Aerial Survey: Methods and Uses

• Aerial survey is a method of collecting imagery by using airborne platforms like airplanes, helicopters, UAVs, and balloons.
• It is distinguished from satellite imagery due to its better resolution, quality, and atmospheric conditions.

Aerial Survey Uses

• Archaeology
• Fishery surveys
• Geophysics
• Hydrocarbon exploration
• Land surveys
• Mining
• Mineral Exploration
• Monitoring wildlife and insect populations (aka aerial census or sampling)
• Monitoring vegetation
• Ground cover
• Reconnaissance
• Transportation projects alongside ground surveys

History of Aerial Surveys

• The use of aerial surveys to monitor large ungulates can be traced back to 1935
• The use of aircraft, particularly helicopters, has grown since the 1950s
• It is applied in enumerating many ungulate species
• Total counts have been applied to many species of African ungulates
• Several species such as impala, topi, sitatunga, eland, and waterbuck are found in Rwanda and have been studied via aerial survey

Terrain Considerations

• Aerial surveys approximate a total count in moderate relief open habitats like savanna' and coastal marshes
• Deciduous forest habitat on a herd of known size within an enclosure is also suitable
• Winter/dry season surveys and counting in early morning and late evening are best

Infra-red additions

• A recent addition to aerial survey techniques includes infra-red scanning devices.
• Croon used infrared scanning devices from an airplane to census deer in the George Reserve enclosure in Michigan
• Results showed 98 Deer located via this method against 101 with a drive census in good conditions, suggesting that infrared scanning yields better results over large areas.

Limitations of Infra-red

• Infra-red scanning cannot penetrate green leafy canopy
• Temperature variability of animals and the background is too high
• It is difficult to distinguish different species of animals
• It entails a high cost for the scanning device

Aerial Survey Sensors

• Sensors fixed to the aircraft with a line-of-sight to the target remotely sense
• Manned aircraft accomplish this through an aperture or external wing strut mount, while UAVs mount sensors inside
• Examples of sensors are the Vexcel UltraCam, Leica ADS100, WaldoAir XCAM, RIEGL LMS-Q780, and Trimble AX80
• Systems typically operated include Flight navigation software, GNSS, Gyro-stabilized mount, and Data storage

Aerial Survey Approaches

• Manned aerial survey
• Unmanned aerial survey

Manned Aerial Survey

• This can be done with a Cessna, Piper Super Cub, Christen Husky, Bellanca Scout, or helicopter
• It has its limitations

Manned Aerial Survey Limitations

• Detractors due failure to ensure assumptions are met
• It requires experienced observers with high costs
• There is poor performance caused by observer fatigue or bias
• There is difficulty in standardization of the methodology

Manned Aerial Survey Methods

• Helicopters are beneficial in surveying wildlife in rugged terrain
• As there are a few options available, standards depend on method used
• Differing circumstances may demand different choices within a survey

Manned Aerial Survey classifications:

• Complete census: Total counts involve an exhaustive search of an entire survey area
• Sample counts, referred to as SRF, involve taking samples of part of a population, then estimating the population size.

Sample Count Method Approaches

• Fixed sample methods
• Transect sample surveys
• Block sample surveys
• Variable sample methods
• Distance counts

Total Counts

• The goal is to count every animal in the designated area by visually searching and reducing animal movement effects
• Conducted by flying along very close flight lines, not necessarily straight, depending on terrain
• Not practical for large areas except when divided into smaller strata
• Typically used for special target species less effectively counted in SRF

Total Counts applications

• When there is a precision requirement for complete census
• When a stratum requires a high coverage within the overall design
• When an area is less than 100km2

Total Counts Advantages

• Problems of sampling are avoided, simplifying the surveyor's task.

Total Counts Shortcomings

• There’s a “dead” zone below the aircraft making it difficult to see animals
• Navigation has to be accurate to cover all ground
• Animals may be counted twice because of the close spacing of flight lines
• Resources may not be available or are too expensive

Total Counts Procedure

• Aircraft proceeds to start line of search area
• Crew then begins spotting target species
• When a sighting is made, the spotter announces details, and an FSO records position, direction, etc.
• The procedure includes returns for photography, updating forms, and crew involvement in tracking groups and areas counted
• Finally Data is downloaded, mapped, and checked for duplicates, followed by a total production for the survey region

Transect Sample Counts

• It relies on the assumption animals are distributed similarly in the sample strip

• If animals gather, very high counts appear in some transects and low or no counts in others

• It is carried out by flying at a fixed height above ground

• Observers count animals between rods to estimate densities within each stratum and combine for an overall estimate

Transect Appropriateness

• When resources are limited
• Required precision allows for lower sampling intensity
• It may be impractical for intensities exceeding 40%
• Coverage can be enhanced by carrying out multiple independent sample counts

Height for Transects

• Constant height should be maintained using a radar altimeter for primarily flat areas

Flight Procedure

• Crew boards, confirms equipment and status
• The Pilot takes off and flies to the transect area
• The FSO records takeoff time and announces session details
• Transects are flown while the FSO announces numbers that are recorded
• RSOs record animal observations through codes, group sizes, and any pictures taken

Postflight Procedure

• The aircraft is parked, and the ground coordinator ensures data is taken care of
• The GC provides forms and downloads data, checks forms, and maps flight paths
• The GC debriefs crew and makes plans

Block Sample Counts

• It is conducted by dividing the survey area into equal sized "blocks"
• A total count is carried out in each block

Block Count Applications

• It is necessary in mountainous areas because sampling units can be searched efficiently
• Wherever transect counts can occur, if radar altimeters are not available

Transects vs Block counts

• Transect counts have a higher precision so they are preferred to maximize cost-effectiveness

Key for Method Selection

• The key is the sampling effort to meet survey objectives in strata that are greater than 70%
• The range to be counted helps with selecting the method

Aerial Survey Standardizations

• The plan will depend on the survey objective, hypothesis, and question
• The limits of the survey area should be defined and stored digitally
• The survey area is divided into subunits based on known populations
• To maximize precision, the stratum boundaries are defined with similar densities for species.

Strata are:

• Each of uniform topography
• Each of homogeneous densities of animals
• Enough to contain 15 sampling units at the desired sampling intensity
• Boundaries defined digitally with identifying codes

Sampling units

• If a total census is not being taken, a representative sample will be selected.
• Sampling units can be transects or blocks

Transects

• Oriented with the ecological gradient
• Selected systematically
• Described by positions of start and endpoints for uploading to a GPS

Blocks

• Should be a rectangular quadrat not larger than 15 km2
• Should be selected systematically or randomly from a grid covering the entire stratum
• Stored electronically in suitable format to upload to a GPS

General Sampling Guidelines

• Each sampling unit has a number prefixed by the stratum code.
• Survey design should maximise precision within available resources

Aircraft

• Safety is crucial and the aircraft needs to be suitable
• Experienced pilots only
• Standard flying safety procedures should be followed
• Where possible, same type aircraft should be used

Transect vs Block Aircraft

• Cessna’s are typically used for transect sample counts
• Aircraft such as a Piper Super Cub can be used for Block Counts b/c they aren’t suited for Transect

Strips

• For transect counts, two markers on each side of the aircraft mark the edges of the strip

Navigation equipment

• Should include a map of the area and a GPS that uploads, downloads, and records position
• To maintain and record height the aircraft must be fitted with a radar Altimeter
• An intercom must be fitted for crew communication

Recording animal sightings

• Animal sightings can be recorded with a tape recorder

Photographic equipment

• Photos can be beneficial, but practicality may make them less useful
• The following must be considered to validate sightings: camera, location, visibility, distraction
• Not switching between camera and not must be calibrated

Crew

• Should have, at the least, a Pilot, recorder, left observer, and right observer. If a recorder is unavailable then each observer must observe both sides of the strip.

Qualifications

• The pilot should have at least a commercial license and 1000 hours of flight time
• The recorder should have experience with surveys, recordings, and decisions
• Observers should have adequate training and be able to determine species, create calibrations, and estimate numbers

Surveys/calibration

• Surveys must be carried out as the right time of the year and day such that visibility is high for observer

Transect Strips calibration

• Calibration is done by flying across numbered markers at 10m intervals
• Though left and right values are obtained, it is carried out for the pairs of observers
• Height is varied between 250 and 350 feet
• Standard error of mean calibrated strip should be less than 5%

Guidelines for surveys

• Surveys must cover the entire survey area within as short a time as possible.
• Transects and total counts should be flown at 100 mph or less.
• Transects are flown with GPS

Strat Height

• Ground height should stay at 300ft when flying transects and should record every 30 seconds
• On blocks and total counts, the crew adjust optimally while ensuring safetly

Counting

• The ratio of flight time to counting time should be minimized
• Records of searching, positioning, and commuting kept

Sightings

• Obsevers should focus on species of Inerest
• Sightings must be confirmed by references to the strip markers and the GPS

Fatigue Precautions

• Fatigue should be avoided and there should be time allocated for breaks

UAV

• A UAV is a remotely piloted aircraft system (RPAS)

Standard UAV Equipment

• Unmanned Aircraft System
• Ground control station
• Pilot
• Visual observer
• Launcher

Aircraft Weight

• Less than 55 lbs (25 kg)

Advantages of UAV/drone usage

• Drones offer a safe, low cost way to observe natural phenomena at high spatial-temporal resolution, and systematically. Making the drones a Wildlife Research and management trend

UAV design

• Many designs have been tested for stability: fixed- and rotor-wing aircraft are popular

• Experimental designs, with the hummingbird shape as an example, were also developed and introduced.

• When considering the target area and the topological features are contemplated, operation speed and flight path must be skillfully determined.

• The success of drones can be partially explained by their great flexibility to carry different sensors and devices. The scope of application determines the best combination of aerial platform and payload

• Widespread small fixed-wing and rotary-wing aircrafts are frequently used for video and still photography

• Consumer grade drones with lightweight cameras and multispectral sensors supply professional mapping solutions at a fraction of a cost

• Thermal vision cameras, hyperspectral sensors and LiDAR compact thermal vision cameras, hyperspectral sensors and LiDAR are equipped medium size drones for wildlife ecology, vegetation studies, and forestry purposes.

• Drones can incorporate diverse instruments to measure temperature, humidity, and air pollution

• Large aerial platforms can lift heavier payloads and represent an appropriate solution for integrating complex systems with the capacity to remotely assist sampling

• The design and size of any UAV has many RPAS's merits in wildlife detection and monitoring: safety, reasonable prices, manpower required and flexibility in use.

• The UAV can fly in areas not suitable for humans or dangerous

• An UAV costs less than a helicopter

UAV Applications

• Drones use is growing through many wildlife-related applications, including monitoring of birds, marine mammals, large terrestrial mammals, and reptiles; wildlife habitat assessment and modeling; and wildlife conflict management.

• Examples are: Agriculture, civil engineering, environmental studies, humaritarian efforts

• UAV applications inclued: Poaching and game surveys, wildlife surveys, border integrity, crowd control and monitoring, Search and rescue, traffic monitoring, etc…