Overview of Airborne Platforms and Sensors Flashcards
Limitations of quadrat research
- time intensive
- may not be representative
Limitations of satellites
- resolution
- atmosphere gets in the way
Uses of airborne remote sensing
- can help understand ‘sub pixel’ processes in courser resolution data (will have a higher resolution)
- Parameterise and / or validate models against
real-world data - Standalone or exploratory datasets
Applications of airborne remote sensing
- Climate research and carbon dynamics
- conservation and land management
- precision agriculture
- forestry
- Land surface dynamics
- Coastal and Marine systems
- Wildlife population studies
- Archaeology
- Mapping
- Civil Engineering and construction
- Infrastructure and network monitoring
- Resource Exploration
What are the two broad categories of airborne platforms
- Crewed Aircraft
- Uncrewed Aerial Systems
Pros of crewed aircraft
- high payload capacity
- Negligible risk of loss
- On-board decision making
- Intermediate spatial scales (quite large)
- On demand & flexible
- Not limited by line-of-sight
- Site access not required
Cons of crewed aircraft
- Installations require certification
- Finite weight, space, power, balance
- Airport within reasonable distance of site
- On small, unpressurised aircraft, sensor environment is challenging:
(T, P, humidity, Vibration, Contamination, Limited in-flight access)
UK(/EU) UAS classification
> 25kg Airworthiness and remote pilot licensing
requirements
<25kg Classified by weight and technical
equipment and rules on flying near civilization depend on pilot qualification and operator approvals
UAS pros
- Portability
- Repeatability
- Low cost – at small spatial scales
- Ultra-high resolution
- Accessibility
- Hover and point (multi-rotors)
- ‘Dull, Dirty and Dangerous’
UAS cons
- Very limited spatial coverage
- Inefficient for covering large areas
- Very limited payload
- Access to recharging
- No airworthiness standards – risk of component
failure - Inexperience, procedural & human errors lead to
accidents - And regulatory limitations…
UAS Regulatory Limitations UK (/EU)
- registration
- line of sight rule (400ft vertical)
- urban areas (qualification needed)
- airspace restrictions
- Subject to change
Two platform options for unmanned aircraft
Multi rotor and fixed wing
Multi rotor pros and cons
- Can operate virtually anywhere
- Slow or hovering flight:- Low level imaging- Extreme resolution and/or overlap- Long integration times
- Very limited endurance (e.g. ~15 min)
Fixed wing UA pros and cons
- Longer endurance
- Fewer moving parts
- Need more space
- Higher speed → lower resolution
- Same line of sight rules apply
7 criteria for selecting a UAS platform
- Platform Payload vs Sensor Specs (don’t forget mounting / gimbals etc.)
- Endurance – keep in mind the effect of sensor weight
- Area to be covered
- Ability to hover / fly slowly
- Operating area characteristics
- Gimbal support & sensor triggering / logging
- Development time / resources available
Passive sensors
- RGB cameras
- Multispectral cameras
- Hyperspectral imaging systems
- Thermal cameras
Active sensors
- LiDAR
- Radar
What do RGB cameras measure
- Each pixel on the sensor element contains 3 detectors (one each for red, green and blue channels)
Multispectral cameras
Typically multiple co-aligned and synchronised monochromatic sensors.
When combined, each pixel contains information on a number (~4-10) discreet, separate bands (an image per band)
Hyperspectral
- Each Pixel contains response value for 10’s
or 100’s of contiguous spectral bands
What is a hyperspectral data cube?
look this up
Thermal cameras, what do the pixels show?
Each pixel holds one value covering a broad
band in the IR (i.e. ‘monochromatic’)
How do thermal cameras help in farming?
They help distribute limited water resources in an educated way
Main limitation of thermal imaging
resolution lost
Lidar main pro
you can remove layers
Typical wavelengths for Topographic LiDAR
NIR (e.g. 905nm, 1550 nm)
Typical wavelengths for Bathymetric LiDAR
Green (~ 532 nm)
Supporting measurements in airborne sensing
- Ground Control Points
- Pre / Post -flight spectral
calibration - In-flight spectral calibration targets
- Atmospheric optical
measurements
