Surface traverse
With this function you can calculate and store new stations in the database. The backsight and setup stations, which must already be stored in the database, are entered and their coordinates are displayed for verification. The observation data which includes horizontal angles, vertical angles, slope distance and instrument and target heights are entered. The coordinates for the new station are then calculated, displayed and stored in the database.
To run this function: Choose Survey > Surface surveys > Surface traverse, or...
level_area for new stations
All stations in a survey database are grouped by the level_area field so that it easy to reference stations in the same level/area of the mine. You must enter the level/area into which the new station/s being created by this function will be assigned.
Details for Traverse report
Enter the names of the persons who will enter and check the calculations. Also enter the field book which contains the original field observations and the page reference in that field book. This information is recorded in the database for each new station that is created by this function.
Define the Traverse Report File
Enter the name of the report file to be created in the Location field. Choose the report type using the Output report file format field.
Complete the Traverse Report Details form and choose Apply to display the Surface Station Traversing form.
Backsight
Enter the name of the station which will be used as the backsight station for this section of the traverse. After entering the station name and pressing return, the coordinates of the station will be obtained from the database and displayed for reference.
Setup Station and Axis Height
Enter the name of the station which will be used as the setup station for this section of the traverse. After entering the station name and pressing return, the coordinates of the station will be obtained from the database and displayed for reference.
You must also enter the height of the instrument axis above the station. The convention used is that distances measured from the station up to the axis are positive while distances measured from the station down to the axis are negative.
Foresight Station and Target Height
Enter the name of the station which will be used as the foresight station for this section of the traverse. Typically the foresight station should not exist in the database unless a resurvey is being conducted. After entering the station name and pressing return, the database is checked and if the station exists, the coordinates of the station will be obtained from the database and displayed for reference.
You must also enter the height of the target axis above the station. The convention used is that distances measured from the station up to the axis are positive while distances measured from the station down to the axis are negative.
level_area
All stations in a survey database are grouped by the level_area field so that it easy to reference stations in the same level/area of the mine. You must enter the level/area into which the new station/s being created by this function will be assigned. This is the same value that was entered on the Traverse Report Details form. The input field is included here so that you can easily change the level/area as the traverse progresses.
Backsight check
The backsight check is included to provide a way of entering check observations to the backsight station to confirm that the backsight station used is the correct backsight station. A distance and optional elevation check can be calculated and the discrepancy with the know horizontal distance and setup station elevation will be displayed. If the discrepancy is too great it indicates an error and the field measurements or backsight station name should be rechecked.
Check distance to backsight
Tick the checkbox to perform the backsight check.
Instrument used
Enter the instrument (as defined in the station errors table) used for the calculations. For explanatory information on the station errors table see here. This pick-list will be populated with the instruments from the station errors table. This field will only be selectable if BOTH of the following hold:
- A station errors table exists in the survey database
- Multiple instruments have been defined in the station errors table (ie there is a choice of instruments)
Vertical angles from Setup to Backsight
Enter the face left and face right vertical angles observed from the setup station to a target at the backsight station. Choose the Mean reverse angle button to calculate and display the average of all the entered vertical angles.
Slope distance
Enter the slope distance from the setup station to the backsight station.
Known horizontal distance
The horizontal distance from the setup station to the backsight station calculated from the coordinates stored in the database is displayed here when the Calculate backsight checks button is pressed.
Check horizontal distance
The horizontal distance from the setup station to the backsight station calculated from the entered slope distance and vertical angles is displayed here when the Calculate backsight checks button is pressed.
Distance error
The error between the known horizontal distance and the measured horizontal distance is displayed here when the Calculate backsight checks button is pressed.
Check backsight height
Tick this checkbox if the elevation of the setup station is to be calculated as part of the backsight check. This is a useful check to perform if there is a risk of subsidence at the setup station.
Backsight target height
Enter the height of the target above the backsight station.
Known setup elevation
The known elevation of the setup station from the database is displayed here.
Check setup elevation
The elevation of the setup station calculated from the entered slope distance, vertical angles and instrument and target heights is displayed here when the Calculate backsight checks button is pressed.
Elevation error
The error between the known setup elevation and the measured setup elevation is displayed here when the Calculate backsight checks button is pressed.
Horizontal angles
Two different methods of entering horizontal angle observations are provided. Depending on the method chosen, the required input fields will be made visible for data entry while the input fields for the other method will be blanked out. Choose the required method of horizontal angles as either:
- reiteration
Use this method of observing horizontal angles when using a theodolite which does not permit clamping of the horizontal circle to the upper plate of the theodolite. An example of this is the WILD T2 theodolite.
- repetition
Use this method of observing horizontal angles when using a theodolite which permits both the upper and lower plates of the theodolite to be clamped. An example of this is the WILD T16 theodolite.
Reiteration Angles
This method of horizontal angle observations requires that matching pairs of angles to both the backsight and foresight stations be recorded and entered into the input fields on the form. Typically a round of angles consists of face left angles to both the backsight and foresight stations and face right angles to the backsight and foresight stations.
If multiple rounds of angles are observed then the horizontal circle is often rotated prior to reading each new round to minimise errors due to horizontal circle eccentricity and graduation errors.
|
1. vertical circle 2. telescope 3. face left |
For efficient data entry the field book recording sheet for this method should look something like the table below:
| Face | Backsight | Foresight | Angle |
| Left | |||
| Right | |||
| Left | |||
| Right |
Each of the turned angles is calculated by the program so there is no need to enter each of the turned angles even though they will probably have been calculated by the surveyor in the field.
Repetition Angles
This method of horizontal angle observations involves the accumulation of repeated observations of the angle between the backsight and foresight stations from the setup station and then finally dividing the accumulated angle by the number of times it has been measured. This requires the use of a theodolite where the lower plate (the horizontal circle) can be clamped to the upper plate so that successive foresight angles can be established as the angle for the next backsight observation thus enabling the accumulation of the angle for each new measurement.
The sequence of measurements is typically:
- Set zero to the backsight station
- Measure the face left angle to the foresight station
- Clamp the horizontal circle
- Change face, sight to the backsight station and release the clamp on the horizontal circle
- Measure the face right angle to the foresight station (steps 3, 4 and 5 are repeated as often as required)
For efficient data entry the field book recording sheet for this method should look something like the table below:
| Station | Observed | Angle |
| Backsight | ||
| Foresight (face left) | ||
| Foresight (face right) | ||
| Foresight (face left) | ||
| Foresight (face right) |
Each of the turned angles is calculated by the program so there is no need to enter each of the turned angles even though they will probably have been calculated by the surveyor in the field.
Enter the observed angles into the appropriate input field and then choose the Mean Repetition Angles button or the Mean Reiteration Angles button to calculate and display each of the observed angles. This will also result in the mean horizontal angle being displayed.
After reviewing the calculated angles, use the outer scroll bar to scroll down to the data entry region for the vertical angles and slope distance.
Vertical angles
Choose the type of vertical angle observations which you wish to enter by using the selection browser to select either:
-
forward
Forward vertical angles measured from the setup station to the foresight station. Angles must be entered into the Forward vertical angles scrolling region. Enter each angle observation and then choose the Mean Forward Angle button to calculate and display the individual angles of elevation or depression and to also calculate and display the mean forward vertical angle.
-
forward & reverse
For lines of sight which are greater than 400m in length, it is generally good practice to observe simultaneous forward and reverse vertical angles to counter the effects of curvature and refraction.
This choice permits you to enter forward vertical angles measured from the setup station to the foresight station as well as reverse vertical angles measured from the foresight station to the setup station. Angles must be entered into the Forward vertical angles scrolling region and into the Reverse vertical angles scrolling region.
Enter each angle observation and then choose the Mean Forward Angle and Mean Reverse Angle buttons to calculate and display the individual angles of elevation or depression for the forward and reverse vertical angles and to also calculate and display the mean forward and reverse vertical angles.
Reverse heights
For best results the forward and reverse vertical angles should be measured simultaneously, or at least very close to each other in time and they should also be measured from the same setup by exchanging the target for the theodolite at the setup and foresight stations. There may be circumstances where this is not possible or where exchanging the target and theodolites results in a different instrument axis height. In these circumstances it will be necessary to use different heights and slope distance for the reverse vertical angles to those used for the forward vertical angles.
Use reverse heights
Tick this checkbox if the reverse vertical angles have been measured using different heights above the setup and foresight stations.
Reverse slope distance
Enter the slope distance measured from the new station (the station labeled as Foresight in the upper part of the form) to the original setup station. If a distance has not been measured just enter the same value as entered for the forward slope distance.
Height at new station
Enter the height of the instrument horizontal axis above the new station.
Height at original setup
Enter the height of the target above the original setup station.
Slope distance
Enter the slope distance measured from the setup station to the foresight station.
After all of the observation data has been entered, choose the Calculate Co-ordinates button to calculate the coordinates of the foresight station. The coordinates of the foresight station will be displayed in the display fields at the top of the form. When you are satisified that the entered observations and resulting coordinates are acceptable, choose Apply.
Use of the station errors table
If a station errors table exists in the survey database, information regarding the order of the new station may be displayed. For explanatory information on the station errors table see here. When calculating the vertical angle standard deviation and number of vertical angle observations to pass to the station errors table to calculate the new station order, Surpac uses the following approach:
- If you have just entered forward vertical angles, Surpac uses the standard deviation and number of these observations.
- If you have entered forward and reverse vertical angles, Surpac calculates the standard deviation and number of observations for the forward angles and the standard deviation and number of observations for the reverse angles, then uses the larger of these two standard deviations (and the corresponding number of observations) to pass to the station errors table.
If you have entered a single horizontal angle, a single vertical angle and a single slope distance then see here for more details of the information that is displayed by the station errors table. If you have entered multiple angles and/or slope distances then see here for more details of the information that is displayed by the station errors table.
The next stage in the processing displays the Review Surface Station Co-ordinates form.
This form is displayed to permit final review of the data for the foresight station before it is committed to the database. You may take this opportunity to enter or alter any of the data for optional fields which may exist in the database.
Complete the Review Surface Station Co-ordinates form and choose Apply to commit the foresight station details to the database.
After successfully saving the foresight station to the database, the SURFACE STATION TRAVERSING form will be displayed to permit the continuation of the traverse. This form will continue to be displayed to accept further observations until you choose Cancel.
Choose Cancel to discard the observations and calculations for the foresight station and to complete the SURFACE TRAVERSE function.
The observation data and a summary of the calculations can be saved in a variety of formats for reporting and for future audit purposes. An example of a note file produced by this function is shown below.
Note:This function will use the scale factor defined by the "scale factor" option of the defaults file when calculating the horizontal distance from the observed slope distance and vertical angles. This permits you to adopt a regional scale factor for the mine area if you find it necessary to make adjustments for the curvature of the Earth.