LINE Shift and drift parameters

Columns	format	content / meaning
1-4	A4	LINE                            (format free)
	I	Number of the flight line or another unambiguous number with not more than six digits.
	I6	Key with six digits Each digit is either Zero or One. Exactly six digits have to be indicated. The first three digits switch the shift and the last three digits the drift parameters on or off.
	F	Reference time (optional).

If the residuals of the GPS-measurements show systematic errors after adjustment, parameters have to be used for the corresponding photo strips to eliminate that systematics. The selection of the parameters required is facilitated by graphical demonstration of the residuals by means of the GPSview, REPLO or 3dView program (BINGO tools). Shift and drift parameters shall only be applied where the remaining residuals show the necessity. Otherwise the block will be weakened too much.

As soon as shift and drift parameters have been introduced for several photo strips, cross strips will be necessary if there are not enough control points.

The LINE statement in the GPS data file serves for introducing the shift and drift parameters. The LINE statements have to be added directly before each the first coordinates of a flight strip, or in the flight strip, if this is required by the residuals of the GPS-measurements. It does not make sense to switch one single shift or drift parameter, as e.g. only in X. Furthermore it will not make sense to choose the drift parameters without shift parameters. The best values for the key with 6 digits are therefore: ″111111″ and ″111000″.

The reference time defines that moment, when the drift is zero. For this reason the indication does only make sense when the drift parameters are applied. With this application the drift can be set to zero at any point of each strip. So the shift parameters of the single strips can be compared. If there is no reference time, the middle of the strip will be used instead.

The values of the drift parameters after adjustment have the unit ground ″units per minute″, if the time in the GPS data file is indicated in seconds. If the measurement unit in the object space is metre, the units are therefore metres per minute [m/min].

A ″*″ asterisk in column one or a negative standard deviation can be used to exclude the data for a single photo from the adjustment.

Attention: As the standard deviations are automatically copied from the prior line, if the following lines do not indicate standard deviations, a positive standard deviation has to be specified necessarily in the next line.