Re: [cf-satellite] related to scanning direction

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Hi.

The scan direction for POES-type satellites (for the AVHRR, MODIS, and VIIRS 
sensors, at any rate) is "across-track".  The ground footprint of a scan line 
is hardly ever (maybe never) coincident with any longitude or latitude line, 
does not describe a straight line, and changes from being close to parallel 
with the Earth's equator at the ascending/descending nodes to being close to 
parallel with longitude lines at the northern/southern-most points of each 
orbit.  The direction of scan can be "right-to-left" or "left-to-right" as seen 
from the satellite looking down at the Earth.

The imaging satellites (SPOT, QuickBird, WorldView, Geo-Eye, etc) typically use 
push-broom sensors that don't have rotating telescopes.  They may or may not be 
steerable in relation to the satellite track.  And then there are the 
geo-synchronous satellites...

All that just to point out that a proper vocabulary for describing such things 
is not simple, and we need to be careful not to go with a simplistic solution.

Grace and peace,

Jim

Jim Biard
Research Scholar
Cooperative Institute for Climate and Satellites
Remote Sensing and Applications Division
National Climatic Data Center
151 Patton Ave, Asheville, NC 28801-5001

jim.biard@xxxxxxxx
828-271-4900

On Aug 16, 2012, at 12:39 AM, ghansham sangar wrote:

> R/Sir
> 
> I have a query related to something scanning direction.
> Are there any conventions in CF that denote in which direction the scanning 
> is happening.
> Generally all the geostationary and POES satellites scan along the latitude 
> lines. 
> But there are some satellite specially designed for tropical region where we 
> see that they scan along
> the longitude lines. Are there any ways to denote that. I think if it is not 
> there, then we should include 
> them somewhere.
> regards
> Ghansham
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