Proceedings of the Symposium on Global and Environmental Monitoring: Proceedings of the Symposium on Global and Environmental Monitoring

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Persistent identifier:: 856665355

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts ; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856665355

Language:: English

Document type:: Multivolume work

Volume

Persistent identifier:: 856669164

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Scope:: XIV, 912 Seiten

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856669164

Illustration:: Illustrationen, Diagramme, Karten

Signature of the source:: ZS 312(28,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [THP-1 HIGH SPECTRAL RESOLUTION MEASUREMENT]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: The Ramifications of Sampling Methods for Imaging Spectrometers. J. Douglas Dunlop & John R. Miller

Document type:: Multivolume work

Structure type:: Chapter

571 The Ramifications of Sampling Methods for Imaging Spectrometers J. Douglas Dunlop 1 & John R. Miller 2 1. Earth Observations Laboratory, Institute for Space and Terrestrial Science Department of Geography, University of Waterloo Waterloo, Ontario, Canada, N2L 3G1 2. Department of Physics, York University Earth Observations Laboratory, Institute for Space and Terrestrial Science 4700 Keele Street, North York, Ontario, Canada, M3J 1P3 ABSTRACT Imaging spectrometers are capable of generating data at prodigious rates which can exceed the bandwidth of either the recording device or the transmission channel. This is a direct result of the spectrometer's potential for collecting high resolution both spectrally and spatially, simultaneously. Some form of sampling is commonly employed to reduce the volume of data, but this can have profound effects on the information content of the resulting signal. This paper will discuss the ramifications of some of the methods of sampling typically used on spectrometer data, vis-à-vis the loss of information. It will also consider new methods of sampling which have the potential of preserving more of the generic information content of the data, independent of any specific application. Key Words: Fourier, imaging, spectrometers, sampling. INTRODUCTION The decade of the environment is upon us. To identify pollu tants and to monitor their effects it will become increasingly important to use sophisticated remote sensors. With its ability to measure the spectrum in contiguous bands for each pixel, the imaging spectrometer promises to become the preeminent environmental sensor of the 1990's. Before the end of this decade spacebome imaging spectrometers will become opera tional and the number of spectral bands that are available to the satellite data user will increase by over an order of magnitude from what is currently available. The wealth of data produced by an imaging spectrometer provides both an opportunity and a challenge. The opportunity is to more accurately monitor terrestrial processes by remote sensing than has previously been possible using multispectral scanners. The challenge is to effectively cope with the prodigious volume of data so that we might tap its wealth of information. For example the NASA imaging spectrometer HIRIS due for launch in 1996 is capable of generating 500 Mbits/s of data. Currently it is not technologically practical to continuously digitize, transmit and record at 500 Mbit/s data rates. Colvocoresses (1977) and Schowengerdt (1980) both suggested that perhaps a mixture of critically placed low spatial resolution narrow spectral bands and a single high spatial resolution band may be the optimal way to reduce the data rates with minimal information loss. The CASI instrument implements this strategy in what is called the track recovery channel (Babey & Anger, 1989). More commonly, imaging spectrometers (both CASI and FLI) utilize modes of operation which operate with either high spectral resolution or high spatial resolution, but not both simultaneously (Buxton, 1988). Each of the above represents a different sampling strategy, but other strategies are possible and may turn out to be more effective. What artifacts are introduced by the sampling process? This paper attempts to shed light on the ramifications of the various sampling procedures so as to provide insight that may allow improved analysis. Finally, an alternate method of sampling is suggested that might be more appro priate for imaging spectrometers due to the strongly correlated nature of the signals they produce. BACKGROUND The list of known and planned spacebome imaging spectrom eters include HIRIS, HRIS, MODIS, and MERIS. Already in use as airborne systems are AVIRIS, ROSIS, AIS, FLI and CASI with the earliest flights dating back to 1983. Imaging spectrometers have high resolution in all domains; high spatial resolution, high spectral resolution and high radiometric resolution. The problem of how to effectively filter and reduce the volume of data and yet to retain the desired information has been considered in the context of multispectral imagery for many years. Image Sharpening A number of researchers have considered the problem of how to use information from a high spatial resolution band to sharpen the edges in other lower resolution bands. It was first suggested by Colvocoresses (1977) and first implemented when Schowengerdt (1980) presented his technique for restoring the high spatial frequency information to Landsat MSS imagery. Roller and Cox (1980) studied the possibility of improving classification accuracies and the interpretability of Landsat Multispectral Scanner (MSS) imagery by increasing its spatial resolution using Return Beam Vidicon (RBV) imagery. Hallada and Cox (1983) compared the methods of Schowengerdt with those of Roller and Cox using data from an airborne Daedalus 1260 multispectral line scanner. Hallada and Cox note that the combination of mixed spatial and spectral resolutions is very adaptable to the concept of imaging spectrometers. They state "On-board data compression would be a simple matter of integrating the signals across detectors in the spatial and/or spectral domains". Simard (1982) was first to propose that the SPOT 20 m multi spectral data could be sharpened by using the 10 m panchromatic band to modulate the brightness. Cliche et al. (1985) describe algorithms for integrating the SPOT panchro matic band with the multispectral bands to improve image sharpness to yield results resembling colour infrared photography. Tom and Carlotto presented a Least Mean Squares (LMS) approach to edge sharpening (Tom et al., 1984). It relies on the fact "that at sufficiently small resolution multispectral bands are strongly correlated", so if the digital levels of the any two bands are plotted against each other in a scatterplot then all the data will fall approximately along a straight line Any particular spectral band will generally not be globally correlated with the reference band (or bands), so the regres sions are performed adaptively within a sliding window which moves across the image.

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