Total Station

How to Check a Total Station

How to check a Total Station.

A Total Station should be checked at least once a month or before any precise work is to be carried out.

The checks on a Total Station should comprise of a five-point check carried out in the following order.  This is pretty much the same method employed when checking a theodolite.

1.     Plate Bubble Check.

1.1.    Set up the instrument on a sturdy tripod.

1.2.    Turn Total Station until the bubble tube is parallel with 2 of the footscrews, and level the bubble carefully.

1.3.    Turn the Total Station through 90 degrees, and level the bubble using third footscrew carefully.

1.4.    Turn the Total Station back through 90 degrees, and re-level bubble if necessary. Keep repeating this process until you are confident the bubble rests in the centre.

1.5.    Then turn the Total Station through 180 degrees. The bubble should be central if correctly adjusted.

1.6.    If the bubble does not stay central, then you are best advised to have it adjusted, or repaired, and calibrated by your specialist survey equipment supplier.

 

2.     Optical Plummet Check. (There are two types of optical plummets.)

2.1.    Fixed in Tribrach.

2.1.1. Having set up the Total Station and checked the Plate Bubble as described above, level the tribrach with Total Station or plate level over a point defined by a cross (the finer the cross the better).

2.1.2. With a sharp pencil trace the outline of the tribrach base plate on the tripod head.

2.1.3. Release the retaining screw slightly and carefully turn the tribrach through 120 degrees keeping within the marks on the tripod.  Re-level and sight the cross and note if the cross is not in the centre.

2.1.4. Repeat, turning through a further 120 degrees. The cross should be central each time.

2.1.5. If the cross is not in the centre each time then you are best advised to have it adjusted, or repaired, and calibrated by your specialist survey equipment supplier.

2.2.    Revolving Plummet. (Fixed in the Total Station or plate level.)

2.2.1. Having set up the Total Station and checked the Plate Bubble as described previously, level the tribrach with Total Station or plate level over a point defined by a cross (the finer the cross the better).

2.2.2. Level and centre over a point defined by a cross.

2.2.3. Rotate the Total Station through 120 degrees and observe the cross.  The cross should remain central.

2.2.4. Rotate the Total Station through a further 120 degrees and observe the cross.  The cross should remain central once more.

2.2.5. If the cross is not in the centre each time then you are best advised to have it adjusted, or repaired, and calibrated by your specialist survey equipment supplier.

 

3.     Horizontal Circle.

3.1.    Set up and level the instrument.

3.2.    Select and sight a well-defined distant point, this should be at least 100m away and you should also be careful to ensure a clear line of sight (A cool overcast day would be ideal).  Read the Horizontal angle scale (H1) and note down your reading.

3.3.    Transit the telescope and re-sight the same point on the opposite face.  Read the Horizontal angle scale (H2) and note down your reading.

3.4.    Work out the difference between H1 and H2.  The difference between H1 and H2 should be 180 degrees.  However, your angular error should be less than the stated accuracy of the Total Station.

3.4.1. For example, H1 = 180 degrees 0 minutes 0 seconds.  H2 = 0 degrees 0 minutes 3 seconds.  Then (H1)-(H2) =179 degrees 59 minutes 57 seconds.  This is a 3 second inaccuracy.  If the Total Station is classed at 5 second accuracy, then the result would be acceptable.

3.4.2. If the result is greater than the accuracy stated on the Total Station then you are best advised to have it adjusted, or repaired, and calibrated by your specialist survey equipment supplier.

 

4.     Vertical Circle.

4.1.    Set up and level the Total Station as before.

4.2.    Select and sight a well-defined elevated point.  Again this is best done on a cool and overcast day.

4.3.    Read the vertical angle scale (V1) and note down the reading.

4.4.    Transit the telescope and re-sight the same point on the opposite face.

4.5.    Read the vertical scale (V2) and note down your reading.

4.6.    V1 and V2 the abstract angles of elevation or depression should total 360 degrees.

4.6.1.  For example, V1 = 100 degrees 0 minutes 0 seconds.  V2 = 260 degrees 59 minutes 57 seconds.  Then (V1)+(V2) =359 degrees 59 minutes 57 seconds.  This is a 3 second inaccuracy.  If the Total Station is classed at 5 second accuracy, then the result would be acceptable.

4.6.2.  If the result is greater than the accuracy stated on the Total Station then you are best advised to have it adjusted, or repaired, and calibrated by your specialist survey equipment supplier.

 

5.     Trunnion Axis.

5.1.    Set up and level the instrument as before.

5.2.    Sight a well-defined high level point with the centre of the cross hairs (like a steeple or a fixed radio mast.

5.3.    Depress the telescope and read a tape set (perpendicular on the floor) close to the instrument (T1) and record your reading.

5.4.    Repeat on the opposite face and read the tape again (T2).

5.5.    The readings T1 and T2 should be equal.

5.6.    If the result is greater than the accuracy stated on the Total Station then you are best advised to have it adjusted, or repaired, and calibrated by your specialist survey equipment supplier

5.     EDM Check

5.1.    Set up a well defined distance between two know points, ideally over 30m. Two hilti nails would suffice, ideally at the same level.

5.2.    Measure the distance accurately with a steel tape.

5.3.    Set up and level the instrument as before over one of the hilti nails.

5.4.    Using a prism on the far hilti nail, measure and record the distance.

5.5.    Compare the readings from the steel tape and the distance measured by the total station.  This is a gross error check for distance measurements and errors of the order of 2 or 3mm will usually be acceptable.

5.6.    If the result is greater than the accuracy stated on the Total Station then you are best advised to have it adjusted, or repaired, and calibrated by your specialist survey equipment supplier

 

In addition to these manual checks, often the Total Station will have a check and adjust programme.  This programme will usually require a prism station to be set up at a set distance away from the Total Station for it work.  This will alter the target recognition values within the Total Station, and provide accurate readings to the prisms used.  The more time and care you take with the above checks, the better the accuracy you will be able to achieve with the Total Station you are using.

Leica TS16 Side


Top Tip for Getting the Best Results When Checking Total Stations.

Whenever you are checking an Automatic (Dumpy) Level, or a Rotating Laser Level, or a Total Station, make sure that the tripod head is as close to being level as possible. Whenever I am carrying out these checks I like to use a bullseye spirit level like this one I bought from Amazon. Its 65mm diameter so it spans the tripod access hole and is large enough to be easy to set.

Large Bullseye Spirit Level
65mm Large Bullseye Spirit Level.