LiDAR or photogrammetry: choosing correctly the first time

This choice gets over-complicated. In practice it collapses to a single question: is there vegetation between the sensor and the ground you need to measure?

Photogrammetry measures what the camera can see

If a camera cannot see the ground, no amount of processing will recover it. Over canopy, photogrammetry returns the top of the trees. Software that claims to produce bare earth beneath dense vegetation from imagery is interpolating between whatever ground it could see - which on a wooded site may be nowhere near where you need levels.

LiDAR measures distance directly

A laser pulse can produce several returns. Some slip between leaves and strike the ground. That is the entire advantage, and on a vegetated site it is decisive.

Where photogrammetry wins

• Open ground - it is cheaper, faster and produces genuinely useful colour imagery
• Anything where visual interpretation matters: progress documentation, defect inspection, marketing
• Stockpiles and earthworks on clean sites, where 1-2% volume accuracy is routine

Where LiDAR wins

• Corridors: transmission lines, railways, canals, roads through vegetation
• Forest, plantation and tea estate terrain
• Flood modelling over vegetated floodplain, where canopy-as-ground is a serious error
• Any site where the difference between canopy top and true ground would corrupt an earthwork quantity

The hybrid answer

Plenty of sites need both: photogrammetry over the open majority, LiDAR over the wooded portion. Anyone who tells you their single preferred method suits every site is describing their equipment, not your requirement.