Control Points

Control Points are optional but if present must have X,Y values and a name.


[CONTROL]
PT=20,X=379786.194000,Y=6353362.100000,Z=98.159000,Name="pm13183",XYAcc="B2",ZAcc="LB",Active=Y
PT=21,X=379966.436000,Y=6353330.314000,Z=93.930000,Name="pm15402",XYAcc="B2",ZAcc="LB",Active=Y
PT=35,X=380133.408000,Y=6353427.744000,Z=92.756000,Name="ss7515",XYAcc="B2",ZAcc="LB",Active=Y

PT
Optional. This is the point number in the job that relates to the Control Point.
The control point may have a different XY value to the underlying point.
If a Least Squares Adjustment is run and the control point made active, the underlying point will adopt the control point coordinate.
If the control point is inactive, the underlying point will move as dictated by the adjustment.
So control point coordinates are "fixed" but the underlying point coordinates are not.

X
Mandatory. This contains the point Easting value or X co-ordinate in metres in the current zone (if used). Values are usually stored in the .acs file to six decimal places.

Y
Mandatory. This contains the point Northing value or Y co-ordinate in metres in the current zone (if used). Values are usually stored in the .acs file to six decimal places.

Z
Optional. This contains the point Height value or Z co-ordinate in metres. Values are usually stored in the .acs file to six decimal places.

Name
The name can be any text string and will enclosed by double quotes.

XYAcc
This is the control point XY accuracy value in metres.
If not present, the value is unknown.

ZAcc
This is the control point Z accuracy value in metres.

Active
This is a Yes (Y) or NO (n) value.
Y indicates that the control point is to be used in a Least Squares Adjustment.