How isoglosses are used to establish regional dialect areas?

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Clarification of Question by dashtekahe-ga on 22 Feb 2006 19:50 PST

Hi there
My question is related to sociolinguistics.

"An isogloss is the geographical boundary of a certain linguistic
feature, e.g. the pronunciation of a vowel, the meaning of a word, or
use of some syntactic feature. Dialects are typically demarcated by
whole bundles of isoglosses, e.g. the Benrath line that divides High
German and Low German; or the La Spezia-Rimini Line which divides the
eastern Romance languages from the western ones."
en.wikipedia.org/wiki/Isogloss

Once the area of a dialect has been determined, the isogloss is the
border around that area or the line separating it from areas of other
dialects.

This is just a free comment.

HI Dash,
Yes, of course.
It is my understanding that isoglosses are not used to establish
regional dialect areas, but rather that after the area in which a
dialect is prevalent has been established by linguistic research of
how the people there talk  - as different from the way those in
surrounding areas do -  then the isogloss is the dividing line between
these areas.  Its definition must follow the linguistic research, thus
it cannot be said that it is used to establish the areas.  Once the
areas have been established, the isoglosses mark the lines between
them.

I expect that the linguists develop a rough idea of where the dividing
line is and then refine it as their research continues.

Maybe I am reading your statement of your question differently than
you meant it.  I hope my explanation is of some use.

Regards, Myoarin