McIDAS User's Guide
Version 2018.1
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Remaps images into different projections.
IMGREMAP sdataset ddataset [keywords]
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sdataset |
source ADDE dataset name and position; specify one of the following formats: |
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group/descriptor.position
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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) |
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ddataset |
destination ADDE dataset name and absolute position; specify one of the following formats: |
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group/descriptor.position
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use only positive integers for position |
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DAY= |
selects from sdataset images with the specified day |
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DISt= |
maximum distance, in kilometers, from the satellite subpoint to include in the remap; use SMOOTH=YES and/or SPLINE= with a smaller value to round the edges of the output image |
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ID= |
selects from sdataset images with the specified NEXRAD station ID, e.g., MKX |
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MAG= |
lmag emag |
line and element reduction factor to apply to the source data before it's remapped; valid range is 1 through -999 where 1, 0, and -1 mean no reduction, -2 means a 2x reduction, etc; see the Remarks (lmag default=1, emag default=lmag) |
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SSIze= |
line element |
size of the source image region to remap; the region consists of the specified number of lines and elements centered at the location specified in the LATLON or STATION keyword (default=computed; see the Remarks) |
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ALL |
remaps the entire source image, even if only a small subset of the data is actually saved in the destination image with the SIZE keyword |
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TIMe= |
btime etime |
selects from sdataset images within the specified time range |
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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 |
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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) |
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BANd= |
image band number to remap (default=existing band for single-band images; no default for multiband images) |
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CF= |
YES |
creates a CF-compliant netCDF file (default) |
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NO |
creates a netCDF file in the previous (pre-2009.2) format, which is not CF-compliant; the CF=YES/NO keyword is valid only when writing to netCDF format destination datasets; it is ignored when writing to datasets of other formats |
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LATlon= |
clat clon |
center latitude and longitude for ddataset (default=center latitude and longitude of sdataset) |
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MERge= |
NO |
sdataset data overwrites the entire ddataset (default) |
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YES |
sdataset data overwrites ddataset only where images overlap; valid only with PRO=DEST |
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NAVtype= |
LALO linc einc |
use lat/lon navigation instead of the regular (native) navigation; this keyword is valid only if the source image is area or AVHRR Level 1b format; linc and einc specify the image line and element increments, e.g., NAVTYPE=LALO 4 3 requests lat/lon nav using the data from every fourth line and every third element (default=use native nav; if you specify LALO, lat/lon nav is used and the linc and einc defaults are the computed values that result in using the largest number of data points allowable without exceeding the max size of the AUX block) |
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PRO= |
DEST |
use the navigation of ddataset; see the Remarks for requirements (default) |
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LAMB |
slat1 slat2 slon
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slat1 |
standard latitude (default=30) |
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slat2 |
standard latitude (default=50) |
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slon |
standard longitude (default=center longitude) |
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MERC |
slat |
Mercator projection; specify standard latitude (default=0) |
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MOLL |
slon |
Mollweide projection; specify standard longitude (default=0) |
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PS |
slat slon
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slat |
standard latitude (default=60) |
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slon |
standard longitude (default=center longitude) |
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RADAR |
rot |
radar projection; specify rotation angle (default=0) |
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RECT |
rectilinear projection |
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SIN |
sinusoidal equal area projection |
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TANC |
slat slon
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slat |
standard latitude (default=30 if the center latitude is in the northern hemisphere; -30 if the center latitude is in the southern hemisphere) |
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slon |
standard longitude (default=center longitude) |
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RES= |
resolution of ddataset in km; not valid with PRO=DEST (default=1) |
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SAVesrc= |
YES |
writes sdataset's directory information (including SS, DATE, TIME and BAND) to ddataset; valid only with PRO=DEST (default=NO) |
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SIZe= |
line ele |
number of lines and elements in ddataset; the ele value must be a multiple of 4; SIZE is not valid with PRO=DEST (default=480 640) |
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ALL |
creates an image large enough to include the entire geographical coverage of sdataset |
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SMOoth= |
limb data provides limb or data smoothing |
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limb |
NO |
no limb smoothing (default) |
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YES |
provides limb smoothing |
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data |
NO |
no data smoothing (default) |
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YES |
provides data smoothing using a 2/3:1/3 weighting of the two closest pixels |
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SPLine= |
spline size in image pixels; the range is from at least 1 to 100; the range minimum may be computed based on source data (default=20) |
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STAtion= |
station ID to place at the center of the remapped image; specify as the ID, e.g., KMSN or YSSY, optionally followed by the station type in brackets, e.g., ARX[N] or ARX[V]; see the TYPE keyword in the STNLIST command for valid station types |
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WL= |
remaps band with image wavelength closest to the specified value; valid only with high spectral resolution data, e.g., Aqua AIRS |
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WN= |
remaps band with image wave number closest to the specified value; valid only with high spectral resolution data, e.g., Aqua AIRS |
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IMGREMAP subdivides the destination image into boxes. The height and width of each of the boxes is determined with the SPLINE keyword, which defaults to 20 pixels. IMGREMAP performs a navigation transformation from line/element to latitutde/longitude at each of the spline box corners. It then determines the line/element coordinates in the source image that correspond to these same latitude/longitude values. Those corner values are used in a bi-linear interpolation scheme (which is much faster than a navigation transformation) to compute the line/element coordinate of each source image pixel it will use to fill the intermediate points in the spline box. This method ensures that each pixel in the destination image has an associated pixel from the source image.
If the destination image is lower resolution than the source image, the data are sampled. If the destination image is higher resolution, the pixel values are replicated. Only the 8-bit grayscale values are stored in the destination image. By default, there is no interpolation of the 8-bit values; however, the keyword SMOOTH=X YES performs an interpolation using a 2/3:1/3 weighting of the two closest pixels.
IMGREMAP uses the sdataset parameter and the DAY, TIME and ID keywords to select the source image to remap. It uses the Output Keywords to calculate the geographical region to extract from the source image for the remap. The calculation, however, sometimes underestimates or overestimates the size of the source image region needed for the remap. If that happens, use the SSIZE keyword to override the default calculation. For example, if the default calculation doesn't include the poles in the remap of a global image, specify SSIZE=ALL to ensure that they're included. The default calculation often overestimates the data region needed for a remap of polar-orbiting satellite data. To avoid this, you can use SSIZE with line and element values to choose a smaller source image region. Selecting more source image data than necessary does not affect the output image, but takes it longer to complete and adds to the cost if you pay for the data.
The MAG keyword can be used to further reduce the amount of source image data that is extracted and remapped. Use the MAG keyword only when specifying a destination image with less detail (lower resolution) than the source image. For example, if the source image is 1km resolution and you specify RES=30 for a 30km resolution destination image, you can also specify MAG=-16 to reduce the amount of data extracted and remapped by a factor of 16. It's best to pick a MAG value somewhat less than the destination image resolution because the quality of the destination image decreases as the MAG value approaches the resolution value.
When using MERGE=YES, all data in the source image (even pixels with zero data values) overwrite the collocated data in the destination image. Thus, all geographic locations in the destination image that are also in the source image will be replaced by the source image's values.
The radar projection is identical to the sinusoidal equal area projection, except that it allows you to rotate the destination image.
Display destination images with the IMGDISP command.
For IMGREMAP to be successful using the PRO=DEST option, the following requirements (with the corresponding IMGLIST FORM=ALL output values in parenthesis) must be met:
To create a destination dataset with a line prefix length and validity code of zero, use the IMGCOPY command with the keyword STYPE=VISR and SIZE=line ele; do not use SIZE=SAME.
You can use IMGREMAP to create a netCDF image file. To do so, the destination dataset must be NCDF-format and IMAGE-type. See the Remarks section in the DSSERVE command for more information.
IMGREMAP LOCAL/IMAGE.16 LOCAL/REMAP.4000
This entry remaps the image data in position 16 of dataset LOCAL/IMAGE into position 4000 of dataset LOCAL/REMAP. The source image replaces the destination image but uses its projection information.
IMGREMAP NOAA-12/HRPT NO-GOES/DATA.10 MERGE=YES PRO=DEST
This entry remaps the most recent image in dataset NOAA-12/HRPT into position 10 of dataset NO-GOES/DATA. The source image uses projection information from the destination image and replaces data only where the images overlap.
IMGREMAP G8/FDV G8/REMAP.1 RES=24 PRO=SIN
This entry remaps the most recent image in the G8/FDV dataset into the position 1 of dataset G8/REMAP. The destination image is remapped with a resolution of 24 kilometers in a sinusoidal equal area projection.
IMGREMAP G8/CONUSV G8/RADAR.2 RES=4 STATION=BOS PRO=RADAR 45
This entry remaps the most recent image in the G8/CONUSV dataset into position 2 of dataset G8/RADAR. The destination image is remapped in a radar projection, rotated 45 degrees. The image is centered at Boston, MA and has a resolution of four kilometers.
IMGREMAP WV.4 REMAP.4 PRO=LAMB 30 60 70 LATLON=34 78 RES=4
This entry remaps the image in position 4 of the dataset with the alias WV into position 4 of the dataset with the alias REMAP. The destination image is centered at 34° N and 78° W and has a resolution of 4 kilometers. The image is remapped in a Lambert conformal projection using standard latitudes of 30° and 60° N and a standard longitude of 70° W.
IMGREMAP GOES.1 A.2 PRO=PS 45 71 RES=4 SPLINE=40
This entry remaps the image in position 1 of the dataset with the alias GOES into position 2 of the dataset with the alias A. The destination image is remapped in a polar stereographic projection, with a standard latitude of 45° N and a standard longitude of 71° W. The resolution of the remapped data is four kilometers, and the spline value is 40.
IMGREMAP A/A.8016 A/A.4000 PRO=MERC 50 RES=2 SIZE=ALL
This entry remaps all of the image data in position 8016 of dataset A/A into position 4000 of dataset A/A. The destination image is as large as necessary to contain the entire remapped image: a Mercator projection, with a standard latitude of 50°N and a resolution of two kilometers.
IMGREMAP GOES/VIS LOCAL/AREA.23 BAND=1 DAY=#Y TIME=22:55 23:05 MAG=-8 RES=16 PRO=MERC LATLON=0 90
This entry remaps the image in dataset GOES/VIS with today's date and an image time between 22:55 and 23:05 into position 23 of dataset LOCAL/AREA. The destination image is in a Mercator projection centered at 0°N and 90°W with a resolution of 16 kilometers. The MAG=-8 keyword reduces the resolution of the data retrieved from the source image from 1km to 8km before remapping it to 16km resolution. This 8x reduction speeds up completion of the command with little effect on the quality of the destination image.
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