However, even today, observations still have very limited spatial coverage over the ocean surface.

With two or more satellites, the spatial coverage increases to about 100%.

The addition of the second SSMI satellite drastically increases the spatial coverage to just below 75%.

With three or more satellites, the spatial coverage increases to above 95%.

At the temporal resolution of 6 hourly, the spatial coverage is less than 30% with two or fewer satellites.

With the addition of the TMI, the spatial coverage increases to about 56%.

The addition of the QuikSCAT further increases the spatial coverage to about 66%.

It is difficult to make a precise measurement, due to the difficulty in accurately calibrating the instruments used, and the problem of spatial coverage.

The satellite records have the advantage of greater spatial coverage, whereas the radiosonde record is longer.

Many surveys have a set of parallel traverses and another set perpendicular to it to get good spatial coverage.