Traversing

Entering a Foresight

TPC defines a foresight as a point that is measured, then occupied before any other points are measured. A foresight record contains both the measured data used to compute a position for the foresight and the occupied point information like instrument height. Traverse PC uses the Occupied option from the Traverse View Type menu when designating either an occupied or foresight point type.

Note: The Type field will be blank for occupied/foresight points.

Press the down arrow key until a new point is appended to the traverse.
If the point type is blank, the point is considered to be an occupied point. If the point type is other than an occupied point, highlight the point and press [Ctrl]+[F10] or choose Type | Occupied.
Enter the measurement to the foresight. Each time you enter a value, the cursor goes to the next field in the Edit Sequence.
The description and target height are copied automatically from the previous point.

Reading the prompt line

The bottom line of the Traverse View always reminds you where you are. Notice that it displays BS= for the backsight, OP= for the occupied point and FS= for the foresight.

Occupying the Foresight

If you are carrying elevations, enter the instrument height you measured when you moved ahead and occupied this FS.
Press [Enter] until TPC appends another point to the traverse. You are ready to enter the next shot.

Point	Type	Data	Northing	Easting
1			2000	2000
99	BS		1000	1000
2		data	2100	1900
3		data	2200	1920
4		data	2250	1970

Combining Foresight Points and Occupied Points

To reduce the number of records required to traverse, TPC combines foresight data and occupied point data into one record type. Notice that when the point type is blank, the point is an occupied and/or foresight point. A typical traverse looks like:

Point	Type	Data	Northing	Easting
1			2000	2000
99	BS		1000	1000
2		data	2100	1900
3		data	2200	1920
4		data	2250	1970

This traverse starts at point 1 (the first occupied point) using point 99 as a backsight.

A foresight is taken to point 2.
Point 2 is then occupied.
Next, a foresight is taken to point 3, using point 1 as the backsight. Unless otherwise specified, TPC uses the previous occupied point/foresight as the backsight.
Point 3 is then occupied.
Finally, a foresight is taken to point 4, using point 2 as the backsight.

Without combining foresight and occupied points, this same traverse would look like this:

Point	Type	Data	Northing	Easting
1	OP		2000	2000
99	BS		1000	1000
2	FS	data	2100	1900
2	OP		2100	1900
1	BS		2000	2000
3	FS	data	2200	1920
3	OP		2200	1920
2	BS		2100	1900
4	FS	data	2250	1970

Notice that without combining foresights and occupied points, you use three records to record what TPC records in a single foresight record.

For the times when you want to explicitly define the occupied point and backsight as shown here, TPC provides a traverse command. You’ll learn more about the traverse command later.

Changing Backsights

Unless you specify a backsight point, TPC assumes that the previous occupied/foresight point is the backsight

Although this is probably the most common way to traverse, you can still specify a backsight other than the previous occupied point or foresight.

Point	Type	Northing	Easting
3		2000	2000
99	BS	1000	1000

Press [Enter] or the down arrow key to advance to a blank record.
Enter the point label for the backsight and press [Enter]. If the point already exists, press [Enter] again to recall it.
Highlight the point number you want to be a backsight point, choose Type | Backsight (or press [Shift] + [F10]). The point you entered will become the new backsight. TPC will not use the previous Occupied/Foresight point as a backsight.

Using the Traverse Command

The Traverse command adds two points to the traverse - an Occupied/Foresight Point and Backsight Point. Once the points have been added, you can enter coordinates for the added points or recall existing points. The Traverse command saves your key strokes by adding the points and presetting their types.

Point	Type	Data	Northing	Easting
1			2000	2000
99	BS		1000	1000
2	SS	data
3	SS	data
4	SS	data
2			2100	1900
99	BS		1000	1000

Choose Edit | Traverse.

In the example shown here, point 2 was recorded as a side shot along with points 3 and 4.

Then the traverse command was executed, adding the OP and BS records to the traverse.

Point 2 was recalled as the OP and point 99 was recalled as the backsight.

Without the Traverse command, point 2 would have to be shot after points 3 and 4 and its type changed to an Occupied/Foresight so that it could be occupied. Then a BS record would have to be added for point 99.

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