Exploration of a Polarized Surface Bidirectional Reflectance Model Using the Ground-Based Multiangle Spectropolarimetric Imager

Accurate characterization of surface reflection is essential for retrieval of aerosols using downward-looking remote sensors. In this paper, observations from the Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI) are used to evaluate a surface polarized bidirectional reflectance distribution function (PBRDF) model. GroundMSPI is an eight-band spectropolarimetric camera mounted on a rotating gimbal to acquire pushbroom imagery of outdoor landscapes. The camera uses a very accurate photoelastic-modulator-based polarimetric imaging technique to acquire Stokes vector measurements in three of the instrument's bands (470, 660, and 865 nm). A description of the instrument is presented, and observations of selected targets within a scene acquired on 6 January 2010 are analyzed. Data collected during the course of the day as the Sun moved across the sky provided a range of illumination geometries that facilitated evaluation of the surface model, which is comprised of a volumetric reflection term represented by the modified Rahman-Pinty-Verstraete function plus a specular reflection term generated by a randomly oriented array of Fresnel-reflecting microfacets. While the model is fairly successful in predicting the polarized reflection from two grass targets in the scene, it does a poorer job for two manmade targets (a parking lot and a truck roof), possibly due to their greater degree of geometric organization. Several empirical adjustments to the model are explored and lead to improved fits to the data. For all targets, the data support the notion of spectral invariance in the angular shape of the unpolarized and polarized surface reflection. As noted by others, this behavior provides valuable constraints on the aerosol retrieval problem, and highlights the importance of multiangle observations.NASAJPLCenter for Space Researc

Development and Evaluation of "Where Are We?" Map-Skills Software and Curriculum

The "Where are We?" software and lessons are designed to help children in grades two through four learn to "translate" between the visually-perceived world that they sense around them, and the schematic representation of that landscape on a map. Field-based tests were developed to examine students' ability to absorb information in the real world and to transfer it onto a map and, conversely, the ability to absorb information from a map and transfer it into an action in the real world. Formative evaluation of a prototype version of "Where are We?" resulted in the following improvements in the instructional materials: more and prompter feedback for students, additional assessment tools for teachers, development of lessons to model successful map-using strategies, development of lessons to overcome common misconceptions, and replacement of text-based instructions with a voiceover demo. Educational levels: Graduate or professional