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NDVI and LAI theory questions


mobgis

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I'm new to remote sensing and am trying to get my head around it all so apologies in advance for the noob questions. 

 

I've been playing around on envi and have produced some NDVI and LAI images- they look exactly the same but the value ranges are different what is the reason for this? Furthermore is anyone able to explain their relationship to me in easy to understand terms? (eg when LAI increases why does NDVI increase? 

 

Thanks :)

 

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  • 2 weeks later...

NDVI and LAI are positively correlated, just as NDVI and agricultural yields can be positively correlated.  This is what makes NDVI a useful proxy for modeling these types of biophysical relationships.  Unless you are actually sampling LAI in field plots, you're not actually developing an LAI that can be trusted (i.e., field collection vs. physical models).  Since sampling is labor and time intensive, the idea is to collect a statistically robust LAI sample throughout your region of interest, develop a statistical relationship between LAI and NDVI, and then extrapolate and model this relationship using NDVI derived from remotely sensed data.   Here's one of many papers devoted to this very subject: http://www.cof.orst.edu/cof/fs/turner/pdfs/turner_rse_1999.pdf 

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