The research of the gap probability of forest canopy has been donefor three decades.Two methods

radlative transfer and geometric optics

have beenused seperately in the research of modeling gap probality

and both lead to impor-tant results.This paper is focus on the combination of the two methods so as todevelop a hybrid model.to check the new model

it is important to obtain experi- ment data

so we make the measurement carefully

and create some new ways formeasurement

for example

“method of photography”

“method of parallel light”

which both are economical and convenient methods.