What is Parallax?
Parallax is the apparent difference in the location of an object based on point of view. With satellite data this is always something important to consider, because the features you see may not actually be where they appear. This is the first of a three part series focused on the parallax problem. This introduction will review orbital characteristics of the two most common types of meteorological satellites with very different parallax issues. The next two parts will describe those issues in greater detail.
Satellites and Their Types
Polar satellites orbit over the poles at a substantially lower altitude, around 850 miles, and at a much faster speed. It takes around 90 minutes for a polar satellite to complete one full orbit around the earth. As the earth turns below it, the swath of each pass covers an area just to the west of the previous pass. There is usually some overlap with successive passes that is dependent on latitude and the width of the swath. Polar regions have more frequent overlapping coverage since the orbital tracks always pass near the poles.
So, both types of satellites have some amount of parallax displacement in locations where their viewing angles are large, which is a function of their orbit. The next two parts will focus on each of these types in greater detail.
By Carl Dierking