unit of grid size of s.class plot (ade4)?

Dear R-helpers,

I have perfomed a BPCA (dudi.pca, between, package=ade4) and visualised the result 
in a scatter plot (s.class, package=ade4). I would like to now the unit of "d" in the 
scatterplot, which represents the size of the grid in the background of the plot.
So to make it short, what is "d"?

thank you very much in advance, Heike


Heike Zimmermann
University of Halle/Wittenberg
Department of Botany
Am Kirchtor 1
06108 Halle 
Germany
+49 (0)345-5526264
http://www.geobotanik.uni-halle.de/index.en.php