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

Entering a Set

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

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:

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

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:

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:

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:

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

Related Topics

Traverse View
Entering Traverse Data
Entering Side Shots
Displaying Raw Data
Recomputing a Traverse

Editions

Premium, Professional