Declaration: AppendExtData (ExtDataFName: string; Feedback: boolean): integer;
The function AppendExtData appends an external dataset to the existing dataset. It assumes that the external dataset has the same data structure (same spatial dimensions, the same number of time slots and the same calibration parameters for x, y and t) as the currently loaded dataset.

The parameter ExtDataFName specifies the filename of the dataset to be loaded (*.ilab). If the Feedback parameter is TRUE, a visual feedback during the loading of the external data is provided.

The function returns the following error codes:

 0 ... everything is OK
-1 ... the spatial dimensions do not match
-2 ... the numbers of timeslots do not match
-3 ... not enough spectral groups available
-4 ... memory overflow (external dataset is too big to be appended)
-11 ... wrong or undefined content type of the external meta data
-12 ... invalid property id(s) in the external meta data
-13 ... invalid date time format of the external meta data
-14 ... the specified data file does not exist
-15 ... the meta data fields of the external meta data are not properly sized