## Theory of Gap Fraction ##

### Summary ###

Gap Fraction is a crucial variable that governs interactions between light and vegetation and requires accurate modelling to predict light climate in the canopy, photosynthetic activity or canopy reflectance.


### Principle ###

The Gap Fraction (GF) is calculated using the following equation:
	<div align="center">
	<img src="../../ScreenShot/formula/Formula_GapFraction.png" height="60"></img>
	</div>
where n<sub>ground</sub> is the number of ground points and n is the total number of vegetation and ground points. Note that all LiDAR points with a normalized height lower than the user-defined height break (2m is commonly used) are treated as ground points in gap fraction calculation <a href="#1">(Richardson et al.,2009)</a>.


<div id="1"></div>

		@inproceedings{
		    author={Richardson J J, Moskal L M and Kim S H},
		    title={Modeling approaches to estimate effective leaf area index from aerial discrete-return LIDAR},
		    booktitle={Agricultural and Forest Meteorology,149: 1152-1160},
		    year={2009}
		}