Hi,
The formula to compute the mean would look like :
"avg(im1b1,im1b2,im1b3,[...],im1b12)"
Once you have produced the image containing the mean values, you can use
it back in the otbcli_BandMath.
Lets say you set the input image list parameter "il" to :
- first image : the 12-band initial image
- second image : the mean image
The formula for std dev. would look like :
"sqrt(avg(
(im1b1-im2b1)*(im1b1-im2b1),(im1b2-im2b1)*(im1b2-im2b1),[...],(im1b12-im2b1)*(im1b12-im2b1)
))"
Regards,
Guillaume
Le 03/09/2014 17:43, dcd a écrit :
Hi Julien,
I was just re-reading this post as it's referenced on
gis.stackexchange.com
<http://gis.stackexchange.com/questions/88996/per-pixel-statistical-calculations-on-a-raster-stack-using-gdal/111103#111103>.
I noticed I missed something in your answer:
On Tuesday, 11 March 2014 03:54:21 UTC-4, Julien Michel wrote:
2) Regarding your second question, it depends on what you intent
to calculate : the mean and std dev of one layer, or the mean and
std dev of one pixel accross several layers ? The latter is
already possible (you just need to write the mathematical
expression), while the former again requires more code on OTB side
(but it would be useful to be able to call std(im1b1) for instance
in a formula).
The intent was to calculate the mean and std. dev. of a single pixel
across several layers. Ideally, I'd like to calculate the cv of each
pixel. The reply above appears to indicate that this is already
possible within OTB. If so, how would you write the expression using
otbcli_BandMath given a multilayer image (e.g., 12 bands?).
In other words, if I had a 12 band image of average monthly
temperature, how would I calculate the mean (or std.dev., or cv) of
each pixel across several layers using otbcli_BandMath?
Thanks!
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