Caracterización espectral de Quillaja saponaria (Mol.)

Revista oficial de la Asociación Española de Teledetección[EN] This paper presents a spectral reflectance characterization of the specie Quillaja saponaria (Mol.), endemic tree of Chile and valued by society due to its provision of several ecosystem services that gives to society and also for its high concentration of saponins in cortex widely used in the pharmacological industry. For spectral characterization a foliar spectral signatures protocol was designed which included standardized instrumental and environmental parameters. The spectral response of different individuals was measured to evaluate the spectral behaviour and degree of variability within species in the visible and near infrared ranges (VNIR; 400-990 nm) with two hyperspectral sensors (ASD HH and camera PDF-65-V10E). The resulting spectral signatures obtained with ASD HH showed a variation less than 5% of reflectance in VNIR and lesser than that in the transition zone from red to near infrared (red-edge; 680-730 nm). Additionally, two distinctive spectral features were detected for the specie, the first is related to a fast increase of reflectance in bands 450-480 nm and the second, to a marked decrease in the 920-970 nm range associated with water absorption features. At branch level, these distinctive features are maintained but with a smaller magnitude of reflectance, which could indicate that they are useful characteristic spectral patterns that can eventually be used for monitoring the physical health state of the specie using remote sensing. On the other hand, we used a PDF-65 camera for study the plant vigour from different health states (healthy, ill, died) with spectral vegetation index. The Plant Senescence Reflectance Index detected stress on leaves, and Triangular Vegetation Index allows for a gradually characterization of every state. This work provides the first spectral reference for one of the most important sclerophyll species of Chile.[ES] En este trabajo se presenta una caracterización de la reflectancia espectral de Quillaja saponaria (Mol.), especie endémica de Chile y principalmente valorada por los servicios ecosistémicos que brinda a la sociedad así como su elevada concentración de saponinas en la corteza, utilizada como insumo en la industria farmacéutica. Para la caracterización espectral se diseñó un protocolo de adquisición de firmas espectrales foliares, controlando pará-metros instrumentales y ambientales. Se evaluó el comportamiento espectral y el grado de variabilidad de la especie en el rango del visible e infrarrojo cercano (VNIR; 400-990 nm) con dos sensores hiperespectrales (ASD HH y cámara PDF-65-V10E). Las firmas espectrales obtenidas con el ASD HH mostraron una variación inferior al 5% de reflectancia en el VNIR y en menor medida en la zona de transición del visible al infrarrojo cercano (red-edge; 680-730 nm). Además, se detectaron dos rasgos espectrales distintivos de la especie, el primero se relaciona con un incremento rápido de la reflectancia en los 450-480 nm y el segundo, un decrecimiento entre los 920-970 nm relacionado con las bandas de absorción de agua. De hecho, al medir la reflectancia de un conjunto de ramas apiladas, éstos rasgos perduran pero con una menor magnitud, indicando un patrón espectral característico y eventualmente utilizable en campañas de monitoreo del estado físico y sanitario de la especie mediante teledetección. Usando la cámara PDF-65 se estudió el vigor de las hojas bajo diferentes condiciones sanitarias (sana, enferma, muerta) a través de los índices espectrales de vegetación. Entre los resultados, el índice PSRI (Plant Senescence Reflectance Index) detecta sectores de bajo vigor fotosintético y el TVI (Triangular Vegetation Index) permite una caracterización gradual de cada condición. Este trabajo presenta la primera referencia espectral para una de las especies de bosque esclerófilo más importante de Chile.Este trabajo fue financiado por el proyecto Fondecyt 1140319 “Vegetation Knowledge-based Indicators for Urban Sustainable Planning” de CONICYT Chile. Los autores también agradecen a AGSEN y a SPECIM por contribuir con la imagen obtenida con la cámara hiperespectral PDF-65-V10E.Acuña, T.; Mattar, C.; Hernández, HJ. (2016). Spectral characterization of Quillaja saponaria (Mol.). Revista de Teledetección. (47):65-73. https://doi.org/10.4995/raet.2016.6488SWORD65734

Towards a metadata standard for field spectroscopy

This thesis identifies the core components for a field spectroscopy metadata standard to facilitate discoverability, interoperability, reliability, quality assurance and extended life cycles for datasets being exchanged in a variety of data sharing platforms. The research is divided into five parts: 1) an overview of the importance of field spectroscopy, metadata paradigms and standards, metadata quality and geospatial data archiving systems; 2) definition of a core metadataset critical for all field spectroscopy applications; 3) definition of an extended metadataset for specific applications; 4) methods and metrics for assessing metadata quality and completeness in spectral data archives; 5) recommendations for implementing a field spectroscopy metadata standard in data warehouses and ‘big data’ environments. Part 1 of the thesis is a review of the importance of field spectroscopy in remote sensing; metadata paradigms and standards; field spectroscopy metadata practices, metadata quality; and geospatial data archiving systems. The unique metadata requirements for field spectroscopy are discussed. Conventional definitions and metrics for measuring metadata quality are presented. Geospatial data archiving systems for data warehousing and intelligent information exchange are explained. Part 2 of the thesis presents a core metadataset for all field spectroscopy applications, derived from the results of an international expert panel survey. The survey respondents helped to identify a metadataset critical to all field spectroscopy campaigns, and for specific applications. These results form the foundation of a field spectroscopy metadata standard that is practical, flexible enough to suit the purpose for which the data is being collected, and/or has sufficient legacy potential for long-term sharing and interoperability with other datasets. Part 3 presents an extended metadataset for specific application areas within field spectroscopy. The key metadata is presented for three applications: tree crown, soil, and underwater coral reflectance measurements. The performance of existing metadata standards in complying with the field spectroscopy metadataset was measured. Results show they consistently fail to accommodate the needs of both field spectroscopy scientists in general as well as the three application areas. Part 4 presents criteria for measuring the quality and completeness of field spectroscopy metadata in a spectral archive. Existing methods for measuring quality and completeness of metadata were scrutinized against the special requirements of field spectroscopy datasets. Novel field spectroscopy metadata quality parameters were defined. Two spectral libraries were examined as case studies of operationalized metadata. The case studies revealed that publicly available datasets are underperforming on the quality and completeness measures. Part 5 presents recommendations for adoption and implementation of a field spectroscopy standard, both within the field spectroscopy community and within the wider scope of IT infrastructure for storing and sharing field spectroscopy metadata within data warehouses and big data environments. The recommendations are divided into two main sections: community adoption of the standard, and integration of standardized metadatasets into data warehouses and big data platforms. This thesis has identified the core components of a metadata standard for field spectroscopy. The metadata standard serves overall to increase the discoverability, reliability, quality, and life cycle of field spectroscopy metadatasets for wide-scale data exchange

Critical Metadata for Spectroscopy Field Campaigns

A field spectroscopy metadata standard is defined as those data elements that explicitly document the spectroscopy dataset and field protocols, sampling strategies, instrument properties and environmental and logistical variables. Standards for field spectroscopy metadata affect the quality, completeness, reliability, and usability of datasets created in situ. Currently there is no standardized methodology for documentation of in situ spectroscopy data or metadata. This paper presents results of an international experiment comprising a web-based survey and expert panel evaluation that investigated critical metadata in field spectroscopy. The survey participants were a diverse group of scientists experienced in gathering spectroscopy data across a wide range of disciplines. Overall, respondents were in agreement about a core metadataset for generic campaign metadata, allowing for a prioritization of critical metadata elements to be proposed including those relating to viewing geometry, location, general target and sampling properties, illumination, instrument properties, reference standards, calibration, hyperspectral signal properties, atmospheric conditions, and general project details. Consensus was greatest among individual expert groups in specific application domains. The results allow the identification of a core set of metadata fields that enforce long term data storage and serve as a foundation for a metadata standard. This paper is part one in a series about the core elements of a robust and flexible field spectroscopy metadata standard

Critical Metadata for Spectroscopy Field Campaigns

A field spectroscopy metadata standard is defined as those data elements that explicitly document the spectroscopy dataset and field protocols, sampling strategies, instrument properties and environmental and logistical variables. Standards for field spectroscopy metadata affect the quality, completeness, reliability, and usability of datasets created in situ. Currently there is no standardized methodology for documentation of in situ spectroscopy data or metadata. This paper presents results of an international experiment comprising a web-based survey and expert panel evaluation that investigated critical metadata in field spectroscopy. The survey participants were a diverse group of scientists experienced in gathering spectroscopy data across a wide range of disciplines. Overall, respondents were in agreement about a core metadataset for generic campaign metadata, allowing for a prioritization of critical metadata elements to be proposed including those relating to viewing geometry, location, general target and sampling properties, illumination, instrument properties, reference standards, calibration, hyperspectral signal properties, atmospheric conditions, and general project details. Consensus was greatest among individual expert groups in specific application domains. The results allow the identification of a core set of metadata fields that enforce long term data storage and serve as a foundation for a metadata standard. This paper is part one in a series about the core elements of a robust and flexible field spectroscopy metadata standard