Home > Survey Mode > Reductions > Levelling > Reduce Field Book

Reduce Field Book

Process Levelling data from the spreadsheet.

This function allows you to reduce and adjust spirit levels by the rise-and-fall method.

Two basic types of fieldbooks are catered for:

• The first is for the reduction of a normal level traverse.

• The second is an adaptation for the levelling of road cross-sections. The cross-section level data is recognised as such by the presence of a "#" (indicator for chainage) in the first column.

See the New Field Book section for details.

Before running a reduction make sure that the Output window is visible.

The field book data are reduced and the mis-closure is calculated and displayed in the Output window for adoption. If the mis-closure is accepted, the adjusted elevations are calculated and printed.

In the case of a loop (traverse starts and ends on the same point), there is the option to also adjust the traverse onto the elevation of a known turning point. Any common points (points with the same name) will have their elevations meaned. If there is no particular turning point, or there is a turning point but its elevation is unknown, the default turning point elevation should be accepted. In this case there is no re-adjustment of the traverse but the common points are still meaned.

An option exists to write the elevations as the z ordinates of the points bearing same name in the database.

If the mis-closure is unsatisfactory and the level traverse is either a straight run or a loop without common points, there is very little that can be done except to inspect your field book entries very carefully. However, if there is a loop that contains common points in the forward and back runs, any mistake can be rapidly isolated by running the full reduction and looking for anomalies in the final means.

If the Level Traverse is of a road, it is advisable to create the chainages in Horizontal Alignment in the Road Menu and store them before reducing the field book so that the final elevations can be automatically added to the road chainage coordinates on file.

In the case of levelled sections, the option is provided to store the cross-sections in Civil Designer ASCII format so that they may be imported into a road database at a later stage.

Procedure

1. The fieldbook misclosures are first calculated and displayed.

2. Confirm if you want to proceed with the adjustment.

Click Yes to proceed with the adjustment; or No to cancel the adjustment.

Cancel the Adjustment

If you click No:

1.  You are asked if you want to carry out an error trace on the field book. Click Yes to have the error trace printed.

2. The error trace consists of a list of the change points in the levelling loop and their calculated elevations. The Bend Point Details display.

3. If any stations have been occupied twice in the run, both calculated elevations and the difference between them are listed.

Proceed with the Adjustment

If you click Yes:

1. You are asked if you want to update the elevations of the points in the terrain database.

2. Click Yes to have points in the database, with the same name as points in the field book, updated with the calculated levels.

3. If the level fieldbook represents a closed loop, i.e. the start and end point have the same name, you have the option of readjusting the levels onto the loop turning point. In other words, a mean correction for each half of the loop is calculated and added to the calculated levels.

4. Click Yes to have the readjustment carried out.

5. The Bend Point Details display. Confirm the name and elevation of the loop readjustment point and click OK.