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20050819: GeoTIFF to AREA conversion (cont.)



>From: "Valentijn Venus" <address@hidden>
>Organization: ITC
>Keywords:  200508172300.j7HN0Bjo011078 McIDAS MAKEAREA MAKNAV BSQ

Hi Valentijn,

>this certainly is more than a 'how to', for which many thanks also on
>behalf of my students Raul Cumba. He works for the early wanring unit
>for FAO in Maputo, Mozambique.

No worries.  You caught me at a good time :-)

>We're planning for a field campaign in
>Burkina, and the land cover map -> emmissivities will be used to feed a
>Land Surface Temperature estimation method as proposed by Pinker and
>Sun (1999?).

Interesting!

>Now on the projection, at the web site of NASA
><http://edcdaac.usgs.gov/1KM/goodesarticle.html>  more details are
>given for the Goode Homolosine projection, which in fact is a composite
>map projection that merges the Mollweide projection for higher
>latitudes and the Sinusoidal projection for lower latitudes (Goode
>1925).

I knew this from a discussion I had with a professor at the University
of Nebraska-Lincoln.  What I do not know is where the split is.

>i guess the MAKENAV command should also work for this projection
>if you restrict it to either of the two.

Yes, it should.  The key is in knowing where the split is and how
the split is done.  The URL you provided above gives us the split
location:

"The two projections join at 40 44'11.8" North and South"

>I don't have a McIDAS version
>on my home computer, but i guess for something close to the equator it
>should look something like this: MAKNAV SIN=

Yes, for the lower latitude portion only.

>What are your thoughts on this?

I guess that you could add the sinusoidal navigation for the low
latitude projection and then use IMGOPER to extract the image portion
that corresponds to, then do the same for the high latitude piece using
the Mollweide projection.  You would then end up with two images of
different projections that you could merge together using IMGREMAP.
The question is what does this buy you when the image is also available
in the Lat,Lon (RECT=) projection?

About the size limitation of the image:  If you want to get 1 km
images from the global one, all you need to do is write a simple program
that will read the 1 km BSQ image and split it so that the total number
of elements in each piece is small enough.

The sectorization work has, however, already been done for you -- use
the Lat,Lon BSQ image for Africa.  It is small enough to use directly;
here is the metadata:

Information Image Size:         9955 Pixels 9561 Lines
Quantization:                   8-bit unsigned integer
Output                          Georeferenced Units:LONG/LAT E019
Projection:                     Geographic (geodetic)
Earth Ellipsoid:                Sphere, rad 6370997 m
Upper Left Corner:              26d22'30.00" W Lon 38d10'30.00" N Lat
Lower Right Corner:             56d35'00.00" E Lon 41d30'00.00" S Lat
Pixel Size (in Degrees):        0.00833 Lon0.00833 Lat
(Equivalent Deg,Min,Sec):       0d00'30.00"0d00'30.00"
UpLeftX:                        -2.63750000000000E+01
UpLeftY:                        3.81750000000000E+01
LoRightX:                       5.65833333333333E+01
LoRightY:                       -4.15000000000000E+01

Cheers,

Tom
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