I think it was something to do with Ordnance Survey mapping and was in an article in Swindon Heritage magazine.
Yep, seems so. If you scroll down a bit below the photo, there's this from the guy who posted it:
1953: The County Ground, Shrivenham Road, Swindon (OS "A Man with a Stick" series)
Source: Scan of an OS RP photograph.
Date: 1953.
Grid: SU1685.
Copyright: Ordnance Survey (OS)/Crown.
Used here by very kind permission.
Repository: Swindon Collection, Central Library.
www.swindon.gov.uk/swindoncollection
