A GLTA is a detailed inspection of a tree from the ground, to look for features that bats could use for roosting. The aim of this survey is to determine if there are available roosting resources within the tree, to categorise the bat roosting suitability of the tree and to determine the need for further survey and/or mitigation.

A GLTA can be undertaken at any time of year, being most effective in winter months, when foliage is less likely to obstruct viewpoints.