ASD A100800, User Manual

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© 2007 ASD Inc. 35 TerraSpec® User Manual
Chapter 6 Field Measurements
Spectrometry is the quantitative measurement of reflectance, transmission, or
absorption. It involves the collection of accurate spectra and requires an
awareness of the influences of:
Accurate and repeatable material analysis or identification requires the
accurate and repeatable measurement of reflectance, transmission, or
absorption. It requires an awareness of the influences of:
• Sources of illumination.
• Instrument field-of-view.
• Sample viewing and illumination geometry.
• Instrument scanning time.
• Spatial and temporal variability of the sample characteristics.
Many of these parameters are controlled when using one of ASD’s standard
sampling interfaces (e.g., MugLite or Contact Probe).
Spectral measurements are desirable for many reasons.
• Spectra of target materials allows for more precise image analysis and
interpretation.
• Spectroscopy can perform feasibility studies to understand if and how a
process or material of interest can be detected using remote sensing.
• Field spectra can be used to make direct material identifications in the
field rather than collecting samples for later laboratory analysis.
The first step in the development of a field experiment is the definition of the
overall experimental design. Unfortunately, the formulation of an appropriate
experimental design is not always obvious.
Issues such as the timing of the data collection, spatial scale of the field
measurement, target viewing and illumination geometry, and the collection of
ancillary data sets must be considered in light of the objectives of the study.
The lack of appropriate ancillary data sets often makes previously collected
data sets unusable for a new application.
Frequently, the experimental design must be modified to account for the
characteristics of the available instrumentation.