NLAS: Improving the Accessibility and Utility of Lidar Waveform Data in the Earth Sciences Abstract

abstract

  • Lidar (Light detection and ranging) is finding an increasing number of applications in the Earth sciences. Upward trends in the number of sources and the volume and complexity of lidar data present significant challenges for existing Earth science data systems tasked with serving these data. Moreover, scientists not accustomed to working with lidar often encounter barriers in discovering, accessing, decoding, analyzing and interpreting the data. Conversely, the groups acquiring lidar data struggle to deliver data products in standardized and self-describing formats that allow the various applications communities to fully utilize their data. A collaborative project funded by the NASA ROSES ACCESS program is developing a system that provides access to and services on existing lidar data archives. Working with data from satellite, low- and high-altitude airborne and terrestrial lidar platforms, we are attempting to harmonize the terminology, quality indicators, structure and encodings of these data to improve their accessibility and utility. The Web service-based systems created by this project, called NLAS (NASA Lidar Access System), provide federated access to lidar archives hosted at the National Snow and Ice Data Center DAAC, Goddard Space Flight Center LVIS Data Center, UNAVCO, and the OpenTopography Facility at the San Diego Supercomputing Center (SDSC). NLAS systems will provide access to satellite laser altimetry data from ICESat and high altitude airborne laser scanning data from LVIS, as well as low altitude airborne LiDAR and terrestrial laser scanning data hosted at OpenTopography and UNAVCO. NLAS uses instances of RAMADDA, an open-source, web-based content repository and publishing platform, to service search, subsetting, format conversion, and data transfer requests. Automated metadata extraction and generation by RAMADDA, and the generation of reader code based on a data dictionary, eases data ingest. The OpenTopography portal acts as a client to the NLAS services and provides integrated access to the GSFC and NSIDC-hosted datasets along with OpenTopography hosted data. In addition to providing access to LiDAR point data OpenTopography provides on-demand generation of user-specified derived topographic data products. Data distilled from the 15 standard ICESat products will be made available through NLAS. The LVIS waveform vector is a unique method for storing lidar waveforms that allows end-users to perform their own waveform analysis at full accuracy. An expanded version of this LVIS data product will be available through NLAS. NLAS is also developing a unified lidar data content and encoding convention to enable straightforward and unambiguous interpretation of waveform data (single and multiple waveforms per footprint) with the aim of spurring the broader adoption of both space and airborne lidar waveform data and increase opportunities for joint analysis of such data sets.

authors

publication date

  • 2011

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