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GEOVIA Surpac

EDM survey

This function is used to reduce hand booked EDM surveys to co-ordinates. Observations are entered in rounds from a given survey station. The reduced co-ordinates are saved to a string file.

To run this function: Choose Survey > Surface surveys > EDM survey, or...

In the Function Chooser, type EDM SURVEY, and press ENTER.

Define the .DAT and .STR file to create.

Enter the Location name and ID number of the file to be created.

The '.dat' file is used to record entered observations for later correction if necessary. The '.str' file will contain the co-ordinates of the entered points.

Purpose

Enter a brief description to help identify the file. This will be written to the header record of this file.

Process existing file

For Keyboard entry you must enter 'N'. After the completion of data entry all set-up and observation are saved to a file (Loc)(Id).dat for future reference.

Enter `Y' to reprocess an existing `.dat' file.

Vertical circle zero

Enter the zero position of the vertical circle if vertically above `zenith', vertically below `nadir'.

Vertical circle face

Enter if the observations are taken with face 'left' or face 'right' angles.

Complete the ENTER EDM SURVEY OBSERVATIONS and choose apply to display the DEFINE THE BACKSIGHT AND SET-UP STATIONS form.

Backsight

Enter the name of the backsight station that was used for this set-up.

Reference angle

Enter the reference angle used for this set-up. This allows entry of field observations with a non zero backsight. The angle must be in the format described below:

If you have selected DEGREES as your Angle units, the angle must be entered in DDD.MMSS format.
If you have selected GRADS as your Angle units, the angle must be entered in GRADS to four decimal places.

Set-up

Enter the name of the instrument station that was used for this set-up.

Instrument height

Enter the height from the station to the instrument axis.

Note:If the instrument axis is above the station the height must be '+', if the instrument axis is below the station it must be `-'.

Surveyor

Enter the name of the person who completed the survey. This value will only be used if you choose to nominate one of the surveyed points as a new station, in which case it will be stored in the survey database where it can be used for audit purposes.

Survey Date

Enter the date of the survey. The date must be entered in the form YYYY-MM-DD HH:MM:SS, although the HH:MM:SS part is optional, eg 2003-10-23 10:20:33 and 2003-10-23 are both acceptable values. This value will only be used if you choose to nominate one of the surveyed points as a new station, in which case it will be stored in the survey database where it can be used for audit purposes.

Complete the DEFINE THE BACKSIGHT AND SET-UP STATIONS form and choose apply to display the ENTER OBSERVATIONS FOR EDM SURVEY form.

Backsight

The name of the backsight station is for display only.

Set-up

The name of the set-up station is for display only.

Reference angle

The reference angle is for display only.

Instrument height

The instrument height is for display only.

String

Enter the string number of the observed point. If you wish to introduce a break into the string enter `0', otherwise use a positive integer no greater than 32000.

Prism

Enter the height of the prism to the observed point.

Note:The height must be `+', if the instrument axis is below the station it must be `-'.

Slope distance

Enter the slope distance measure to the observed point.

V.angle

Enter the observed vertical angle. The angle must be in the format described below:

If you have selected DEGREES as your Angle units, the angle must be entered in DDD.MMSS format.
If you have selected GRADS as your Angle units, the angle must be entered in GRADS to four decimal places.

H.angle

Enter the observed horizontal angle. The angle must be in the format described below:

If you have selected DEGREES as your Angle units, the angle must be entered in DDD.MMSS format.
If you have selected GRADS as your Angle units, the angle must be entered in GRADS to four decimal places.

Description

Enter a relevant description for the surveyed point.

OFFSETTING POINTS FROM THEIR SURVEYED POSITION

If necessary, it is possible to offset a point from its surveyed position. This is often necessary when a point is either in a position which is too dangerous, or in a position which is inaccessible.

In situations such as these it is possible to enter a code as part of the point description which will offset the surveyed point to its desired location.

The point offset information is entered into the description field in the form

D-/+n.nn O-/+n.nn V-/+n.nn

where D indicates a distance offset along the line from the set-up station to the surveyed point with `+' indicating an increase in the horizontal distance and `-' indicating a decrease in the horizontal distance.

Note:This will not alter the elevation.

O indicates a perpendicular offset from the line between the set-up station and the surveyed point with `+' indicating an offset to the right of the line when looking from the set-up station to the surveyed point, and, `-' indicating an offset to the left of the line.

V indicates a vertical offset from the surveyed point. `+' indicates an increase in elevation and `-' indicates a decrease in elevation.

n.nn is the distance which is to be used as the offset value.

The letters which are used to indicate the offset direction MUST be uppercase, a point description can be added after the codes.

For example,

D+2
			V-1.4 O-1
			O+2 V+2 D-1

Using underground type stations

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, underground type stations use 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 underground type stations. If you are using a surface type stations then bearings are ALWAYS calculated using the known station coordinates.

With respect to underground type stations, 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.

Nominating surveyed points as Stations

A survey of an area may be carried out more efficiently if you nominate surveyed points as temporary or low grade survey stations for subsequent setups during the course of a survey. This is possible by including a station identification code in the point description field of the point which is to be used as a survey station.

To identify a point as a survey station enter something like `STNABC' in the point description. The `STN' indicates that the point is to be used as a survey station and saved to the survey database. The characters after `STN', in this case `ABC', are used as the identifier for the new station.

Note:When the calculations for the new station are performed you are given some options regarding the creation of the new station. This is done via the Store New Station As Surface or Underground Station? form:

Store New Station As Surface or Underground Station form

Station

This is an informational field that displays the name of the new station being created.

Store as surface or underground station?

Do you want to store the new station as a surface or underground station? See here for details of the difference between surface and underground stations.

Press Apply on this form to continue processing this station, or Cancel to cancel processing of this station.

Use of station errors table: If a station errors table exists in the survey database, information regarding the order of the new station may be displayed. See here for more details.

Complete the ENTER OBSERVATIONS FOR EDM SURVEY form and choose Apply to display the DEFINE THE BACKSIGHT AND SET-UP STATIONS form. If you do not have another EDM SURVEY choose Cancel and return to the SURVEYING menu.

Result

The observations are saved to a '.DAT' file for later editing if necessary and the co-ordinates of the observed points are calculated and saved to a '.STR' file.