[GRASS-user] Length of a political boundary

[ambijat]

Dear all,
I have a typical problem. I have extracted the raster boundary line from 
SRTM data. each cell contains the elevation value. Idealll\y speaking 
the total length of a boundary would be the some of the cells x cell 
resolution (90m). But, this is not true to actual boundary length as 
there are elevation in mountainous regions.

So, I need to add all the hypotenuse values of the cells. How can it be 
done any idea ?

Thanks!

regards,
Ambrish