== Computed overpass times for NC Landsat dataset ==

https://grass.osgeo.org/download/sample-data/

--> http://www.grassbook.org/wp-content/uploads/ncexternal/landsat/
    1987, 2000, 2002

PROBLEM: the overpass time is not properly recorded in the .met files.

SOLUTION:
Overpass times derived from http://cloudsgate2.larc.nasa.gov/cgi-bin/predict/predict.cgi

sat                date       long          lat (in WGS84)   resolution (km)  day only
Landsat 5     14-Oct-1987     -78.69149946  35.74853512      4                yes
Landsat 7     31-Mar-2000     same          same             4                yes
Landsat 7     24-May-2002     same          same             4                yes

Coordinates are from center scene, and reprojected from llc/nad83 to long/lat WGS84
using m.proj of GRASS GIS.

Output from predict.cgi:
        GMT            Satellite  Satellite  Viewing  Solar   Relative  Scat ang  Glint    Satellite  Satellite  Dist to    MODIS      MOPITT    MISR      ASTER   
year mo da hr mn sc    azimuth    elevation  zenith   zenith  azimuth   (bk=180)  prob(%)  heading    direction  site (km)  (1165 km)  (320 km)  (180 km)  (30 km) 

1987 10 14 15 20 47    283.75     85.18      4.82     49.60   137.01    126.80     2.45    193.33     descend    53.66      +          +         +         -     
2000  3 31 15 45 54    283.76     84.28      5.72     37.76   143.63    137.53    14.50    193.26     descend    63.72      +          +         +         -     
2002  5 24 15 42  9    283.17     84.06      5.94     24.48   162.10    149.82    53.75    193.26     descend    66.22      +          +         +         -     

Comparing these results to the sun azimuth/elevation values in the Landsat metadata files
(2000 and 2002 images), the values computed above are close but some small differences remain.

--------
Analysis prepared in 2016 by

Andrea Balotti, balotti.and AT gmail.com