Topband: 160m activity and propagation

[Roy Morgan]

Dave,

Thanks for your reply. I am reminded that here I may have topographic maps from late 1800's possibly and from the late 1950's. I will dig them out to see what they show. 

I assume the numbers you show are for London. Also I'd expect to find accurate current values for my location on line somewhere. 

It's just of interest - I don't expect to do any important surveying with this Brunton Pocket Transit. I do want to survey our house lot. I think only one corner pin is known.  

I used to work at NIST/NBS Gaithersburg, MD. On the grounds there is a primary survey monument. It is at the top of a 20-foot(?) pole anchored in bedrock and covered by an innocuous cover in the grass. It and perhaps 2 or 3 others in this part of the country establish the basis for all surveying this side of the Mississippi. It's position is known to a small fraction of an inch.  Also on the site is a GPS monitoring system that issues corrections to GPS users doing surveying. In that same building is the US standard 1.1 million pound weight.  

Ferdinand Hassler was Superintendent of the first thorough survey of the East coast sometime around 1800. See NIST.gov for info about him. 

Roy Morgan
K1LKY Western Mass

> On Feb 21, 2020, at 9:39 AM, David Olean <k1whs at metrocast.net> wrote:
> 
> Years ago, I think the correction was more like 17 degrees in New England.   ...magnetic variations for London, England over the last few  centuries. The pole really does move.
> 
> YEAR   DECL.
> 
> 1600  8E
> 1650  1E
> 1700  7W
> 1750  18W
> 1800  24W
> 1850  22W
> 1900  16W
> 1950   8W
> 1970  7W
> 
> 73
> Dave K1WHS