Crowle was one of the triangulation points in the first and second triangulations of Great Britain. ‘Crowle Beacon’ was used in both 1806 and 1842.
In the 1806 survey station was described thus “Сrоwle station is situated about half a mile east from the village of Crowle in Lincolnshire It is on a rising ground where once stood a windmill There is now a mill nearly two hundred feet east of this station it can be easily found”
The location of the survey station at ‘Crowle Beacon’ was calculated to be 53°36’36″N, 0°49’4″W – note that these coordinates are based on the original Airy Coordinates which are different to those used in GPS etc. [This explains it all should you need to know the detail – https://www.ordnancesurvey.co.uk/docs/support/guide-coordinate-systems-great-britain.pdf]
It would appear that the location of this survey station was at the top of Crowle Hill where Kingsthorpe Villa is now located. This was the site of the East Mill, though the West Mill would be west of the mill and not east of it as described above.
Reference – An Account of the Trigonometrical Survey, Carried on by Order of the Master-General of His Majesty’s Ordnance, in the Years 1800-1809 – https://books.google.co.uk/books?id=0e9eAAAAcAAJ&lpg=PA169&dq=%2B%22crowle%20beacon%22&pg=PR1#v=snippet&q=%20crowle&f=false
A second triangulation was undertaken in 1842 and the station was described thus “Crowle Beacon 1806 This station was situated on a barrow where once stood a windmill nearly 150 feet east of a mill The station was 36 9 feet from the corner of the hedge next the road and 43 9 feet from the road the barrow has however lately been removed and with it every trace of the old station” – This seems to correctly suggest that it is the survey station that is east of the mill.
The triangulation from Crowle in 1842
It seems incredible that they were able to take sightings on Great Whernside and Lincoln Minster. Ordnance Trigonometrical Survey: Principal Triangulation – https://books.google.co.uk/books?id=H2dCAQAAMAAJ&dq=ordnance%20survey%20triangulation%20misterton%20carr%20base%20crowle&pg=PA100#v=onepage&q=crowle&f=false