Tree extraction using ALS data

Use a txt file for input and output. When using the code, Please follow:

1. Coarse extraction. 2. Thinning. 3. Refill

Note：

1.Thinning can be used for several times if you found that coarse extraction's result cointains too many noise points.

2.Refill can be used by many different ways and here is the simplest way to search the neighborhood