LiDAR

Question 1

What is photogrammetry?

Answer 1

Third dimensonal extraction from photographs by taking overlapping photographs of a feature and converting them to 3D models

Question 2

What is one of the biggest problems of image capture?

Answer 2

If you can not see the object in the photo, we can not see it at all

Question 3

What is point cloud generation?

Answer 3

Datasets that represent objects with x, y, and z geometric oordinates of a single point on a sampled surface

AIrborne LIDAR platforms can produce a dense array of reflection points

Question 4

How does LiDAR work?

Answer 4

A laser pulse is emitted and the distance is measured based on the time it takes for it to be sent out and reflected back from target

Travels at speed of light = can be converted to distance D = C(speed of light) x T / 2

Question 5

LiDAR is great for

Answer 5

Terrain mapping

Question 6

What does Airborne LiDAR consist of?

Answer 6

Computer to record
High frequency laser scanner (derives the x, y, z coordinates for each pulse returned)
GPS
IMU/INS

IMU / INS: angular orientation of the sensor with respect to the ground
COMMON WAVELENGTH IS NIR

Question 7

By 2000, commercial systems became…

Answer 7

Capable of measuring multiple returns per pulse (3-5)

Question 8

What is an issue of LAS file format?

Answer 8

Interchange of 3D point cloud data into elevation data format can be very slow and the file size can be extremely large, requiring a special viewer

Question 9

What does LAS file format contain?

Answer 9

Generic data such as point numbers
Variable types of data such as metadata
Point data such as coordinates, intensity, etc

Question 10

What are some LiDAR applications?

Answer 10

High resolution DSM
High resolution DEM
Forestry (canopy height modelling)
3D City Modelling
Archaeology