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By Mick
Capman,
PSFM President (Kalamazoo County Sheriff – Retired)
Ever step up to the
tripod and said to your self,
“oh boy … how do I level
this thing again?”
The answer might well
depending on who you ask and what their
profession is, as some might say there is only ONE
way to correctly level the total station.
We offer here one simple
solution on how many of us are accomplishing this necessary
and all-important task in relative ease.
We must first appreciate the
fact that “accuracy rules!” and that there is
no compromise to precise locations of forensic
evidence discovered at the scene.
Most recommended electronic
total stations are equipped with either a single or
double-axis compensator and will not
operate (take distance measurements) unless the
Instrument is level to within the manufacturers
specifications.
Users are
encouraged to refer to Instrument manufacturer manuals for
these specific configurations.
Most total stations are also
equipped with two external leveling bubbles. One
just atop the screen (Sokkia- horizontal,
spirit level; Leica- circular bulls eye bubble), and
one on the tribrach (bulls eye bubble).
But back to our recommended
“simple solution” for this task!
After choosing the R.P./Instruments
location, spread the three-tripod legs sufficiently (some
recommend a 60-deg.spread) to provide for a good, stable
Instrument platform. Place the Instrument on the tripod’s
“faceplate” and tighten the beneath hand-screw
sufficiently firm to prevent any incidental Instrument
free-rotation.
Clue:
Position the tribrachs’ bulls eye bubble closest to
you. If using a “rotating tripod bracket” as seen
here, position this first on the ‘faceplate’ then mount the
Instrument on top.
You have undoubtedly noticed
on the Instruments lower portion, called the
Tribrach (seen here), three (3) knobs. These
knobs when used independently or together affect a change to
the “tilt” or “pitch” of the Instruments
structure itself.
You should note as well that
each knob shaft has a neutral or “common” setting somehow
scribed or otherwise noted on the shaft. This is
essentially the “midpoint” for knowing the half-way motion
UP or DOWN.
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Step 1-
Set all three knobs to the midpoint, neutral or “common”
setting position.
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Step 2-
Stand squarely between any two sets of tripod legs
with Instrument screen facing you.
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Step 3-
Using your RIGHT HAND, turn it
palm down and place on the tripod leg at point where it
telescopes ~ see next picture. Use LEFT HAND to unlock
tripod leg motion and, while watching the bubble on the
tribrach, slide/telescope up or down the tripod leg.
When
bubble is at either the (imaginary) 12 o’clock or
6 o’clock position (see below diagram), lock down
the tripod leg motion.
-
Step 4-
Move either to your Left or
to your Right, between another two sets of tripod
legs, and repeat Step 3 above. When finished,
stay positioned here for a moment.
-
Step
5-
Now,
simply rotate the leveling knob directly in front of you
in one direction or the other, to effect the ‘tilt’ of
the bubble, placing it exactly in the center position.
If however the
bubble appears to slide left or right towards the outside
the center ring, use the two ‘distant’ leveling knobs
in concert with one another, rotating them together in
opposite directions, to effect a ‘pitch’ of the
Instrument forcing the bubble towards the center leveling
ring.
If your instrument is
equipped with a laser plummet (shown above) and once
the Instrument is leveled, the precise R.P. location
should be marked or otherwise noted.
Once you have leveled the
Instrument, it is then time to Zero-SET the
Instrument towards a northerly, compass direction, a topic
covered elsewhere.
It is fair to note that
so long as the Instrument is leveled within a reasonable
time ~ that it is leveled to the extent that it permits
distance measurements, no matter the procedure to get it
level, you should be ready to commence your scene
diagramming efforts. |
