Chris Bellman

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.

A Shape-Based Vector Watermark for Digital Mapping

Digital vector maps are an expensive commodity. Like any digital data, they are also very easy to copy. Piracy (or unauthorised reselling) of maps will become increasingly common in the future. This project looks at embedding a hidden message or watermark in a digital map so that its original authorship can be ascertained. This information enables a 3rd party to verify a sellers rights to the map and aid in the resolution of copyright disputes. Some other vector watermarking schemes, look at vector maps as a cloud of coordinates, to be perturbed in some way that is independent of actual usage. These papers generally do not discuss how large a subset of the map is needed to reliably retain the watermark. Instead, we concentrate on watermarking map feature lines, so that feature extraction from a watermarked vector map may not necessarily compromise watermark integrity.

Assessing Field Spectroscopy Metadata Quality

This paper presents the proposed criteria for measuring the quality and completeness of field spectroscopy metadata in a spectral archive. Definitions for metadata quality and completeness for field spectroscopy datasets are introduced. Unique methods for measuring quality and completeness of metadata to meet the requirements of field spectroscopy datasets are presented. Field spectroscopy metadata quality can be defined in terms of (but is not limited to) logical consistency, lineage, semantic and syntactic error rates, compliance with a quality standard, quality assurance by a recognized authority, and reputational authority of the data owners/data creators. Two spectral libraries are examined as case studies of operationalized metadata policies, and the degree to which they are aligned with the needs of field spectroscopy scientists. The case studies reveal that the metadata in publicly available spectral datasets are underperforming on the quality and completeness measures. This paper is part two in a series examining the issues central to a metadata standard for field spectroscopy datasets.

The impact of size variations in the ground instantaneous field of view of pixels on MODIS BRDF modelling

Abstract Bidirectional reflectance distribution functions (BRDF) seek to represent surface reflectance anisotropy resulting from surface physical structure and changes in a satellite sensor’s view and solar illumination angles. NASA’s MODerate resolution imaging spectroradiometer (MODIS) is a wide field of view sensor that generates observations over a large range of view angles. Based on MODIS observations, a BRDF product and several sub-products have been developed by MODIS science teams, i.e. the MCD43 product suite. Variations in pixels’ ground instantaneous field of view (GIFOV), i.e. the size of a pixel’s footprint on the ground, is a well known effect associated with wide field of view sensors such as MODIS, but is not specifically considered in the MODIS BRDF algorithm nor has research been undertaken into its effects on MODIS BRDF modelling. This paper introduces two metrics to examine the relationship between reflectance variations associated with changes in MODIS pixels’ GIFOV and the MODIS BRDF (MCD43) product. These metrics are applied to four different study areas and epochs across the Australian continent. The two metrics are shown to be well correlated (mean correlation coefficient of 0.81 for the four study areas); suggesting that variations in pixels’ GIFOV are a consistent, non-random source of variance in MODIS BRDF modelling. The results contained in this paper suggest that all downstream products which include MODIS BRDF processing in their derivation and results directly based on MODIS BRDF processing may need to be reassessed.

Approaches to establishing a metadata standard for field spectroscopy datasets

There is an urgent need within the international remote sensing community to establish a metadata standard for field spectroscopy that ensures high quality, interoperable metadata sets that can be archived and shared efficiently within Earth observation data sharing systems. Careful examination of all stages of metadata collection and analysis can inform a robust standard that is applicable to a range of field campaigns. This paper presents approaches towards a standard that encompasses in situ metadata collection and initiatives towards sharing metadata within intelligent archiving systems.

Towards an Interoperable Field Spectroscopy Metadata Standard with Extended Support for Marine Specific Applications

This paper presents an approach to developing robust metadata standards for specific applications that serves to ensure a high level of reliability and interoperability for a spectroscopy dataset. The challenges of designing a metadata standard that meets the unique requirements of specific user communities are examined, including in situ measurement of reflectance underwater, using coral as a case in point. Metadata schema mappings from seven existing metadata standards demonstrate that they consistently fail to meet the needs of field spectroscopy scientists for general and specific applications (μ = 22%, σ = 32% conformance with the core metadata requirements and μ = 19%, σ = 18% for the special case of a benthic (e.g., coral) reflectance metadataset). Issues such as field measurement methods, instrument calibration, and data representativeness for marine field spectroscopy campaigns are investigated within the context of submerged benthic measurements. The implication of semantics and syntax for a robust and flexible metadata standard are also considered. A hybrid standard that serves as a “best of breed” incorporating useful modules and parameters within the standards is proposed. This paper is Part 3 in a series of papers in this journal, examining the issues central to a metadata standard for field spectroscopy datasets. The results presented in this paper are an important step towards field spectroscopy metadata standards that address the specific needs of field spectroscopy data stakeholders while facilitating dataset documentation, quality assurance, discoverability and data exchange within large-scale information sharing platforms.