McIDAS User's Guide
Version 2017.1

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IMGRGB

Combines image and basemap into multi-banded RGB image.


Format

IMGRGB source dest BASE= FILT=GENERIC [keywords]
IMGRGB tdiff ir dest BASE= FILT=TDIFF [keywords]
IMGRGB vis ir dest BASE= FILT=VISIR [keywords]
IMGRGB wv sst dest BASE= FILT=WVSST [keywords]


Parameters

source

source ADDE dataset name and position; specify one of the following formats:

 

 

group/descriptor.position

alias.position

 

a position greater than zero represents an absolute position in the dataset; a position less than or equal to zero represents a relative position in the dataset based on image time; for example, 0 is the most recent and -1 is the next most recent; to use default position, do not specify .position (no default for group/descriptor or alias; default=0 for position)

dest

destination ADDE dataset name and absolute position; specify one of the following formats:

 

 

group/descriptor.position

alias.position

 

use only positive integers for position

tdiff

ADDE dataset containing brightness value 0-255 that correspond to surface-ir temperature values of -10 to 100K; see the Remarks

vis

ADDE dataset containing visible data

ir

ADDE dataset containing infrared data

wv

ADDE dataset containing water vapor data

sst

ADDE dataset containing sea surface temperature values; see the Remarks


Keywords

BASEmap=

generic

ADDE dataset containing single-band basemap

 

red green blue  

ADDE datasets containing red, green and blue channels of basemap

BASEThreshold=

maxium gray shade value from a basemap to be considered a map; if three datasets are specified in the BASEMAP= keyword, the value from the red channel is used for this keyword; if the gray shade value of the basemap is less than the threshold, the transparency of the source image is increased by 50%; this option is useful when a virtual graphic of a map outline has been burned into a basemap using the SVGA command (default=0)

CLOUDnocloud=

minimum brightness value for tdiff dataset to be considered a cloud; the range is 0-255 where 0 makes the basemap disappear and 255 makes the clouds disappear (default=40)

EU=

source basemap 

name of enhancement tables to apply to source and basemap images; source is used only with FILT=GENERIC and basemap is used only with BASE=generic

FILTer=

GENERIC

combines generic image and basemap; percentages of generic and basemap image are determined using the TRANSPARENCY keyword

 

VISIR 

combines visible, infrared and basemap imagery; percentages of visible and infrared data are determined by date and time of image

 

TDIFF

combines infrared and basemap imagery using surface-ir temperature differences to determine cloud/no-cloud and transparency values; see the Remarks

 

WVSST

combines water vapor, sea surface temperature and basemap imagery; transparency is determined by WV count using the enhancement table specified with WVEU keyword

IReu=

name of enhancement table to apply to infrared image when using FILT=TDIFF

NAVele=

number of elements between each navigation calculation; the range is 1-640 where higher numbers increase speed by decreasing the number of calculations, but also result in lower image quality (default=5)

SSTeu=

name of enhancement table to apply to sea surface temperature image when using FILT=WVSST (default=IMGRGB_SST.ET)

TRACKing=

YES

tracks image if allowed by the server; tracking allows commands to receive data as it's being ingested by the server; commands complete when their data request has been fulfilled; tracking is only supported on some servers (e.g., Area, GVAR and MTSAT) and it can be disabled by the server administrator

 

NO

does not track image so server only sends data that is currently available (default=value of MCTRACK environment variable; if MCTRACK is not set, default=value set by server or server administrator)

TRANSparency=

britlo brithi pctlo pcthi

transparency values to assign low and high brightness levels when using FILT=GENERIC; if the value for pctlo is greater than 0, brightness values 0 to britlo are assigned transparency values 0 to pctlo; if the value of pcthi is less than 100, brightness values brithi to 255 are assigned transparency values pcthi to 100 (default=0 255 0 100)

WVeu=

name of enhancement table to apply to water vapor image when using FILT=WVSST (default=IMGRGB_WV.ET)


Remarks and Examples

The topography, land/sea mask and NASA's Blue Marble Next Generation images for use with this command are available at the McIDAS Website at http://www.ssec.wisc.edu/mcidas/basemaps/

All source and basemap images must be the same size and cover the same geographical region.

Each option for the FILTER keyword is described below with an example.

 

GENERIC

This option uses a generic image with a basemap. With the TRANSPARENCY keyword the percentages of these two images is determined. The following example combines a NEXRAD image with NASA's Blue Marble Next Generation basemap.

IMGCOPY NEXRAD/BREF1 A/A.4000 ID=ARX SIZE=ALL
IMGCOPY A/A.4000 A/A.4001 SIZE=ALL
IMGCOPY A/A.4000 A/A.4002 SIZE=ALL
IMGCOPY A/A.4000 A/A.4003 SIZE=ALL


These commands copy the NEXRAD image into an AREA file, then create 3 other AREA files with the same size and geographical region.

IMGREMAP BBM/RED A/A.4001 PRO=DEST
IMGREMAP BBM/GREEN A/A.4002 PRO=DEST
IMGREMAP BBM/BLUE A/A.4003 PRO=DEST


These commands remap each Blue Marble Next Generation image component into the same region.

IMGRGB A/A.4000 A/A.4005 BASE=A/A.4001 A/A.4002 A/A.4003 FILT=GENERIC EU=BREF TRANS=16 255 95 100
IMGDISP A/A.4005 1 BAND=1
IMGDISP A/A.4005 2 BAND=2
IMGDISP A/A.4005 3 BAND=3
COMBINE 0 1 2 3


The IMGRGB combines the NEXRAD image with the basemaps with a specific transparency and a radar enhancement table. The IMGDISP commands and COMBINE command are used to display the resultant image, a radar display over a basemap.

 

VISIR

This option uses the date and time of the imagery to determine the percentages of visible and infrared to be used. The transparency is determined by combining the visible and infrared image information where warm/dark pixels are very transparent and cold/bright pixels are very opaque. This set of examples combines a topographic basemap with visible and infrared imagery.

IMGOPER BASEMAP/TOPOLAKES MY/AREAS.1 SIZE=2000 4000 MAG=-5 SCALE=0 6000 0 253

To create the basemap, you have to first decide on an elevation range then use IMGOPER to reduce the 2-byte data to 1-byte. The highest point in North America is roughly 6000 meters, so this IMGOPER scales the global basemap.

IMGREMAP MY/AREAS.1 MY/AREAS.2 STATION=KSTJ RES=11 PRO=SIN

This command remaps the basemap to a North American domain.

IMGREMAP EAST/FD MY/AREAS.4 STATION=KSTJ RES=11 BAND=1 TIME=17:45 PRO=SIN
IMGREMAP EAST/FD MY/AREAS.5 STATION=KSTJ RES=11 BAND=4 TIME=17:45 PRO=SIN


These commands remap the visible and infrared images over the desired domain. 
 
IMGRGB MY/AREAS.4 MY/AREAS.5 MY/AREAS.6 BASEMAP=MY/AREAS.2 FILT=VISIR EU=X TOPO
IMGDISP MY/AREAS.6 1 BAND=1
IMGDISP MY/AREAS.6 2 BAND=2
IMGDISP MY/AREAS.6 3 BAND=3
MAP GRA=1-3
COMBINE 0 1 2 3
FRMSAVE 0 vis-ir-example.jpg TYPE=COMBINE FORM=JPG

The IMGRGB combines the basemap and satellite imagery with a topography enhancement. The IMGDISP, MAP and COMBINE commands are used to display the resultant image. The FRMSAVE saves the image as a 24-bit jpeg file.

 

TDIFF

This option uses the tdiff image to determine a cloud/no-cloud threshold and to determine the transparency of the infrared imagery on top of a basemap. The tdiff image, which must be created prior to running this command, must have brightness values 0-255 corresponding to surface-infrared temperature difference values -10 to 100. For example, commands like those below can be used to create the tdiff image.

GRDIMG RTGRIDS/NAM-USLC MY/AREAS.1 PARAM=T LEV=SFC DAY=#Y TIME=12 FHOUR=0 UNIT=K SCALE=320 200 0 255 MAG=10 10
IMGREMAP MY/AREAS.1 MY/AREAS.11 RES=8 PRO=SIN STA=KSTJ SIZE=600 800
IMGREMAP EASTL/CONUS MY/AREAS.2 BAND=4 RES=8 PRO=SIN STA=KSTJ TIME=11:45 SIZE=600 800
IMGOPER MY/AREAS.2 MY/AREAS.12 PROD=T UNIT=TEMP SCALE=320 200 0 255 SIZE=600 800
IMGOPER MY/AREAS.11 MY/AREAS.12 MY/AREAS.13 UNIT=T T FORM=ADD SCALE=-10 100 0 255 COEF=1 -1
SIZE=600 800

Once this image is created, this example can be used to create the infrared and basemap imagery using the surface-ir temperature differences.

IMGREMAP BBM/RED MY/AREAS.20 RES=8 PRO=SIN STA=KSTJ SIZE=600 800
IMGREMAP BBM/GREEN MY/AREAS.21 RES=8 PRO=SIN STA=KSTJ SIZE=600 800
IMGREMAP BBM/BLUE MY/AREAS.22 RES=8 PRO=SIN STA=KSTJ SIZE=600 800


These commands remap each Blue Marble Next Generation image component into a 600 by 800 sized AREA file in sinusoidal projection centered over St. Joseph, MO.

IMGRGB MY/AREAS.13 MY/AREAS.2 A/A.4005 FILT=TDIFF BASEMAP=MY/AREAS.20 MY/AREAS.21 MY/AREAS.22
IMGDISP A/A.4005 1 BAND=1;MAP
IMGDISP A/A.4005 2 BAND=2;MAP
IMGDISP A/A.4005 3 BAND=3;MAP
COMBINE 0 1 2 3


The IMGRGB combines the satellite imagery and temperature difference image over the basemaps. The IMGDISP commands and COMBINE command are used to display the resultant image, the GOES infrared imagery over the basemap.

 

WVSST

This option requires that you create a sea surface temperature image before running the command. Land values in the SST image must have a value of 0. The default enhancement table for SSTEU= assumes that SST temperature values 270 to 305 correspond to gray shades 0 to 149.  Transparency values are determined by brightness values of the water vapor image and, if present, the enhancement table specified with WVEU=. The enhancement table should stretch only gray shades (i.e., do not use colors). This example uses a GOES water vapor image, the land/sea mask image, and gridded SST data.

IMGREMAP EASTS/CONUS A/A.4000 BAND=3 PRO=SIN STATION=KSTJ RES=11 SAVE=YES TIME=12 18
GRDIMG RTGRIDS/SST-GLME2 A/A.4004 MAG=5 SCALE=270 305 0 149 PARAM=TWAT  DAY=#Y
IMGREMAP A/A.4004 A/A.4001 PRO=SIN STATION=KSTJ RES=11 SAVE=YES


These commands remap the GOES water vapor image and SST grid into common size and region (sinusoidal projection with the resolution of 11 km).

IMGREMAP BASEMAP/LSMASK A/A.4002 PRO=SIN STATION=KSTJ RES=11 SAVE=YES
IMGFILT A/A.4001 A/A.4002 A/A.4003 FILT=DIS 0 255 8 8 0 SCALE=0 255 0 255 SIZE=ALL


After remapping the land/sea mask image into the desired domain, the IMGFILT combines the land/sea mask with the SST image which leaves the land black and the appropriate sea surface temperatures over the water.

IMGRGB A/A.4000 A/A.4003 A/A.4005 FILT=WVSST BASEMAP=A/A.4100 A/A.4101 A/A.4102
IMGDISP A/A.4005 1 BAND=1;EG;MAP
IMGDISP A/A.4005 2 BAND=2;EG;MAP
IMGDISP A/A.4005 3 BAND=3;EG;MAP
COMBINE 0 1 2 3


The IMGRGB takes the SST image (with the land masked out) and combines it with the water vapor image. The IMGDISP commands and COMBINE command are used to display the resultant image.


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