Outline Setting up Sokkia SET 4BII Total Stations
- Set up and level tripod over point.
- Attach and setup
SDR33 data recorder if you are using one .
- Turn Instrument ON.
- Loosen the clamp on the telescope.
- Rotate the telescope about the vertical axis by 360°. You should hear a beep at this
- Rotate the telescope about the horizontal axis by 360°. You should hear a beep at this
- Configure the total station
- Determine the orientation to a backsight point.
Point the total station at this point, and take your backsight. This can be done manually
using the instrument keyboard or via a SDR33. If the current station and backsight station
are in the SDR33 memory, then it will determine the angle and set the instrument,
otherwise you will have to provide coordinates and angles (details given below).
You are now ready to start using the Instrument
This can be one of the most time consuming procedures in surveying, and one of the most
crucial. Any error in setting up the tripod is carried through the entire survey.
Generally small setup errors (1 or 2 mm) are not a problem because they are
non-systematic, and the EDM on Total Stations have an error or ±3-5 mm. I suggest the
- Setup tripod. Open up the tripod and extend the legs. Adjust the approximate
height so that the total station will be at eye level. Set one leg on the ground. This
will be the "anchor" leg, and should not be adjusted in the following procedure.
Holding the other two tripod legs, and keeping the anchor leg in the same position, move
the tripod until the plum bob (or optical plumit) is over the point. Do not worry about
having the tripod level. When you are over the point, anchor the two remaining legs. You
should still be exactly over your point. I suggest that you attach a tribrac to the
tripod, and use one of the reflector posts - these contain an optical plumit. Another
option is to attach the Total Station at this point. Just be careful!
- Level the tripod. By changing the length of two legs you used to position the
tripod, level the top surface of the tripod using the bulls-eye level. The bubble should
be within the inner circle. Be as precise as possible. Do not change the length of the
anchor leg. After this procedure you should still be directly over the same point you
were over in step 1.
- Attach instrument to tribrac. Set instrument into tribrac and lock in place.
Align the long bubble-level between two posts of the tribrac. Turning BOTH posts in
opposite directions, center the bubble in the level. Turn the Instrument though 90° to
align it with the third leg. Turn only the third leg until level. The instrument will now
- Check alignment over point. Use the optical plumb on the instrument to check that
you are still over your point. If you are not, you may slide the entire tribrac assembly
slightly to get over the point. If you move the tribrac, repeat the leveling procedure.
- Set up a notebook page, or use the Instrument Station Setup Checklist. You
will fill out this page before you enter all the numbers into the Total Station. This is
done to make sure that nothing is missed.
- Measure Instrument Height. Record instrument height. This should be
measured from the ground to the tilting axis of the instrument. If setting up over a
benchmark, measure height to top of BM and the height above the ground. The titling
axis of the instrument is marked on the side opposite from the on/off switch. It is a
small hole inside a raised circle.
- Measure Temperature, and record,
- Measure Pressure, and record.
- Enter PPM Correction into Total Station. The speed of light in air changes
with the density of the air, so we must make a correction to the measured distance. This
is done by measuring the temperature and pressure. The correction factor is in terms of
parts per million (ppm), or mm/km. From the temperature and pressure you can look up the
correction factor in a chart included with the total station, or you can enter the
temperature and pressure in the instrument and it will calculate the correction
We apply the correction to the instrument. This way the corrected distance is passed to
the SDR33 notebook. You must make sure that the SDR does not repeat the correction!
To enter the temperature and pressure, press the key (bottom right) then the EDM key (top
left). From the menu select item [3. ppm], then item [2. Temp & Press]. Enter the
temperature and press ENT, then enter the pressure and press ENT. At this time the top
item in three line display above the main display will show the ppm correction.
- Record instrument coordinates. Eo, No, Ho are the E
and N coordinates or the station. Ho is, for our "plane-table"
mapping purposes, the ground elevation. For the first instrument station you may want Eo =
0.0, No = 0.0, and Ho = 100.0. For subsequent instrument stations use the coordinates of
the point that you are setting up on. These will be entered into the SDR33 notebook if you
are using one.
- Record reflector heights and prism constants for each reflector. The instruments
are set for a default prism constant of -40mm. Some of the prisms we have are -30mm
prisms. Measure the reflector height, DO NOT rely on the calibration on the rod's being
- Enter a backsight, or desired angle. Details given below. How you enter this
depends on if your are using a SDR33 and on how much information the SDR33 contains.
You should have the SDR33 notebook setup correctly before you enter a backsight to
orient the Total Station. The backsight is a key step in setting up the instrument
correctly. It is essential to get the instrument oriented correctly, and it is impossible
to orient the instrument with any accuracy using a compass. Surveying measures the angle
between two lines of sight, the actual bearing of the lines is generally not of
importance. The important thing is to get a survey internally correct. You can establish
the absolute orientation of your network of points by surveying in two known locations.
For example, you may use existing benchmarks, or GPS to control two of your points.
Using the SDR33 Electronic Notebook
The SDR33 will not let you begin to collect data without either specifying a backsight
or telling it that no backsight is needed.
Case I. Starting a new job
If you are starting a new job this is the time to set up your coordinate system. If you
are making a control-point map then you will want to orient "North" along the
long axis of your mapping project. Point the total station along the long axis and use the
instrument control panel to set the direction to zero (see instructions below). Then, when
the SDR33 prompts you for the instrument station number, enter any number (usually 1).
When prompted for a backsight reading, just press OK, and then confirm that you want to
skip the backsight. The SDR will not reset the instrument under these conditions.
If you are making a precise survey of a quadrilateral, then it is the angle between
lines that is important, so you do not need to set a backsight. In fact, you do not need
to set the orientation of the instrument, you can just start taking readings. When the
SDR33 asks you for a backsight, just press OK and confirm that you do not want a backsight
Case II. Continuing an existing job
If you are continuing a job where it is important to orient the instrument, you should
set up the instrument over a known point, and set up a reflector over a second known
point. When starting to use the SDR33 specify the station number where the instrument is
located. If the point number exists in the current job, then the SDR will display the
stations coordinates and ask you for a instrument height. If the point number is not found
in the current job then you will need to enter the coordinates of the current instrument
station and the instrument height.
After specifying the location of the instrument you have to indicate the backsight
point number. Again, if this point exists in the current job, you will asked to point the
instrument at a target over this point and take a reading. If the point does not exist,
you are given the choice of either entering the coordinates of the backsight point, or the
direction to that point. Once you have entered the information about this point, then you
will be asked to take a reading to this point
The SDR will set the horizontal circle to value you entered, or from it's record of
point. It will then take a reading to the point and verify that the range and elevation
difference match what is has in the job database (if it is a pre-existing point).
Using the Total Station Keyboard
Press the  key. This will put the display in theodolite mode. The vertical (ZA) and
horizontal (HAR) angles will now be displayed.
Point the Total Station at your target, or some clearly defined feature that you can
accurately line up on again, and either press:
then the [0 SET] key to set a the instrument to zero (North)
then the  key. Now type in the horizontal angle in the form of ddd.mmss,
where d is degrees, m is minutes, and s is seconds using the numeric
keypad. Press when done.
Questions? Comments? Contact: CruikshankK@pdx.edu
Page Last Updated:
May 13, 2005