If you can help me,I will be very grateful!

  																	   28th,oct,2003


Dear Mr./Miss,

	

	I am a student in China,and meet trouble when computing LST(land surface temperture) recently.If you know some can answer my question below,i will be very grateful!
　　First,i must input known emissivity (8-14um,or 10.5-12.5um) which I decide to derive it from noaa/avhrr ndvi.Sobrino(2000) supplied linear formula about ndvi>0 and emissivity,but he only involved ndvi(0-0.2),（0.2，0.5），（0.5，1）。
　　But to my surprice,after download avhrr/noaa ndvi data,I found ndvi:(-1,1),not (0,1).After searching,i understand that  -1 <= NDVI <= 0 means dry or wet surface without vegetation.But how can i establish the relationship between ndvi whose value is less than 0 and emissivity in band 10.5-12.5?

	If classify ndvi<0 as the following 4 kinds,how can I define a fixed value of emissivity (10.5-12.5)?
    (-1,-0.3),(-0.3,0.2),(-0.2,-0.1),(-0.1,0)   or
(-1,-0.2),(-0.2,-0.1),(-0.1,0)

    Is it true that ndvi<-0.2 means water?

	Or do you supply me some internet address about emissivity database?

	I am looking forward to your answer.Welcome to discussing with me.Thanks a lot!

	Please write in English.I am sure you can use it more skillful than I.


																Yours sincerely,
																	minnie




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