They chose to work you or not. Some days they will and some days they will send you home with a hour pay. When they assign you a line some time you will stay with that line and other times you will be moved to a different line.
Poor management with low understanding of what surveyors really do in real world. Run as a money factory with no bonus or decent benefits. lots of long work days were often followed by months of uncertainty and no pay coming in.
high pay during busy periods
long hours, management intentionally forgets booked days off