[GRASS-user] Derivation of Landsat 8 Tasseled Cap coefficients for certain scene in Grass

[Nikos Alexandris]

* Kozlova Maria <kclo at yandex.ru> [2015-06-10 00:42:21 +0300]:

> Dear all,
> Asking for help in sudden difficult situation:
> I need to derive proper,  'personal', Tasseled Cap coefficients for some scenes of my study area. 
> I know, such procedure can be done by Matlab, but unfortunately, my colleague who could do this have now some troubles and cannot help me at the moment.
> 
> I need to do this work but can use only Grass. So is it possible to derive my own TC coefficients for each scene using Grass? If so, which modules should I use?

First, what is the plan to derive the custom coefficients?

> Is it possible to do image Tasseled cap transformation with these new coeficients?

Sure, as far as I understand, it's a simple sum. Something similar like (stolen
from the i.tasscap script):

r.mapcalc "output = k1 * in1band + k2 * in2band + k3 * in3band + k4 * in4band + k5 * in5band + k6 * in6band + k0"


> Am I right, that Grass module i.tasscap only provide TCT with use of
> standard TC coefficients (in the case of OLI images derived by M.H.A
> Baig et al, 2014)?

I quickly checked the numbers in the script and the paper by Baig 2014.
They are the same for *only* Brightness, Greenness, Wetness, TCT4. The
coefficients for TCT5, TCT6 are missing (compare the numbers in the
paper, page 428 with
<https://trac.osgeo.org/grass/browser/grass/branches/releasebranch_7_0/scripts/i.tasscap/i.tasscap.py#L86>).

Are these required?  They can be added quickly I think.

 
> Would be appreciate for any information

Hope the above helps a bit, Nikos