week 7

Question 1

what are types of laser scanning

Answer 1

• terrestrial laser scanning (TLS)
• mobile laser scanning
• airborne laser scanning and UAV-based laser scanning which are combined topographic and bathymetric laser scanning

Question 2

describe terrestrial laser scanning (TLS)

Answer 2

• provides detailed and incredibly accurate 3D data
• rapid and efficient methodology
• applications are wide-ranging in the “real world” and include:
• mapping of topography
• mining surveys
• monitoring - such as coastal retreat, possible landslips
• as-built surveying
• architecture surveys
• archaeology surveys
• civil engineering projects
• city models

Question 3

describe mobile laser scanning

Answer 3

• mobile laser scanning involves the acquisition of terrestrial data from moving platforms (e.g., boars, road and off-road vehicles)
• 2D and 3D scanning
• applications include:
• open pit mine surveys
• GID mapping and asset management
• transportation infrastructure mapping
• road surface measurements
• city modelling
• rail track mapping and clearance surveying

Question 4

describe airborne laser scanning

Answer 4

• used to capture 3D data of large areas
• rapid, extremely accurate and efficient
• compact, lightweight and cost effective
• airborne laser scanners use state-of-the-art laser and signal processing technology - comprise airborne mapping systems, cameras, high-end IMU/GNSS systems
• survey area could include:
• wide area mapping - capturing geomorphological and geological landscapes
• agricultural sites
• forestry sites (useful to monitor wildfires?)
• defence sites
• urban areas
• industrial areas

Question 5

describe UAV-based laser scanning

Answer 5

• high-end. unmanned (drone) airborne platforms
• allow for data acquisition from dangerous and hard-to-reach areas
• high cost to benefit ratio for various applications, including:
• wide area mapping - capturing geomorphological and geological landscapes
• flood zone mapping
• mapping of challenging topography
• mining surveys
• agriculture
• forestry
• defence

Question 6

what is combined topographic and bathymetric laser scanning

Answer 6

• Combination of airborne and UAV-based laser scanners sensors and systems
• Applications, including:
• Coastline and shallow water mapping
• Base data acquisition for floor prevention
• Measurement of aggradation zones
• Mapping of rivers and lakes
• Repeated surveys (monitoring) of water reservoirs
• Hydraulic engineering surveys
• Hydro-archaeology surveys

Question 7

what are IMUs

Answer 7

• Inertial Measurement Unit (IMU) – an advanced electronic device that is able to measure and report an object’s acceleration, angular rate, and orientation.
• IMUs consist of accelerometers, gyroscopes, and often magnetometers, which collectively provide crucial data for navigation, control systems, and stabilization

Question 8

GNSS vs GPS

Answer 8

GPS – Global Positioning System
GNSS (Global Navigation Satellite System) – encompasses multiple global navigation systems, inc. GPS, GLONASS, Galileo, BeiDou, etc. GNSS provides greater coverage and improved accuracy.

Question 9

describe the process of terrestrial laser scanning (TLS)

Answer 9

• HDS Surveying and LiDAR use lasers to measure and capture environments in 3D
• A laser is fired out and for every surface that the laser hits a point in space is recorded (xyz) in combination with DGPS equipment
• At the same time the scanner will record the reflectivity of the surface giving an intensity value in order to provide colour and an rgb value to each point
• Most scanners also have built in cameras that take a sequence of photos that can be draped over the points in space in a 3D model
• Points are captured at speeds of up to 1 million points of data per second creating a very dense point cloud of data.
• All laser scanner work via line of site and so a typical survey will include multiple scans taken from different vantage points in order to ensure a complete data set