Image Processing

Orthorectification combines UAV flight imagery into a single image with high accuracy of the geolocation and reflectance for each pixel and each spectral band scientifically calibrated. AggieAir employs orthorectification software that uses photogrammetry and pattern recognition technology to ensure the highest possible quality data products.

Proper design and installation of a ground control network is critical in ensuring the accuracy in orthorectification. AggieAir reports geopositional accuracy measures of its imagery for every mission and has published comparative research on orthorectification accuracy as measured against independently acquired lidar data.

Radiometric calibration translates digital/integer pixel values for each wavelength in each image into meaningful scientific data which measures the energy reflected in each spectral band from photographed surfaces. Calibration allows researchers to quantify more than simple measures of areas and lengths. AggieAir researchers have developed and published protocols to correct for vignetting and accurately calculate reflectance using a wide array of data including measurement of incident light and environmental attenuation factors in the air column. AggieAir continues to refine and advance radiometric calibration research to address challenges presented by greater flight distances and duration over increasingly challenging geography.

References:

• Use of high-resolution multispectral imagery acquired with an autonomous unmanned aerial vehicle to quantify the spread of an invasive wetlands species
• Reflectance Data Processing of High Resolution Multispectral Data Acquired with an Autonomous Unmanned Aerial Vehicle: AggieAir^TM
• Retrieval of Spectral Reflectance of High Resolution Multispectral Imagery Acquired with an Autonomous Unmanned Aerial Vehicle, AggieAir^TM

A frequent challenge of UAV remote sensing is acquiring consistent high-quality estimations of surface temperatures using microbolometer infrared cameras, which are highly sensitive to atmospheric attenuation in infrared ranges. AggieAir researchers have developed scientifically based calibration software that relies on field protocols and on-board environmental sensors to compensate for these calibration challenges and create consistent, high-quality thermal data.

References:

• Thermal remote sensing with an autonomous unmanned aerial remote sensing platform for surface stream temperatures
• Calibrating High-resolution Thermal Imagery from a Small Unmanned Aerial System: AggieAir
• The remote sensing data from your UAV probably isn’t scientific, but it should be!
• Vicarious Calibration of sUAS Microbolometer Temperature Imagery for Estimation of Radiometric Land Surface Temperature