Evaluation of potential sites for hyperspectral data validation in Argentinean Pampas

BARRAZA VERÓNICA; COVI MAURO; GRINGS FRANCISCO; GASSMANN MARÍA ISABEL; PIEGARI ESTEFANÍA; DOGLIOTI ANA

Frascati

Workshop; Workshop on Land Product Validation and Evolution (LPVE 2018) ESA/ESRIN; 2018

Europa Space Agency

In order to produce research-quality data from existing and future satellite observing systems, it is essential to perform extensive validation campaigns or to set up test sites for validation of radiometric variables. This is necessary to: (1) characterize surface biophysical dynamics to develop appropriate retrieval algorithms and (2) for quality control of geophysical data derivedfrom remote sensing data. Moreover, in the context of HYPERNETS project, which is going to develop a new low cost hyperspectral radiometer (and associated pointing system and embedded calibration device for automated measurement of water and land bidirectional reflectance), the availability of robust and well characterized field validation sites is critical. In particular, the availability of ancillary information to contextualize radiometric measurements.In order to select a test site for satellite validation different characteristics should be taken into account, like its radiometric properties, ecological relevance, accessibility, the existence of previous knowledge and/or timely ancillary information. In the present study two possible sites are characterized in terms of their temporal and spatial variability of different optical properties based on information from existing is situ and satellite-based sensors like MODIS.The Balcarce site (soybean crop site) is located in the area of Balcarce (UIB; Estación Experimental Agraria Balcarce - INTA), Buenos Aires (37° 45´ S; 58 °18 ´O) province (Argentina). Soybean crop is one of the most important crops in Argentine agriculture (more than 12 10 6 hectares cultivated). A field campaign with several in situ measurements were conducted in this site during the 2012/2013 summer season. The other site is located in Mar Chiquita, Buenos Aires (37° 33´ S; 57 °17 ´O) province (Argentina). In this site the vegetation is dominated by Spartina densiflora, which is one of the most important species that dominates coastal tidal marshes in Samborombon Bay, Mar Chiquita Coastal Lagoon. Coastal habitats provide ecosystem services essential to people and the environment. A field campaign with several in situ measurements (and eddy covariance experiments) were conducted in this site during the 2017/2018.Both sites presented interesting characteristics to be selected as validation sites for hyperspectral data in the context of HYPERNETS. In Mar Chiquita site, dominated by herbaceous natural vegetation, EVI (MODIS) presents more spatial heterogeneity and a strong seasonality, characteristic of natural vegetation. Moreover, as 2017, this is a heavily instrumented site, in which a lot of ancillary information is already available to contextualize radiometric measurements. Moreover, wetlands are very sensitive to environmental forcings,which could change the balance of energy and matter and which could be potentially detected using hyperspectral data.In turn, Balcarce site presents a typical soybean site, characterized by a fixed two crop cycle (crop type may change among years) which is both more spatial and temporally homogeneous. However, changes in phenological patterns due to environmental forcings (dries) in this site should have more spatially homogeneous patterns. More importantly, it was shown that these changes produce subtle changes in the radiometric signature, which could be better monitoredusing hyperspectral data.