1. INTRODUCTION
Airborne laser swath mapping (ALSM), often referred to as light detection and ranging (LiDAR), enables sub-meter spatial sampling of topography. An ALSM system pulses a near-infrared laser from an airborne platform to the ground several thousand times per second. By precisely determining the position and attitude of the aircraft as well as the angle at which each laser pulse leaves the aircraft, the direction of the laser pulse toward the ground can be accurately calculated. Combining this information with the recorded return time of the reflected pulse allows for a three-dimensional point sampling of the ground and landcover [1]. From the resulting ALSM point data, digital images are created in which the pixel value corresponds to the mean topographic elevation of the points within that pixel. These images often exhibit rms elevation errors of less than 10cm over minimally-vegetated surfaces, such as beaches. For most ALSM systems, the points also have associated intensity values, which can be similarly interpolated into an intensity image. To date, the intensity values have rarely been utilized by earth scientists, largely because they are only recorded as relative values. Thus, they are unitless and do not represent absolute surface radiance.