A parcel's charge is worked out from its size, so it goes under a dimensioner that measures it with lasers to the millimetre, and the volume is on the label and the bill. One parcel a week goes under the lasers and comes out with a volume larger than the box the lasers can see, and the scan image shows the box, and shows the shape the lasers measured, and the shape does not fit in the box.
I am the parcel hub's dimensioning technician, which is a job title that did not exist when I started.
How the dimensioner works.
The box goes along the belt under a frame with laser curtains, and the curtains measure it in three dimensions as it passes, to the millimetre. The system also photographs it from above, and the photograph and the measured outline are stored together, with the volume, for the customer's bill.
The measured outline is drawn on the photograph. On every parcel it is a rectangle round the box, tight, the way a chalk line is round a thing on the floor.
One parcel a week measures wrong.
The box in the photograph is a box, ordinary, brown, taped. The outline the lasers drew is bigger. Not by a millimetre. The measured shape is about forty percent larger in every dimension than the box it was measured from, and it is drawn on the photograph round the box, with air between the line and the cardboard on every side.
The volume on the label is the big one. The customer is billed for it.
What has been checked.
The lasers, calibrated with the reference block every morning, and they measure the reference block.
The belt speed, which affects the length reading, and which is logged and constant.
The parcel. I have taken the weekly one off the belt and measured it with a tape. It is the size in the photograph. I have put it back under the lasers by hand, slowly, and watched the curtains read it, and the readout shows the large size, and the tape in my hand shows the small one.
I have put a different box, the same size, under the lasers immediately after. It reads true.
The sender.
It is one sender. A business account, a small one, which sends one parcel a week through us, and every one of their parcels measures big, and no other sender's does.
Their address is real and the business is real and I have rung them, in the polite way you ring a customer to check a dimension, and the woman who answered said the box was the box, and that they had always been charged for a bigger one, at every carrier they had used, for thirty years, and had stopped asking.
The photographs.
I have a year of them. The outline the lasers draw round the box is not a rectangle, on close inspection. It is a rectangle with corners that are not square, a box that is slightly out of true in every image, in the same way, the way an old box is that has been used and reused and taped over the taping.
The photograph of the parcel shows a new box, square, clean. The lasers measure an old one, forty percent bigger, standing in the same place.
What is done about it.
The customer is billed for the measured volume, which is the rule, and they pay it, and have for thirty years, and I have made a note on the account that the dimensioning is disputed, and nobody has disputed it.
What I do.
I keep the lasers true.
The one thing I have changed is that I do not handle that sender's parcel.
I used to lift it off the belt to measure it by hand, once a month or so, for the file.
The last time, in the summer, I lifted it and it was heavier than a box that size should be, by a good deal, and it was not the weight of the contents, which the scale had already read. It was the weight of a bigger box. I set it down and put my hands on its sides, and the cardboard under my hands was old, soft, taped over the taping, and the box I was looking at was new and clean and square, and the one I was holding was not, and I let go of it and it went down the belt and under the lasers and they measured what I had held.