontally.
I was also told this gun has about 1/2" arc error change for every degree of temperature change. For this, we should calibrate at least every 30°F in temp change. I agree that we need to run the calibration routine more often.
Also, the compensator itself takes about 20 seconds to settle down at cold temps of around 0°F. Wow, that seems like an awful long time. I was told if we did not wait for it to settle down, we easily could be taking shots with 2 minutes of vertical error in them.
So, are all total stations this sensitive?
Good thing we keep our equipment in the trucks. Spec shows an acclimation time of 1 minute for every degree in temperature change for the instrument before accurate work can proceed.
I worked with several manual Sokkia instruments at my previous employment and the guns were calibrated regularly. No matter the temperature, the guns were typically running about 20" off on vertical. I actually mispoke when I said no matter the temperature. Below 15 degrees, neither the gun nor the crew worked well or accurately, but those days were very few and far between.
As a side note, I got a job once in North Carolina in the winter because all crews were on a large wooded topo and accidentally set the woods on fire. While the future topo went easier, one employee mouthed back to the boss after a well deserved ass chewing and I got his job.
I've noticed that right around -25 F, the total station and data collector get kind of cranky and the electronics and LCD displays begin to get really, really slow. Vertical collimation and angle closing doesn't appear to suffer much though, go figure. I just try and avoid rapid changes in temperature.
> As a side note, I got a job once in North Carolina in the winter because all crews were on a large wooded topo and accidentally set the woods on fire. While the future topo went easier, one employee mouthed back to the boss after a well deserved ass chewing and I got his job.
Part of that I can laugh with because - been there done that. I didn't get the ass chewing thank goodness. Me and a partner were high up on a mountain with freezing rain blowing sidewise. I called that job off for the day being as I couldn't see through the gun.
A few years later at another company it was about 10 below zero. Near Mtn. Aire in Yancey county. The gun would only stay on for a few seconds and the data collector just wouldn't come on at all. Then we got stuck and the bulldozer trying to pull us out broke loose and starting sliding down the road. Needless to say that day got cut short as well.
> As a side note, I got a job once in North Carolina in the winter because all crews were on a large wooded topo and accidentally set the woods on fire.
Har! Long ago I was on a 5-man BLM Cadastral Survey crew in the goforsaken woods of North Idaho; part of my job was to have a small fire going at the next instrument setup when the I-man got there, to warm his hands. Got real good at starting a fire in a minute or two that would last five minutes or so.
BTW, no problem with the cold and the instrument, no batteries involved.
