Lidar

Question 1

Define LiDAR

What does it do?

Answer 1

Light Detection and ranging

Uses the speed of light to calculate range from transmitter to target and back to receiver.

Question 2

LiDAR System - Laser Scanning

Answer 2

• High pulse rate – 50 to 250 khz variable;
• Operate in the NIR range for terrestrial systems and in blue-green and NIR for marine;
• Range (height) from 05-15cm (can be more)

Question 3

What is the footprint of the LIDAR Beam?

Answer 3

•The footprint of the LiDAR beam is the DIAMETER of the circle of light that intersects with the reflecting surface

Question 4

LIDAR Footprint Size

Answer 4

The footprint size represents the SMALLEST UNIT OF RESOLUTION of the signal.
- discrete system the footprint size is typically 10-30 cm

Question 5

Size of Waveform Footprint VS Discrete Footprint

Answer 5

Wave Form > 1m

Discrete - 10-30cm

Question 6

LIDAR: Range Measurements

Answer 6

Range measurements: Measured as the time that it takes for the light pulse to move from the source (ie the instrument) to the reflecting object and back.

Question 7

LIDAR: Intensity Measurements

Answer 7

Intensity is the amount of energy that is returned to the instrument.

Question 8

LiDAR Constraints

Answer 8

• Do not measure to specific objects of interest

- Compensate by collecting lots of points (avg 10s of millions)

Question 9

Vegetation constraints

Answer 9

– Thickness and height from ground

– We normally do not measure tree height but canopy height

Question 10

Survey Accuracy Components

Answer 10

• Horizontal / vertical accuracy: x,y,z
• Relative Accuracy: where is it in relation to what is around it
• Absolute Accuracy: where is it in the world

Question 11

Products of LIDAR

Answer 11

• Surface Model
• Canopy Height Model
• Bare Earth Model