Monitoring detailed land surface changes using an airbornemultispectral digital camera system

Airborne multispectral digital camera systems provide the potential for flexible and inexpensive monitoring of land surface changes at high spatial resolutions. The goal of this study was to characterize the radiometric properties and processing requirements of Airborne Data Acquisition and Registration (ADAR) System 5500 data in the context of environmental monitoring applications. This airborne multispectral digital imaging system, manufactured and operated by Positive Systems Inc., consists of four digital cameras and an on-board digital capture system. Sensor lab tests of the digital cameras were conducted to determine spatial uniformity of image brightness, high frequency noise and signal-noise ratio (S/N), linearity of radiometric response, spectral response, and radiometric normalization and calibration. Submeter resolution ADAR 5500 data were acquired over constructed and natural coastal marshes, concurrent with ground-level radiometric and plant measurements, ADAR 5500 data were found to have high radiometric fidelity and were successfully normalized and calibrated using simple procedures and knowledge that the radiometric response is linear. Noise levels were low, and S/N was about 120 for lab test images and 90 for airborne images of the marsh complex. Vignetting effects were evident in lab images, which were inverted and low-pass filtered to generate a correction mask. Spatial and temporal differences of spectral reflectance between important marsh vegetation cover types represent “environmental signals” in the context of monitoring habitat restoration projects