VisualGPS (Freeware) incorporates many advanced features found in professional programs. Its sole purpose is to display graphically specific NMEA 0183 sentences and show the effects of selective availability (SA).
VisualGPS is a general purpose utility for monitoring the output of a GPS receiver. Using the NMEA data from the GPS receiver, VisualGPS will display various statuses graphically. Tools such as a survey utility average the position and shows accuracy of the GPS receiver in a static application.

VisualGPS Features:
1. Azimuth and Elevation Graph - View all satellites that are in view. Each satellite identifies its pseudo random number (PRN) and its azimuth and elevation. Also plot and print the physical mask angle.
2. Survey - The survey window displays both position and xDOP (HDOP and VDOP) parameters. The ability for user selectable HDOP/VDOP color thresholds for position averaging make a great utility. Also monitor Standard Deviation and effects of Selective Availability. That's not all - print the results graphically. (Click here for example print output) (in PDF format - 157K)
3. Signal Quality/SNR Window - Monitor satellite signal to noise ratios and see them graphically on the screen. The signal quality window will grow or shrink to accommodate number of satellites in view
4. Navigation - Monitor latitude, longitude and altitude
5. NMEA Command Monitor - View NMEA sentences as they are received

The license of this software is Freeware, you can free download and free use this wireless communication software.