McIDAS-X User's Guide
Version 2021.1

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MCSTRETCH

This keyword specifies whether to request the expanded stretch option with image data. The keyword can also be specified as MCS= (as well as MCSTRETCH=).

MCSTRETCH=

EXP

requests use of the expanded stretch option to increase the detail shown in specific visible, water vapor and short-wave infrared imagery when displayed with IMGDISP or copied to a 1-byte Area file using commands like IMGCOPY with STYPE=VISR or IMGREMAP; this option is available in McIDAS-X versions 2017.2 and later, and requires that the image matches one of the satellite and band combinations in the file MCSTRETCH.TXT (run command SEE MCSTRETCH.TXT to view the file)

 

ORIG

requests use of the original stretch option that was used in all McIDAS-X versions prior to 2017.2; see the file MCSTRETCH.TXT for the ranges used in both the ORIG and EXP options

The default (if you don't specify this keyword) is to use the method set in the MCSTRETCH environment variable; if it is not set, EXP is assumed. So unless you set the environment variable to MCSTRETCH=ORIG or specify it as a keyword in your IMG* command, the expanded stretch option is used. Likewise, if you change the environment variable setting to MCSTRETCH=ORIG you must specify keyword MCSTRETCH=EXP in your IMG* command to request the expanded stretch option. See Setting the Expanded Stretch Option for more information.

Below are two examples.

IMGDISP GOES16/CONUS BAND=9 MCSTRETCH=EXP

This entry displays band 9 of image GOES16/CONUS while also requesting use of the expanded stretch option. The satellite and band combination matches an entry in the MCSTRETCH.TXT file so if GOES16/CONUS is a local file or is on a server running McIDAS-X 2017.2 or later it is displayed using the expanded stretch option to provide more detail in both the colder and warmer temperatures of this water vapor band. If you replace MCSTRETCH=EXP with MCSTRETCH=ORIG the image is displayed using the original stretch option so it appears the same as it would if displayed in McIDAS-X 2017.1 or earlier.

IMGCOPY HIMAWARI/FD LOCAL/HIM8 BAND=3 STYPE=VISR MCS=EXP

This entry copies band 3 of image HIMAWARI/FD to local dataset LOCAL/HIM8 while also requesting use of the expanded stretch option. The satellite and band combination matches an entry in the MCSTRETCH.TXT file so if HIMAWARI/FD is a local file or is on a server running McIDAS-X 2017.2 or later it is copied using the expanded stretch option to provide more detail in the higher reflectances by expanding the range of those data values over a larger range of 8-bit brightness values. If you replace MCS=EXP with MCS=ORIG the image is copied using the original stretch option so the output Area file has the same data values as it would if IMGCOPYed in McIDAS-X 2017.1 or earlier.


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