a ojo

How could I translate ' a ojo de buen marinero'? rule of thumb?

The full sentence:
Los mapas se construían por rumbos de brújula y distancias a estima “del ojo de un buen marinero”

My attempt:
The charts were constructed by courses of compass and distances considered by“ the eye of a good sailor”.
or
The charts were constructed by courses of compass and distances considered by“ the rule of thumb”
I don't like them at all, so would you be son kind and help me. Thank you.
http://http.cdnlayer.com/wordreferen...tons/quote.gif

“Eye of a good sailor” es correcto. Lo que no es bien entendido es “rumbos”. Los puntos que indican las brújulas son “bearings”.

The maps were constructed using compass bearings with distances estimated by the eye of a good sailor.

Since we are talking about compasses, maps and charts, what about the following sentence?
las otras cuatro presentan la misma estructura: el centro de cada circunferencia directriz de dieciséis nudos de vientos de 282 milímetrosde diámetro

My attempt:
the other four display the same structure: the center of each directive circumference of sixteen wind knots of 282 millimeters of diameter

about 'nudos de vientos', you can see them on the map: http://fglorente.org/mapas/bajares/JoanMartines2.gif

No soy ningún experto. Según este enlace, los círculos son “windroses” Portolan Charts . Es una palabra nueva para mi.

A lo mejor: the other four display the same structure: each windrose has sixteen points and a diameter of 282 millimeters.

Thanks for the link!

We find in it rhumb lines and its definition, but I don't find rhumb in my dictionary. I suppose it means course...

Claro, o los puntos de una brújula, pero no es una palabra común. A mi me parece es mejor decir “compass point” o “course on a single bearing” o simplemente "straight line".