A transect moves through the survey area at a fixed bearing, and every tree with a DBH above the threshold gets assessed. The discipline of the transect method is that it removes selection bias — you can't subconsciously walk toward the impressive old grey box and away from the younger material that's harder to assess. Every tree in the corridor gets a record, good, poor, or uncertain.
Transect as the Audit Framework
Transect and Tree ID create the spatial reference system that anchors every assessment to a recoverable location within the survey area. A tree assessed on Transect 3, ID T3-047 is findable on the survey map and re-examinable if the initial assessment was made under poor visibility conditions or if the tree's status changes between survey rounds.
Species with Diameter, Tree height, and Crown Width establish the biophysical profile. In eucalypt-dominated vegetation communities, the combination of species and diameter class is the primary predictor of hollow availability. Box-ironbark country with DBH thresholds above 40cm produces a very different HBT density than young regrowth on disturbed soils where the structural complexity that generates hollows hasn't had the decades to develop.
Hollow Morphology
HBT form, Hollow type, and Hollow size capture the morphological classification. HBT form describes the overall tree structure — basal hollow, trunk hollow, branch hollow, composite. Hollow type describes the specific formation mechanism: spout hollow formed by a broken branch, mast hollow from top dieback, pipe hollow from longitudinal decay. Hollow size — small, medium, large — maps to the functional categories used by wildlife management frameworks.
The morphological classification matters because different hollow types have different habitat qualities. A deep pipe hollow in a standing dead tree provides a dramatically different microclimate than a shallow spout hollow in a living tree with an active canopy. A micro-bat species that thermoregulates using ambient temperature variation needs a different hollow profile than a python species requiring stable deep-chamber temperatures.
Definite Hollows versus Potential Hollows — the confirmed-versus-suspected distinction — determines the assessment confidence level and the level of follow-up required. Potential hollows in trees with otherwise high habitat value are the records that generate the targeted inspection recommendations in the final survey report.
Target species against Status is the regulatory conclusion. A tree assessed as retaining confirmed large hollows with a target species list including Schedule 2 fauna doesn't get incorporated into a development footprint without formal approval and offset, regardless of where the clearing boundary is drawn.