shade Documentation

shade - Create shaded-relief cube from topographic cube
SHADE can be used to create a cube that looks approximately like an
aerial photograph of the topographic cube.  The sides of hills will be
shaded or brightened depending on the sun direction, but no shadows will
be cast.  This can be used to get an impression of the shape of the
land.  Other data besides topography, such as gravity or magnetic data,
can be used in this program, as long as it is a continuous data set.

Certain keywords must exist on the cube labels for this program to run.
CORE_UNIT must be METER, KILOMETER or FOOT and defines the vertical
resolution.  If the cube is in a map projection and has valid mapping
labels, the next two keywords are not needed.  HORIZONTAL_UNIT must be
METER, KILOMETER or FOOT.  HORIZONTAL_SCALE is the distance between the
center points of two pixels.  For example:  for HORIZONTAL_UNIT =
KILOMETER, HORIZONTAL_SCALE = 0.1, the resolution of the cube is 0.1
km/pixel.

SHADE computes reflectance given any sun elevation and one of eight sun
directions using the Lommel-Seeliger law:

	Reflectance=1/(1+cos(E)/cos(I))

Where: E=the angle between the observer and the slope normal
       I=the angle between the sun and the slope normal

For this application the observer is at 90 degrees (vertical) and the
sun direction=0, 45, 90, 135, 180, 225, 270 or 315 degrees.

For more detail on shaded-relief cubes see the reference:

   Batson, R. M., Edwards, Kathleen, and Eliason, E. M., 1975,
      Computer-generated Shaded-relief Images: U.S. Geological
      Survey Journal of Research, Vol 3, No. 4, p. 401-408.

PROGRAMMER: Kay Edwards, USGS, Flagstaff, AZ

Input cube file name
(Default extension is .cub)

NONE

Input subcube specifier

--

Output cube file name
(Default extension is .cub)

NONE

Sun angle from horizon

NONE

Sun direction (T-B,etc)
(Top to Bottom,etc)

L-R

Vertical exaggeration

1.0

Output pixel type

1

Minimum and maximum
output pixel range

-0.5,0.5

ADDITIONAL NOTES:

Parm	Description
FROM	Input cube file name. If the file extension is omitted, then ".cub" will be assumed.
SFROM	SFROM specifies the subcube using a single string for all three dimensions of the cube. The order of the three dimensions is always "samples:lines:bands". If a dimension is left blank, all the data for that dimension is selected. The default value of NULL for SFROM selects the entire cube. Any application below can be used for any dimension. To select specific data from any dimension: "10-100(3):11,12,15-20:1-10(2)" = This example will select every third sample starting with sample 10 thru 100. It selects lines 11 and 12, and 15-20. It selects every other band, starting with band 1 thru 10. There are special characters that can be used for selecting a subcube efficiently, such as "*","#", and "~". For examples type "help sfrom" in TAE. **NOTE** For more examples and explanations of the many features of the SFROM parameter, tutor the sfrom.pdf or refer to Introduction to ISIS, Section 6, of the ISIS User's Manual.
TO	Output cube file name. If the file extension is omitted, then ".cub" will be assumed.
SUN	For SUN=90, the sun is directly overhead. For SUN=0, the sun is on the horizon.
DIRC	A code is used to indicate the direction the sun is coming from. Eight codes are defined: L-R Left to right TL-BR Top left to bottom right T-B Top to bottom TR-BL Top right to bottom left R-L Right to left BR-TL Bottom right to top left B-T Bottom to top BL-TR Bottom left to top right
EXAG	This parameter can be used to exaggerate the shaded-relief effect. A value greater than 1 will make the slopes appear steeper.
OTYPE	Output pixel data type. Permitted values are: NULL = output type is same as input file pixel type 1 = 8-bit (integer with type conversion parameters) 2 = 16-bit (integer with type conversion parameters) 3 = 32-bit (floating point) When processed data are being written back into the input file, the output pixel type must be the same as the existing pixel type in the input file.
ORANGE	Output pixel data range. If ORANGE is NULL, then the CORE_BASE and CORE_MULTIPLIER in the output file will be set to represent the same range of data as the input file. For this application, the output range of data will be from -0.5 to +0.5. Depending on the sun angle and vertical exaggeration, the data may not cover this full range. If OTYPE=1 (8-bit) or OTYPE=2 (16-bit), then the CORE_BASE and CORE_MULTIPLIER in the output file will be set to values that allow representing the specified range of output values. Output values outside this range will be stored as a special "representation saturation" value. The ORANGE parameter is ignored if OTYPE=3 (32-bit), because the CORE_BASE and CORE_MULTIPLIER are not applicable to floating point pixel values. **NOTE** For a more detailed explanation of ORANGE, tutor the orange.pdf.