EM 1110-2-2907
1 October 2003
Are hardware and software upgrades needed? Who will finance upgrades?
Are plotters/printers available for making hardcopy maps?
Can the GIS import and process output map products?
(c) Field considerations:
What are the ecosystem dynamics? What type of field data will be re-
quired?
Will the field data be collected before, after, or during image acquisition?
Who will be collecting the field data?
What sampling methods will be employed?
What field data analysis techniques will be required?
Who will be responsible for GPS/survey control?
Who will pay for the field data collection?
Is the customer willing to help by providing new field data, existing
field data, or local expertise?
(2) Visualization Interpretation.
(a) Remotely sensed images are interpreted by visual and statistical
analyses. The goal in visualization is to identify image elements by recognizing
the relationship between pixels and groups of pixels and placing them in a mean-
ingful context within their surroundings. Few computer programs are able to
mimic the adroit human skill of visual interpretation. The extraction of visual in-
formation by a human analyst relies on image elements such as pixel tone and
color, as well as association. These elements (discussed in Chapter 2) are best per-
formed by the analyst; however, computer programs are being developed to ac-
complish these tasks.
(b) Humans are proficient at using ancillary data and personal knowl-
edge in the interpretation of image data. A scientist is capable of examining im-
ages in a variety of views (gray scale, color composites, multiple images, and
various enhancements) and in different scales (image magnification and reduc-
tion). This evaluation can be coupled with additional information such as maps,
photos, and personal experience. The researcher can then judge the nature and
importance of an object in the context of his or her own knowledge or can look to
interdisciplinary fields to evaluate a phenomena or scene.
(3) Information Extraction. Images from one area of the United States will
appear vastly different from other regions owing to variations in geology and bi-
omes across the continent. The correct identification of objects and groups of ob-
jects in a scene comes easily with experience. Below is a brief review of the
spectral characteristics of objects that commonly appear in images.
(a) Vegetation. Vegetation is distinguished from inorganic objects by its
absorption of the red and blue portions of the visible spectrum. It has high reflec-
tance in the green range and strong reflectance in the near infrared. Slight vari-
ability in the reflectance is ascribable to differences in vegetation morphology,
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