Evaluation of potential sites for hyperspectral data validation in Argentinean Pampas

BARRAZA, V.; COVI, M.; GRINGS, F.; GASSMAN, M. I.; PIEGARI, E.; DOGLIOTTI, A.I.

Frascati

Encuentro; Land Product Validation and Evolution (LPEV); 2018

In order to produceresearch-quality data from existing and future satellite observing systems, itis essential to perform extensive validation campaigns or to set up test sitesfor validation of radiometric variables. This is necessary to: (1) characterizesurface biophysical dynamics to develop appropriate retrieval algorithms and(2) for quality control of geophysical data derived from remote sensing data.Moreover, in the context of HYPERNETS project, which is going to develop a newlow cost hyperspectral radiometer (and associated pointing system and embeddedcalibration device for automated measurement of water and land bidirectionalreflectance), the availability of robust and well characterized fieldvalidation sites is critical. In particular, the availability of ancillaryinformation to contextualize radiometric measurements. In order to select atest site for satellite validation different characteristics should be takeninto account, like its radiometric properties, ecological relevance,accessibility, the existence of previous knowledge and/or timely ancillaryinformation. In the present study two possible sites are characterized in termsof their temporal and spatial variability of different optical properties basedon 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; EstaciónExperimental Agraria Balcarce - INTA), Buenos Aires (37° 45´ S; 58 °18 ´O)province (Argentina). Soybean crop is one of the most important crops inArgentine agriculture (more than 12 106 hectares cultivated). Afield campaign with several in situ measurements were conducted in this siteduring 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 themost important species that dominates coastal tidal marshes in Samborombon Bay,Mar Chiquita Coastal Lagoon. Coastal habitats provide ecosystem servicesessential to people and the environment. A field campaign with several in situmeasurements (and eddy covariance experiments) were conducted in this siteduring the 2017/2018. Both sites presentedinteresting characteristics to be selected as validation sites forhyperspectral data in the context of HYPERNETS. In Mar Chiquita site, dominatedby herbaceous natural vegetation, EVI (MODIS) presents more spatialheterogeneity and a strong seasonality, characteristic of natural vegetation.Moreover, as 2017, this is a heavily instrumented site, in which a lot ofancillary information is already available to contextualize radiometricmeasurements. Moreover, wetlands are very sensitive to environmental forcings,which could change the balance of energy and matter and which could be potentiallydetected using hyperspectral data. In turn, Balcarce sitepresents a typical soybean site, characterized by a fixed two crop cycle (croptype may change among years) which is both more spatial and temporallyhomogeneous. However, changes in phenological patterns due to environmentalforcings (dries) in this site should have more spatially homogeneous patterns.More importantly, it was shown that these changes produce subtle changes in theradiometric signature, which could be better monitored using hyperspectraldata.