VIEWZAZ

Description

Calculates the the view zenith and azimuth angles for the specified sensor type, sensor left, right, fore, and aft field-of-view angles, sensor heading and tilt angles, image dimensions, and image location.

Parameters

Name	Type	Length	Value range
Pixel Position*	Float	1 - 1	0.0 -
Line Position*	Float	1 - 1	0.0 -
Database Size*	Integer	2 - 2	1 -
Sensor Type	String	0 - 1	PUSHBROOM | WHISKBROOM Default: PUSHBROOM
Platform Tilt*	Float	1 - 1	-90.0 - 90.0
Platform Heading*	Float	1 - 1	0.0 - 360.0
Left Field-of-View Angle*	Float	1 - 1	-90.0 - 90
Right Field-of-View Angle*	Float	1 - 1	-90.0 - 90
Fore Field-of-View Angle*	Float	1 - 1	-90.0 - 90
Aft Field-of-View Angle*	Float	1 - 1	-90.0 - 90
Report	String	0 - 192	See parameter description

* Required parameter

Parameter descriptions

Pixel Position

Specifies the fractional pixel position for which the view zenith and azimuth angles will be calculated.

Line Position

Specifies the fractional line position for which the view zenith and azimuth angles will be calculated.

Database Size

Specifies, in pixels and lines, the size of the database image.

Sensor Type

Specifies the type of the sensor for which the view zenith and azimuth angles will be calculated.

If an unknown sensor type is specified, a generic view angles calculator is used, based solely on the field-of-view angles.

Platform Tilt

Specifies, in degrees, the platform tilt angle for which the view zenith and azimuth angles will be calculated. A positive tilt angle is equivalent to looking forward; a negative tilt angle is equivalent to looking backwards. A tilt angle of 0 is equivalent to looking straight down.

Platform Heading

Specifies, in degrees, the platform heading angle for which the view zenith and azimuth angles will be calculated. The heading angle is measured clockwise from North, with a heading of 0 degrees equivalent to moving North, a heading of 90 degrees equivalent to moving East, and so on.

Left Field-of-View Angle

Specifies, in degrees, the sensor left field-of-view angle for which the view zenith and azimuth angles will be calculated. A positive left field-of-view angle is equivalent to the sensor covering a swath to the left of the platform position. A negative left field-of-view angle is equivalent to the sensor covering a swath to the right of the platform position.

Right Field-of-View Angle

Specifies, in degrees, the sensor right field-of-view angle for which the view zenith and azimuth angles will be calculated. A positive right field-of-view angle is equivalent to the sensor covering a swath to the right of the platform position. A negative right field-of-view angle is equivalent to the sensor covering a swath to the left of the platform position.

Fore Field-of-View Angle

Specifies, in degrees, the sensor forward field-of-view angle for which the view zenith and azimuth angles will be calculated. A positive forward field-of-view angle is equivalent to the sensor covering a swath in front of the platform position. A negative forward field-of-view angle is equivalent to the sensor covering a swath behind the platform position.

Pushbroom and whiskbroom sensors have 0 fore and aft field-of-view angles.

Aft Field-of-View Angle

Specifies, in degrees, the sensor aft field-of-view angle for which the view zenith and azimuth angles will be calculated. A positive aft field-of-view angle is equivalent to the sensor covering a swath behind the platform position. A negative aft field-of-view angle is equivalent to the sensor covering a swath to the front of the platform position.

Pushbroom and whiskbroom sensors have 0 fore and aft field-of-view angles.

Report

Specifies where to direct the generated report.

Available options are:

• LOG: generates a report on the terminal (default)
• <modulename.RPT>: appends a report to the module's RPT file
• DISK: generates a report on file "IMPRPT.LST"

Details

VIEWZAZ is a utility that facilitates the use of the atmospheric correction system. It outputs the view zenith and view azimuth angles in degrees for a specified database size, pixel and line position, sensor type, platform heading and tilt angles, and sensor left/right/fore/aft field-of-view angles.

The view zenith angle is the angle between the observer-to-ground and observer-to-zenith directions and can vary from 0 to 180, with 180 being when the platform is directly above the observed ground position.

The view azimuth angle is the angle between the observer-to-ground and observer-to-North directions, positive clockwise from observer-to-North.