[GRASS-stats] Re: [GRASS-user] Testing i.pca ~ prcomp(), m.eigensystem ~ princomp()

[Nikos Alexandris]

On Tue, 2009-03-31 at 17:13 +0200, Markus Neteler wrote:
> On Tue, Mar 31, 2009 at 5:00 PM, Markus Metz
> <markus.metz.giswork at googlemail.com> wrote:
> > Nikos Alexandris wrote:
> >> Using MODIS (range varries between bands, up to max. ~5500):
> >>
> >
> > Sure? Valid range: -100 - 16000 for MODIS e.g. Surface Reflectance 8-Day L3
> > Global 500m.
> 
> Remember that you have to rescale these data first:
> 
> https://lpdaac.usgs.gov/lpdaac/products/modis_products_table
> -> MOD09Q1  	Terra  	Surface Reflectance Bands 1–2  	Tile  	250m  	8 Day
>     https://lpdaac.usgs.gov/lpdaac/products/modis_products_table/surface_reflectance/8_day_l3_global_250m/v5/terra
>    -> layers
> 
> ... MULTIPLY BY SCALE FACTOR ...

> best,
> Markus

Yep, I know that. But why is it wrong to just use them as they are?
Regards, Nikos