density of forest cover was once assessed by counting the patches of sunlight that came through the canopy. A lot has changed since. Satellite mapping, visual interpretation of that imagery digitally presented
Links:
[1] http://admin.indiaenvironmentportal.org.in/opinion/dense-cover
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/down-earth
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/forest-resources
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/forest-research