Chapter 7 Field Measurements - ASD FieldSpec 3 User Manual

Chapter 7
© 2005 Analytical Spectral Devices, Inc.
Field Measurements
Field spectrometry is the quantitative measurement of radiance, irradiance,
reflectance or transmission in the field. It involves the collection of accurate
spectra and requires an awareness of the influences of:
• Sources of illumination.
• Atmospheric characteristics and stability.
• Winds.
• Instrument field of view.
• Target viewing and illumination geometry.
• Instrument scanning time.
• Spatial and temporal variability of the target characteristics.
Spectral field measurements are desirable for many reasons, not all related to
remote sensing.
• Field spectra of ground targets on the scale of the imaging sensor using
ambient solar illumination can be used to convert radiance images to
reflectance (Conel et al., 1987a & 1987b).
• Field spectra of target materials allows for more precise image analysis
and interpretation (Goetz and Srivastava, 1985).
• Field spectroscopy can perform feasibility studies to understand if and
how a process or material of interest can be detected using remote
sensing.
• Field spectra of both the material(s) of interest and spectra of other
materials present in the environment can be used to address:
» What spectral and spatial resolutions are required for detection?
» What is the best time of year/day for detection?
» What signal-to-noise ratio is required for detection?
• 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.
53 FieldSpec® 3 User Manual