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[McIDAS #MMD-610472]: 20140718: Problem matching projections between McIDAS and Terascan

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  • Subject: [McIDAS #MMD-610472]: 20140718: Problem matching projections between McIDAS and Terascan
  • Date: Mon, 21 Jul 2014 13:15:48 -0600
Hi Greg,

re: what is the source dataset (so I can try to replicate your example)

> The source dataset is EAST/CONUS.

OK.  This should help.

re:
> Just plot the any image from that
> source. The problem is the Mercator projection at 1km resolution from
> McIDAS doesn't look like its the right plot area. The Terascan plot covers
> the area I would expect from a Mercator plot at 1km resolution. I don't
> know how to make the McIDAS plot match the Terascan one.

I think that the difference you are seeing is related to the 'slat' positional
parameter for the PRO=MERC keyword sequence.  You are specifying an 'slat' of
'0' (zero, which is the default):

imgremap.k $sdset $ddset.$dpos TIME=$time LATLON=$latlon PRO=MERC 0 RES=$res 
SIZE=$lin $ele SSIZE=ALL BAND=$band

If you change 'slat' to 39.25 (the center of the remapped image), the areal
coverage is noticeably different:

imgremap.k $sdset $ddset.$dpos TIME=$time LATLON=$latlon PRO=MERC 39.25 
SIZE=$lin $ele SSIZE=ALL BAND=$band

Question:

- do you know what Terascan is using for its Mercator parameters?

I wouldn't be surprised if the standard latitude used in the Terascan algorithm 
is
the center latitude of the remapped image.

Please give the following a try and let me know if the results look more like
what you are expecting:

$res = 1
$lat = 39.25
$lon = 105.00
$lin = 925
$ele = 1050
$band = 1

imgremap.k $sdset $ddset.$dpos TIME=$time LATLON=$lat $lon PRO=MERC $lat 
SIZE=$lin $ele SSIZE=ALL BAND=$band

Cheers,

Tom
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Ticket Details
===================
Ticket ID: MMD-610472
Department: Support McIDAS
Priority: Normal
Status: Closed