Overlap between scans and height of scanned objects

During a flight with TOPODRONE laser scanner, the ground surface is scanned with a certain width, called “scan”. The scan width is determined by the technical characteristics of the sensor, the operating altitude of the flight, and the terrain difference.
To perform correct post-processing of data from TOPODRONE laser scanners it is necessary that neighboring scans have common overlap. It is recommended to provide at least 30% lateral overlap to adjacent scans. Insufficient overlap between scans together with significant terrain differences can create an area without any data, which will significantly reduce the quality of output materials. When choosing a specific overlap value, parameters such as maximum laser beam length, scan angle (106 degrees on LiDAR for VLS) and height of the scanned object should be taken into account. To obtain optimal results when performing VLS with TOPODRONE laser scanners, it is recommended to use the following parameters when building a mission::

1	2	3	4				5
LiDAR model, Maximum beam length	Working height, m	Scan width, m	Distance between scan centers: % overlap, m				Maximum height of scanned object: % overlap, m
LiDAR model, Maximum beam length	Working height, m	Scan width, m	30%	40%	50%	60%	30%	40%	50%	60%
TOPODRONE HI-RES and 100 LITE	50	134	94	81	67	54	15	20	25	30
	60	160	112	96	80	64	18	24	30	36
	70*	140	98	84	70	56	21	28	35	42
TOPODRONE 200 ULTRA	100	267	187	161	134	107	30	40	50	60
	110	292	205	176	146	117	33	44	55	66
	120	320	224	192	160	128	36	48	60	72
	130*	260	182	156	130	104	39	52	65	78
	140*	280	196	168	140	112	42	56	70	84

Table 1. Dependence of the distance between scan centers on overlaps and working height.

Schematic of the main parameters of two neighboring TOPODRONE scans on the side projection.

The density of the received point cloud depends on such factors as: flight speed, flight altitude, surface reflectivity. As nominal initial values it is recommended to conduct flights at a drone flight speed of 6 m/s at a working altitude of 60 m for TOPODRONE 100 LITE, HI-RES and 120 m for TOPODRONE ULTRA with 40-60% overlap. Further changes of these parameters should be made taking into account the terrain, weather conditions and maximum height of scanned objects.