NORTEL

Two channel image combination

Format

NORTEL sarea1 sarea2 darea (keywords)

Parameters

sarea1	first source AREA number
sarea2	second source AREA number
darea	destination AREA number

Keywords

3D = YES	invokes the 3-d mode
PD = value	specify maximum pixel displacement for 3-d (def: 32)
D1 = min max	destination range of values for sarea1 (def: 0 127)
D2 = min max	destination range of values for sarea2 (def: 128 255)
S1 = min max	source range of values for sarea1 (def: 0 255)
S2 = min max	source range of values for sarea2 (def: 0 255)
T1 = min max	sarea1 thresholds for substituting values (def: S1 range)
T2 = min max	sarea2 thresholds for substituting values (def: S2 range)
REPLACE=NO/YES	always use pixels from sarea2 if within T2 thresholds otherwise use pixels from sarea1 (default=NO)

Remarks:

Produces a pseudo dual-channel image combination by rescaling two AREA files into two separate brightness ranges creating a new AREA file that consists of pixel values from the two source AREAs.

In order to combine two images the source areas must,

be exactly the same size o cover the same geographic areas
be in the same projection

S1/S2 and D1/D2 are used to change the scaling (scaling is linear); S1/S2 specify the input range; D1/D2 specify the output range.

By default, all of the first source AREA's ('sarea1') brightnesses (0-255) are scaled 0-127. All of the second AREA's ('sarea2') brightnesses (0-255) are scaled to 128-255.

T1/T2 values are used to define the substitution of values for any pixel in the output AREA (darea) that would come from 'sarea1' but where the value in 'sarea1' is outside the range specified in T1, the appropriately scaled value from 'sarea2' will be used instead. REPLACE=YES requests that 'sarea2's brightnesses will always be put into 'darea' IF they fall within the T2 threshold values. If they don't fall within the T2 values, then 'sarea1's values are used.

Use the EU command to color each channel separately after 'darea' is displayed.

For 3-D (false color stereo), 'sarea1 should be a visible image, while 'sarea2' should be the corresponding IR.

In this case, assuming no change in output mapping, use these EU commands to set the correct enhancement for viewing thru green/red glasses:

EU MAK 0 127 BLACK GREEN; EU MAK 128 255 BLACK RED

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