Chain and Offset Survey
Chain and Offset surveys are typically used for pickups of underground drives or narrow stopes. This function enables you to input survey field data and the subsequent reduction to cartesian coordinates to form a string file. This file can then be recalled and used in the GRAPHICS module for further processing and viewing.
To run this function: Choose Survey > Underground surveys > Chain and offset, or...
Database Name
The current database name is displayed and cannot be changed in this form.
Define the Observation File
Enter the Location name and ID number of the observation file.
Data entry from
Describe the process of data entry. If the entry is keyboard input from a survey field book, then enter `K'eyboard. If the entry is from a file, then enter `F'ile. Usually file entry will come after data has been entered by keyboard, editing has occurred, and re-entry is required for further processing. The default value is `K'eyboard.
Complete the UNDERGROUND STOPE OR DRIVE PICK UPS form and choose Apply. If the `.str' or `.dat' file already exists the VERIFY CREATION OF A FILE form is displayed.
If you entered `F' to indicate the data entry is from a file, the UNDERGROUND STOPE OR DRIVE PICK UPS form is displayed. If you entered `K' skip this form.
Database Name
The current database name is displayed and cannot be changed in this form.
Define file to be recalled
Enter the Location and ID number of the file that contains the data, complete the form and choose Apply to continue.
Choose Apply to display another UNDERGROUND STOPE OR DRIVE PICK UPS form.
Database Name
This is the current database name and cannot be changed in this form
Define the Observation File Header Details
Enter the Purpose of Job in a manner that is beneficial to you when reviewing the report file. Enter the name of the persons involved in the survey (Surveyor), the Date, the Fieldbook name or number and the relevant Pages. You may leave these fields blank, as you are not required to define the file details.
Ups and Downs
Describe the measurement method of your ups and downs as either vertical ups or downs from the tape or line of sight, or perpendicular ups and downs to the slope of the tape or line of sight. The default value is vertical.
Perpendicular ups and downs are useful when surveying in a very steep raise as it is often easier to measure ups and downs perpendicular to tape.
It is important that you enter a value which agrees with the method of measuring the ups and downs otherwise the results will be incorrect.
Complete the UNDERGROUND STOPE OR DRIVE PICK UPS form and choose Apply, to display the UNDERGROUND PICK UPS - CHAIN AND OFFSET SURVEYS form.
Database Name
This is the name of the current database and cannot be changed in this form.
Set Up On Station
Station Id
Enter the station name of the occupied station. It is important the input is case correct.
Station to Instrument Axis
Enter the distance from the station to the instrument axis. Remember, measurements from the back (roof) to the instrument are -ve, and from the instrument to the floor are +ve.
Chainage, Offset
Enter the Chainage value and the Offset of the chain to the instrument station.
Foresight Station
Station Id
Enter the station name of the foresight station. It is important the input is case correct.
Foresight to Target Axis
Enter the distance from the station to the target axis. Remember, measurements from the back (roof) to the instrument are -ve, and from the instrument to the floor are +ve.
Chainage, Offset
Enter the Chainage value and the Offset of the chain to the target station.
String Number for Backs, String Number for Floor
The x y coordinates for each of the surveyed points and the elevation determined from the up or down measurement are assigned to a particular string. The string number assigned to the back coordinates has the default value of 51. The string number assigned to the floor coordinates has the default value of 1.
Complete the UNDERGROUND PICK UPS - CHAIN AND OFFSET form and choose Apply. If you enter a station name that is not found in the database, then a message will appear in the message window and the UNDERGROUND PICKUPS - CHAINS AND OFFSET form remains to re-enter the setup and foresight stations.
If the setup and foresight stations are not connected by virtue of the station_fr field of the foresight station a message is displayed in the message window and the CONFIRM FURTHER PROCESSING form is displayed. Choose Apply to accept the setup and foresight stations as entered and to then display the UNDERGROUND PICK UPS - CONFIRM STATIONS form.
Database Name
This is the name of the current database and cannot be changed in this form.
Set Up On Station
The occupied Station Id is displayed together with its coordinates gathered from the database.
Foresight Station
The foresight Station Id is displayed together with its coordinates gathered from the database.
Calculated Distance, Chained Distance
A distance check is carried out between the calculated distance from the stored station coordinates, and the chained distance laid out (with consideration to the offset distances and slope of the tape).
Choose Cancel to return to previous form for alterations.
Choose Apply to confirm the stations, and display the UNDERGROUND CHAIN AND OFFSET SURVEY form.
Database Name
This is the name of the current database and cannot be changed in this form.
Chainage, Offset, Up, Down, Break [Y/N]
Enter the chainage of the survey point, offset values, and up and down values that correspond to each chainage point. Breaks may
be introduced into the segments on either side of the drive by entering a `Y' in this prompt field. The following is an example of a chain and offset table of input:
| Point No. | Chainage | Offset | Up | Down | Break |
|---|---|---|---|---|---|
| 1 | 10.0 | -5.0 | 2.0 | 1.0 | N |
| 2 | 10.0 | 5.0 | 1.7 | 1.0 | N |
| 3 | 20.0 | -5.0 | 2.2 | 1.2 | N |
| 4 | 20.0 | 5.0 | 1.6 | 1.0 | N |
| 5 | 30.0 | -4.5 | 2.0 | 1.1 | N |
| 6 | 30.0 | 4.8 | 2.0 | 1.0 | N |
When you have finished entering data in the UNDERGROUND CHAIN AND OFFSET SURVEY form choose Apply to exit to the SURVEYING menu.
A new UNDERGROUND PICKUPS - CHAIN AND OFFSET SURVEYS form will be displayed with defaults to allow you to continue your chain and offset surveys with new stations. If you do not wish to continue choose Cancel.
Using an Underground Survey Database
Surveying in underground mines presents some unique problems caused by the frequent occurrence of very short lines of sight. The bearings which are subsequently calculated using the known station coordinates on these very short lines are likely to deviate significantly from the bearings obtained by successively adding the horizontal angles to the bearing from the setup station to the backsight station. To resolve this problem, the underground survey database has a field `rev_brng' in which the carried bearing is stored. Any survey function which accepts input of survey observations to calculate the coordinates of new points will use this stored bearing, if appropriate, to calculate the coordinates of the new points.
Note:The following discussion only has relevance if you are using an underground database. If you are using a surface database then bearings are ALWAYS calculated using the known station coordinates.
With respect to underground survey databases, connections between stations are defined by the contents of the `station_fr' field for each station in the database.
The following logic is employed by the calculation module to obtain the bearing from the setup station to the backsight station.
-
If no connection exists between the setup and backsight stations then
a form is displayed advising that the backsight/setup station pairing
may be unsuitable. The reason why the pairing may be unsuitable is that,
due to a mistake in recording the backsight or setup station names, there
may be no line of sight between the two stations due to intervening solid
rock. If this situation occurs the INCONSISTENT BACKSIGHT/SETUP
STATION COMBINATION form is displayed.
Choose Apply to obtain the bearing from the setup station to the backsight by calculating it from the known coordinates of the stations.
Choose Cancel to abort the coordinate calculation process completely. You would make this choice if you wish to check on the backsight and setup station names before proceeding.
- If a connection between the setup and backsight stations exists, then
the stored bearing from the database and the calculated bearing obtained
by using the known coordinates of the two stations are compared.
If the difference between the bearings is less than 2 minutes then the calculation of coordinates will continue and the stored bearing will be used.
If the bearings differ by greater than 2 minutes then the INCONSISTENT DATABASE REVERSE BEARING VALUE form is displayed.
The stored and calculated bearings between the setup and backsight stations are displayed. You must choose one of three possible actions by choosing the appropriate button to determine how you should proceed from this point.
Choose Use stored bearing to proceed with coordinate calculations using the bearing obtained from the database as the bearing from the setup station to the backsight station.
Choose Use Calculated bearing to proceed with coordinate calculations using the bearing obtained from the known coordinates of the setup station and the backsight station.
Choose Cancel to abort the coordinate calculation process completely. You would make this choice if you wish to check on the backsight and setup station names before proceeding.
If the point being surveyed is a new survey station, the reverse bearing from the new survey station to the station from which it was surveyed is stored in the rev_brg field.
Messages
``n'' points written to file filename#.str
Result
The function underground chain and offset survey has formed an `.str' file of the observations. A `.dat' file has also been formed containing all the data input, and this one is preferred if wanting a hardcopy.
If the data has been entered incorrectly, the `.dat' file may be edited using a text editor. This avoids having to re-enter the data.