# Using Data Sets

Data sets are multiple observations that are meaned to get an average result. TPC allows you to enter sets for both side shots and foresights in the Traverse View. You can take as many sets as you like - the more sets, the better the mean.

## Choosing Set Options

• Tools | Program Settings | Angle sets to display the Angle Sets dialog.
• Choose the set type you want to use. The set options in the list are explained later in this chapter.
• Choose [X] Keep F1 if you want to keep the face one measurement instead of the mean. If you turn this option on, TPC will still check the set to make sure it is within tolerance.
• Choose the number of sets you want to turn. It is easy to add additional sets in the Traverse View, so if you are unsure, leave this at 1.
• Enter your allowed tolerances. If the computed mean is outside of these tolerances, TPC will display an error message when it computes the mean.

## Entering a Set

• Highlight the foresight or side shot you want to enter the set for in the Traverse View.
• Choose Edit | Insert Set. TPC will insert the set records based on the type of set you selected and the number of sets you entered.
 Point Type Data 1 2 BS 3 FS

The example shown here is a direction method (BFFB) set, where B1 and B2 are the normal and inverted backsight reading and F1 and F2 are the normal and inverted foresight readings.

B1=Normal backsight. (face 1)
B2=Inverted backsight (face 2)
F1=Normal foresight (face 1)
F2=Inverted foresight (face 2)

 Point Type Data 1 2 BS 2 B1 3 F1 3 F2 2 B2 3 FSM

Notice that the letter ‘M' is added to the mean FS type for point 3, indicating that the data is the “Mean” of a set.

 Point Type Data 1 2 BS 3 F1 3 F2 2 B2 3 FSM

## Combining the BS and B1 records

If a BS point type follows the occupied point and the BS point has horizontal circle data, the B1 record is not added. Additional sets to the same foresight or side shot will include the B1 record since the additional sets cannot share the BS point type.

## Entering another set

• Highlight the FSM or SSM point.
• Choose Edit | Insert Set.

You can include as many sets as you like this way. Each additional set will repeat the set type selected in the program settings.

TPC combines each set to compute the mean. The means of each set are not displayed.

## Field angle verses horizontal circle

Since BS, B1, B2, F1, F2 and F4 point types store measured data, they all display the horizontal circle, not the horizontal angle. In the Traverse View, the column heading is HA since the column contains both angles and circle readings.

Mean records (FSM and SSM) contain the computed mean horizontal angle, not the horizontal circle. This angle is turned from the BS point and is not dependent on the horizontal circle reading of the BS or B1 record. It is dependent only on the position or reference azimuth of the backsight.

## Measuring the foresight

In any set, you must measure the normal foresight, but you may choose to record the inverted foresight instead of measuring it. TPC means the foresight distances if both the normal and inverted distances are measured.

 Point Type Data 1 2 BS 3 FSM

## Repetition Set Types

Repetition sets use the lower motion tangent screw or the hold button on the total station to turn the total station without changing the horizontal circle reading. The sequence of shots in a repetition set is important and always involves sighting the backsight with the lower motion and sighting the foresight with the upper motion.

TPC allows two different repetition sets. Using the letters B for backsight and F for foresight, they are BF2 and BF4.

BF2

This is a STANDARD "Repeat Angle" set in which the inverted backsight is not recorded. Since the gun is inverted and turned to the backsight using the lower motion, the horizontal circle reading does not change from the first foresight to the second backsight. With this assumption, the second backsight is not recorded. Your total station must have a lower motion tangent screw or a hold button to use this method. The sequence is:

• Enter the backsight circle reading for the BS or B1 record, (you do not need to zero the gun on the backsight but most people do). Release the upper motion on your instrument and turn to the foresight F1.
• Enter the foresight data for the F1 record, lock the upper motion, release the lower motion, invert or plunge the scope, and turn again to your backsight.
• Rotate the scope to your foresight with the scope in the inverted position.
• Record your data, (F2). TPC will compute a mean for the horizontal angle based on the recorded horizontal circle readings. If you have also recorded an inverted vertical circle reading, it will mean those. Recorded distances will also be mean. Recording a vertical circle reading and a second distance is optional.
 Point Type Data 1 2 BS 3 F1 3 F2 3 FSM

In the example shown here, the BS record contains the B1 data, so B2 is not needed. Most of us who have been surveying for more than 20 years will remember this a doubling angles and we did this because it was easy to figure a mean without a calculator.

## BF4

This is a STANDARD "Repeat Angle" set in which the inverted backsight is not recorded and the foresight angle is repeated four times before being recorded. This is referred to as “cranking the angles four times”. The sequence is:

 Point Type Data 1 2 BS 3 F1 3 F4 3 FSM

• Record the horizontal circle reading for the BS or B1 record, (you do not need to zero the gun on the backsight but most people do). Release the upper motion and turn the scope to the foresight, F1.
• Record the data for your shot to the foresight F1. Lock the upper motion and release the lower motion and invert the scope and re-sight the backsight. Repeat this process until you have completed four cycles. Notice that each time you re-sight the backsight the scope is plunged.
• In this sequence, the final shot to the foresight will be with the scope in the inverted position. Record your data after sighting the foresight for the fourth time (F4).

TPC will compute a mean for the horizontal angle based on the recorded horizontal circle readings. If you have also recorded an inverted vertical circle reading, it will mean those. Recorded distances will also be mean. Recording a vertical circle reading and a second distance is optional

## Direction Set Types

Direction sets use only the upper motion tangent screw. A direction set consists of a normal and inverted reading to the backsight and a normal and inverted reading to the foresight. The order of the readings is not important.

TPC allows two different repetition sets. Using the letters B for backsight and F for foresight, they are BFFB and BBFF.

## BFFB

This is the classic “Direction” method. It is the preferred method for total stations without lower motion tangent. The sequence is:

• Enter the backsight data with the scope sighting the backsight point (you do not need to zero the gun on the backsight but most people do).
• In the normal scope position, release the upper motion and turn the scope to the foresight point, enter your field data for the shot to the foresight point [F1].
• Plunge the scope to the inverted position and re-sight the foresight. Record the data to F2.
 Point Type Data 1 2 B1 or BS 3 F1 3 F2 1 B2 3 FSM

Using this method, the final backsight reading should be close to 180°. The amount that the final backsight differs from 180° is the error of the set.

 Point Type Data 1 2 B1 or BS 2 B2 3 F2 3 F1 3 FSM

BBFF

This is a variation of the “Direction Method” used in underground mining and other operations where it is a real time saver to take both the normal and inverted backsights, then move to the foresight and take the normal and inverted foresights. The sequence is:

• Enter the backsight data with the scope sighting the backsight point [B1] (you do not need to zero the gun on the backsight but most people do).
• Plunge the scope to the inverted position and re-sight the backsight. Record the data to [B2].
• In the inverted scope position, release the upper motion and turn the scope to the foresight point, then enter your field data for the shot to the foresight point [F2].
• Plunge the scope to the normal position and re-sight the foresight. Record the data to [F1].

Remember, once the gun is set to the first backsight, only the upper motion is used to release and lock the horizontal circle.

## Multiple Sets to the Same Foresight

If you include more than one angle set to a foresight, the sets are meaned to create the FSM or SSM record. You can include as many sets as you like to a foresight or side shot.

Error: Set Tolerance
FS=3 Set #1
+-Hc=0°04'30”
Error:Set Tolerance
FS=5 Set #2
+-Hc=0°02'15”
Error:Set Tolerance
FS=6 Set #1
+-Hc=0°02'00”
3 Errors

## Checking Set Tolerances

Set tolerances are checked as you enter the set data. If the set is not within tolerance, the computer beeps and the set error is reported in a popup box. The mean will still be computed and displayed with the set.

If the set is out of tolerance, you can repeat the set measurements using the existing set records. A new mean will be computed and the tolerances checked again.

To check the tolerance of all the sets:

• Choose Tools | Recompute

Sets that are not within tolerance will be displayed in the preview error log.