Chart scale

[in irons]

On all Leisure Editions of Admiralty Charts there is a printed scale usually on a land area showing (on the one I am looking at) Sea miles and feet.

Can you please explain to me how those scales are intended to be used and how does that work with the inherent distortions created by a Mercator projection

[StuM]

Exactly the same way you use the vertical degrees latitude markings on the sides of the chart, only the scale is displayed horizontally. The "distortion" is irrelevant.

[in irons]

Thank you for your reply

[El Pinguino]

That scale is often found on harbour plans where 'minutes of arc' on the margin don't give the convenient accuracy of the scale you speak of.

Another interesting thing about harbour plans is that they often use transverse mercator projection rather than standard mercator....

https://en.wikipedia.org/wiki/Transv...tor_projection

Too much information???

[tkeithlu]

In the area covered by most charts the error from one end of the chart to the other in a mercator projection, transverse or otherwise, is negligable.

[El Pinguino]

Originally Posted by tkeithlu

In the area covered by most charts the error from one end of the chart to the other in a mercator projection, transverse or otherwise, is negligable.

Dunno about that... define 'most'

It is always good practice to lift off distance adjacent to where you measured it...

[tkeithlu]

I have charts like that. Two of them. One the Gulf of Mexico from Cuba north and the other the eastern seaboard and Bahamas. I have hundreds covering much smaller areas. That's what "most" means.