[GRASS-user] groups and subgroups

GRASS GRASS user
1

Hi all,
I'm a fairly new user to grass and am trying to test classify imagery
using unsupervised and supervised classification techniques, however
I'm looking for some clarification in grouping imagery using i.group.
My basic understanding is that a group is a set of imagery i.e RGB,
PAN, NIR ... what then is the subgroup?

The data that I'm analyzing is digital orthophoto acquired using
vexcel ultracam and has the following spectral resolution:

BLUE 390-470nm
GREEN 420-580nm
RED 620-690nm
NIR 690-900nm

I've import the files into grass with the following names

area1_cir_band1 (near infrared band) seperate dataset

area1_rgb.red
area1_rgb.green
area1_rgb.blue

I believe that after importing grass goups the RGB automatically

I then grouped all the datasets using i.group to area1_group

Is that correct? If so what is the subgroup?

Any information would be much appreciated

Cheers

--
Travis K.

Toronto, Canada
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"She knows there's no success like failure
And that failure's no success at all."
-Bob Dylan-
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2

Travis Kirstine wrote:

I'm a fairly new user to grass and am trying to test classify imagery
using unsupervised and supervised classification techniques, however
I'm looking for some clarification in grouping imagery using i.group.
My basic understanding is that a group is a set of imagery i.e RGB,
PAN, NIR ... what then is the subgroup?

Hi Travis,

You will find a much better answer than I could give in the GRASS
Imagery Manual (GRASS 4.0) by Harmon & Shapiro.

see section 10 "IMAGERY GROUPS" (p.25)

I have just generated a PDF version and put it up on the CVS server. It
will take a day or so to filter through to the website & mirrors, at
which point it will be available at: (227kb)
  http://grass.itc.it/gdp/imagery/grass4_image_processing.pdf

If you just can't wait, you can download it directly from the CVS web
interface:

http://freegis.org/cgi-bin/viewcvs.cgi/*checkout*/web/gdp/imagery/grass4_image_processing.pdf?rev=1.1&content-type=application/pdf

Hamish