Reads in file content. Called from constructor. Does conversion GRID file's raw frequency data to log frequency.
Time axis is sampled regularly.
2nd dimension is non-regular sampled, but the same for all points in time. Otherwise it habits exactly like its parent class tsData1RFloat. Field content is assumed to be the dafault value for this field. Touching this field, deletes his default status and makes it beeing written as a normal Inventor node. See cqt3 and aqt2gridcompl for generating and converting this file format.