I'm trying to figure out a formula that relates latitude/longitude
to GOES pixel size. The nominal resolution is at the subsatellite
point. Alas, I do not live there, so pixel resolution is degraded
here, and I'd like to know exactly what it is.

Does anyone know of a website/formula that, given a latitude/longitude
(say, 43 N 89 W) will return a pixel size for GOES east or GOES west?
I figure it's "just" geometry, but geometry is way way way way back
in my rear-view mirror.

Thanks,

Scott (really at notscape det not)

Scott wrote:
I'm trying to figure out a formula that relates latitude/longitude
to GOES pixel size. The nominal resolution is at the subsatellite
point. Alas, I do not live there, so pixel resolution is degraded
here, and I'd like to know exactly what it is.

Does anyone know of a website/formula that, given a latitude/longitude
(say, 43 N 89 W) will return a pixel size for GOES east or GOES west?
I figure it's "just" geometry, but geometry is way way way way back
in my rear-view mirror.

Geometry indeed, but if your northern latitiude yard is on the south
side of a hill perpendicular to the view from GOES, then the loss of
resolution is simple linear distance from the satellite kinda thing. Be
sure to smile when you look up! =)

Bob Harrington wrote:
Scott wrote:

I'm trying to figure out a formula that relates latitude/longitude
to GOES pixel size. The nominal resolution is at the subsatellite
point. Alas, I do not live there, so pixel resolution is degraded
here, and I'd like to know exactly what it is.

Does anyone know of a website/formula that, given a latitude/longitude
(say, 43 N 89 W) will return a pixel size for GOES east or GOES west?
I figure it's "just" geometry, but geometry is way way way way back
in my rear-view mirror.


Geometry indeed, but if your northern latitiude yard is on the south
side of a hill perpendicular to the view from GOES, then the loss of
resolution is simple linear distance from the satellite kinda thing. Be
sure to smile when you look up! =)



chuckle Well, how 'bout I assume the Earth is a nice ol' cueball?

By the way, Today's (4-5-4) Bizarro comic is somewhat relevant -- too
bad it's not online for another 2 weeks

Scott

Scott wrote:

I'm trying to figure out a formula that relates latitude/longitude
to GOES pixel size. The nominal resolution is at the subsatellite
point. Alas, I do not live there, so pixel resolution is degraded
here, and I'd like to know exactly what it is.

Does anyone know of a website/formula that, given a latitude/longitude
(say, 43 N 89 W) will return a pixel size for GOES east or GOES west?
I figure it's "just" geometry, but geometry is way way way way back
in my rear-view mirror.


Scott - I've got a routine that computes geographic (or angular)
distance between two points on the surface of a spherical earth.
If one of the points is the satellite subpoint and the other is the
pixel position, then the law of cosines then allows you to get the third
side of the oblique triangle whose other sides are Re and (Re + H). The
law of sines then lets you get the angle opposite of (Re + H), which is
the complement of the nadir angle phi of the pixel nadir angle. The
stretching of the pixel is then proportional to 1/cos(phi) along the the
direction radiating from the subpoint.

Law of sines: a/sin(alpha) = b/sin(beta) = c/sin(gamma)

Law of cosines: c^2 = a^2 + b^2 - 2ab cos(gamma)

Let me know if you want the routine. It's in C, but easily converted.

--
____________
Grant Petty
University of Wisconsin-Madison
Browse my new book "A First Course in Atmospheric Radiation"
at http://www.sundogpublishing.com/AtmosRad.htm