Vector Type and Column Order

CT / RECT

If the parameter RECT appears on a #Units directive, the three basic numbers that define a vector are assumed to be the true north-relative East-North-Up displacements of the TO station with respect to the FROM station.  Otherwise, they are the Distance, magnetic Azimuth, and Vertical angle measurements of a compass and tape (CT) data line.  In either case, the first two tokens on a line are the FROM and TO station names.  The third token is the first of the three primary measurements, the order of which is specified by the Order parameter as described below.  See Vector Data Lines.

Order = DAV / DVA / ADV / AVD / VDA / VAD / DA / AD

Order = ENU / EUN / NEU /NUE/ UEN / UNE / EN / NE

The first form applies to subsequent compass and tape (CT) data lines, where the three primary measurements (distance, azimuth, and vertical angle) are assumed to be in the column order indicated by a permutation of the letters D, A, and V. The initial default is DAV.  The shortened sequences (AD and DA) can be used to specify that the vertical angle will be omitted entirely from the set of measurements -- a useful option for underwater surveys in particular. The effect is the same as specifying zero for the vertical angle.

The second form specifies the order that the East-North-Up coordinates appear on  both #FIX directives and RECT data lines.  The initial default is ENU.  Like the vertical measurement on CT lines, the Up coordinate can be omitted if one of the two shortened sequences is specified. When geographical coordinates are being entered for fixed stations, "order=ENU", for example, specifies that the column order is longitude - latitude - elevation. See #Fix Directive.

Both forms of the Order parameter can appear on the same #Units directive since they apply to different kinds of data that might follow.

CT data lines can optionally have up to two additional measurements: a vertical adjustment, or an instrument height followed by a target height.  Their order and position on a data line, however, cannot be specified.  (If present, they always follow the DAV measurements.)  For more information, see Vector Data Lines.