comp.lang.idl-pvwave archive: archive » Re: Rescaling byte (0-200) ndvi to -1 to 1 values

Home » Public Forums » archive » Re: Rescaling byte (0-200) ndvi to -1 to 1 values

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Rescaling byte (0-200) ndvi to -1 to 1 values [message #80863 is a reply to message #80861]

Thu, 19 July 2012 12:19

Narnia
Messages: 5
Registered: July 2012

Junior Member

Thanks a lot, Paul, that makes sense of course but (I'm a real beginner with IDL), I'm still not sure how I would implement that as far as calling in the images and declaring that to run and scale all the images in my folder! :(

On Thursday, July 19, 2012 9:18:39 PM UTC+3, Narnia wrote:
> I'm using the eMODIS 10-day product from the USGS with this description: "MODIS NDVI data are stretched (mapped) linearly (to byte values) as follows:
> [-1.0, 1.0] -> [0, 200]
> Invalid Values: 201 - 255
>
> NDVI = (value – 100) / 100; example: [ (150 – 100) / 100 = 0.5 NDVI ]"
>
> I am trying thus to scale the data in ENVI just using Band Math [expression:((b1-100)/100)] and all the values I get are 0 across my entire image. Any thoughts as to why?
>
> Secondly, I need to do this for over 400 images; can someone suggest a quick script that can read and scale this data in IDL? I tried 'ScaledImage' but i keep getting errors as well...
>
> Thank you so much!

Report message to a moderator

[Message index]

		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Narnia on Fri, 20 July 2012 07:01
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Narnia on Fri, 20 July 2012 07:05
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: David Fanning on Fri, 20 July 2012 06:07
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Narnia on Fri, 20 July 2012 06:03
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Paul Van Delst[1] on Thu, 19 July 2012 13:13
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Narnia on Thu, 19 July 2012 12:19
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Paul Van Delst[1] on Thu, 19 July 2012 11:41
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: k.shemsu on Mon, 20 May 2013 05:39

Previous Topic:	Speeding up xy distance calculations using complex numbers
Next Topic:	Re: IDL8 plot

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Fri Oct 24 14:10:00 PDT 2025

Total time taken to generate the page: 3.12139 seconds