where/how to check an old 30m surveying tape?

That seems to be Olympic swimming pool size.

Local running track? At least ones used for competitions should be accurate. They also have measuring tapes as used for long jump etc you could compare against.

I passed a parked up 40 foot container lorry and realised there must be an international standard for them. I'd liked to have seen the applicable temperature on the drawings but 3 tech drawings from 3 companies on 3 continents the same numbers. External dimensions for stardard 40 footer, from moutnting box to box,

In message <10dcr5e$3tha2$ snipped-for-privacy@dont-email.me, N_Cook snipped-for-privacy@tcp.co.uk> writes

Yes, but pre welded rail was laid with gaps to allow for expansion, so best to measure on a cold day. At least we are approaching to best time of year for that :-)

What are the tolerances on those figures? Assuming that '40 foot' to be accurate to 4 or 5 significant figures would be wildy optomistic.

All 3 were very professional looking wwww tech drawings , not copy and paste, from some original international shipping organisation. For my purposes as long as the 40 foot was accurate to +/-1cm 'scuse mixed units,wouldbe ok. Over time measuring numerous containers with the sametape ,and tension of course, should show how consistent. And assuming the"boxes" had notbeen obviosly bashed anddistorted.

Find someone with a new one?

N_Cook snipped-for-privacy@tcp.co.uk> wrote in news:10dcr5e$3tha2$ snipped-for-privacy@dont-email.me:

Get a 15quid Lidl laser measure next time the are on sale (currently only on the Irish site) and compare the result:

They're useful things to have around anyway.

I own a 50m range one, excellent on repeated readings for the same temperature, but I would not rely on its absolute accuracy. I was going to adapt for a "side scan" tidegauge for a tidal river site that is only reached at high tides , to extend the monitoring time to mid river andall tides. But the reflection off water at only 10 degrees or so , needed the return sensitivity beefed up and/or more send power. Got the "cat toy" "laser" led gixmos to parallel up on the send side and a cheapo reflecting telescope for the receive but Ilot interest. I managed to decode the internal LCD drive signal to pass the main data to a serial link though. It would probably have only worked at night over 50m , not in sunlight.

I've a 30m cloth tape. Checked it with a 5m Stanley steel tape that had been checked with a v. high quality steel ruleer. Generaly 20C is the temperature on steel rulers.