|Points scan in +i direction| |Points scan in -i direction|
|Points scan in -j direction| |Points scan in +j direction|
|Adjacent points in i direction are consecutive| |Adjacent
points in j direction are consecutive| |reserved; set = 0| i
direction is defined as west to east along a parallel of
latitude, or left to right along an x axis. j direction is
defined as south to north along a meridian of longitude, or
bottom to top along a y axis.