|Rango, Albert - Al|
|Peters, Debra - Deb|
Submitted to: Remote Sensing of Environment
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/2/2006
Publication Date: 8/23/2006
Citation: Chopping, M., Su, L., Laliberte, A., Rango, A., Peters, D.P.C., Kollikkathara, N. 2006. Mapping shrub abundance in desert grasslands using geometric-optical modeling and multi-angle remote sensing with CHRIS/proba. Remote Sensing of Environment 104:62-73. Interpretive Summary: The Jornada Experimental Range (JER) is one of 22 core sites chosen worldwide for the Compact High Resolution Imaging Spectrometer (CHRIS) on the European Space Agency PRoject for On-Board Autonomy (PROBA) satellite. Because these data are new and limited in number, we do not know if they will be useful for arid land shrub mapping. We used the CHRIS/PROBA 631nm multi-angle reflectance data along with a geometric-optical model and some canopy assumptions to evaluate the data. The results showed that the observed directional signal in the CHRIS geometrics can be explained in terms of soil understory-background response and woody shrub cover. The fractional woody shrub cover can be obtained using the multiangle data and modeling techniques. The techniques developed here at JER might well be used operationally over large desert grassland areas. Scientific agencies may be able to use multiangle data to assess woody shrub cover in remote and sparsely settled regions.
Technical Abstract: This work examines the application of a geometric-optical canopy reflectance model to provide measures of woody shrub abundance in desert grasslands at the landscape scale. The approach is through inversion of the non-linear simple geometric model (SGM) against 631 nm multi-angle reflectance data from the Compact High Resolution Imaging Spectrometer (CHRIS) flown on the European Space Agency's Project for On-Board Autonomy (Proba) satellite. Separation of background and upper canopy contributions was effected by a linear scaling of the parameters of the Walthall bidirectional reflectance distribution function model with the weights of a kernel-driven model. The relationship was calibrated against a small number of sample locations with highly contrasting background/upper canopy configurations, before application over an area of about 25 square kilometers. The results show that with some assumptions, the multi-angle remote sensing signal from CHRIS/Proba can be explained in terms of a combined soil-understory background response and woody shrub cover and exploited to map this important structural attribute of desert grasslands.