The difference in UTC between consecutive table rows gives the step size time interval of the calculation. Each row represents the position of the satellite at a specific instant in the satellite's orbital path. In the case of the sample ephemeris table above the step size time interval is one minute. WMD represents Westminster, Mayrland. Depending on the range of the satellite, the predictions may or may not be valid for other stations at scattered locations.
Most satellelite predictions are good for several tens of miles away from the designated station.
Azimuth and Altitude Specifies a point in the sky relative to the horizon and the cardinal directions. Azimuth , as shown in the illustration at left, measures the position of an object around the horizon of the observer. Azimuth is given in degrees and ranges from 0.0 to 359.9999 in the table. Azimuth 0.0 is due North and values increase toward the east. Altitude specifies an angular distance above the horizon given in degrees.