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:: [FA-1 TOPOGRAPHIC ANALYSIS]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: VISIBILITY AND SHADOW STATE OF STEEP SLOPES IN STEREO-OBSERVATION OF SIDE-LOOK SPOT IMAGERY. JAN J. NOSSIN

Document type:: Multivolume work

Structure type:: Chapter

VISIBILITY AND SHADOW STATE OF STEEP SLOPES IN STEREO-OBSERVATION OF SIDE-LOOK SPOT IMAGERY JAN J.NOSSIN International Institute for Aerospace Survey and Earth Sciences ITC Enschede, the Netherlands. ABSTRACT: In side-look SPOT imagery, slopes steeper than the complement of the incidence angle, exposed in the lookdirection, are not visible to the satellite, and hence, not imaged. A method has been developed to determine the (non)visibility of slopes in other exposure directions (Nossin, 1990). Similarly, slopes steeper than the sun elevation angle are in shadow, if exposed in the (azimuth + 180°) direction, and a method to calculate the sunlit/shadow condition of other slope exposure directions has been developed. The presence or absence of a slope can, practically, only be determined in ster eo-imagery; throughout this paper therefore, we presume the context of stereo observations. Strong westlook imagery may not show steep west-facing slopes, whether sunlit or shadowed, and the arc over which this occurs for corresponding slope angles, is determined. Slopes with an eastward exposure component are generally all sunlit, but slopes with a slope angle > (90°- incidence angle) are not visible to the satellite on left-look (i.e: eastlook) images. On eastlook imagery, in general, slopes with a westward exposure component are visible; slopes steeper than the sun elevation angle are in shadow, and visible. The contrast in eastlook imagery therefore, in general is more pronounced than in westlook imagery. Annexed to this paper, two versions are presented of a computer programme that calculates the (in)visibility of slopes with specified slope angles and their exposure directions, and also the state of shadow or sunshine on the slope. It does this calculation for any combination of lookdirection, incidence angle, sun azimuth and sun elevation. In the first program, named Iglospot, a semi-graphic output of slope visibility and shadow is provided in steps of 5° for slope angles and exposure directions. In the second program, named Spotslopes, a tabular output of invisible and of shadowed slopes is provided in steps of one degree. Both programs are written in Pascal; users could simply retype one or both and use it after compilation on any machine using standard Pascal. The retyping should be done very exactly. This sidelook effect is important as an interpretability factor.

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