Monday, September 23, 2013

Modelling canopy cover with satellite data


Great news: there’s a new canopy cover article online!

I’ve tested plenty of different methods for estimating canopy cover, but the test with satellite images that was supposed be part of my doctoral thesis was delayed and delayed. I guess that I was still busy with other things on the day when Janne sent me an excel file with the SPOT 5 reflectances from our Hyytiälä sample plots. Out of curiosity, I calculated the RSR spectral index from the reflectances and plotted the values against the lidar-based canopy cover estimates that I had. Surprisingly, it was a really beautiful exponential curve! The earlier results that I had seen from the boreal zone were not nearly as impressive. I think that the reason for the very good accuracy was that we used lidar-based canopy cover estimates instead of quickly measured, inaccurate field values.

So nice!

It still took more than a year until I finally started writing the paper last winter in Norway. I tried to keep things simple – one problem, one data set for modelling and another for validation, and two spectral indices to compare. After some reviews, the paper was accepted quicker than I thought. It is always nice when you can keep things simple, but unfortunately all of our problems are not as easy. 

Hyytiälä from satellite

1 comment:

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