~ Captain Paul's response to: ~ Rick Lemoine ~

The Captain Paul’s Fishing Edge of GPS Waypoints for the Vermillion bay includes EDGE sites from Point Chevreuil and East Cote Blanche Bay reefs at the Gulf on the East, to the junction of the Intra Coastal Water Way (ICWW)and The Freshwater canal on the west of the areas from the Gulf of Mexico to the ICWW.

It includes locations in Vermillion Bay, Little White Lake, Belle Isle Lake, the Weeks Bay area, The Cypremort Point area, the South West Pass area of Vermillion Bay, Tete Butte and Diamond Reef areas, and numerous points in and around Marsh Island.

The Vermillion EDGE contains over 200 waypoints that are throughout this area. The Lake Calcasieu (Big Lake) EDGE has 140 waypoints. Both are only available on the LOUISIANA SPORTSMAN WEB SITE’s OUTDOOR STORE.

~ Captain Paul ~

~ Captain Paul's response to: ~ NandDakyaw ~

I am not sure exactly what you are asking about, but I do have some information on SELECTIVE AVAILABILITY in the GPS system.

SELECTIVE AVAILABILITY was a term used to describe an intentional degrading of the GPS signals which caused the civilian version of GPS, to provide an accuracy of about 100 meters (320 feet).

The U.S. Department of Defense designed, operates and maintains the Global Positioning System. The system consists of 24 satellites active satellites with several satellites in orbit as spares. There are at least four satellites visible from any location on the surface of the earth at any time. These satellites broadcast a timed signal that is accurate to 1/40,000,000,000 of a second.

Your GPS receiver interprets the signals and using internal software programs determines a position by triangulating the time that the signals take to reach the GPS receiver from four or more of these satellite transmissions. It measures the time that the signals take in route to the GPS receiver. These signals travel at the speed of light, which is about 186,282 miles per second. The more satellite signals that are received allow for a more accurate computation of the position on the earth.

The GPS constellation when used by the military and the Military Defense Mapping can discern a position to with a few centi-meters. These signals are transmitted as a similar but different frequency than the civilian versions of the GPS. At first the Defense Department did not want non-U.S. Military applications to have the super accurate determination of earth positions. So, a system was designed to INTENTIONALLY degrading the GPS civilian satellite signals.

GPS includes a (currently disabled) feature called Selective Availability (SA) that adds intentional, time varying errors of up to 100 meters (328 ft) to the publicly available navigation signals. This was intended to deny an enemy the use of civilian GPS receivers for precision weapon guidance.

This Selective Availability degradation was eliminated May of 2000.

In making the announcement, the President stated, “New technologies demonstrated by the Department of Defense enable the United States to degrade the GPS signal on a regional basis. Should a National Security issue arise, SA signals could be placed in a specific region. This region-specific action would NOT affect other worldwide users.”

However, it is possible, if the Department of Defense believes that a hostile group may use the GPS system to cause an attack on the U.S., that SA will again be activated. In the event that SA is activated, worst-case accuracy would go from under 20 meters as it is now the standard to 100 meters in all GPS civilian receivers as when SA was active.



But in the meantime the Federal Aviation Administration (FAA) designed and placed in orbit satellites that broadcast a CORRECTED GPS signal, that is called Wide Area Augmentation System (WAAS). The WAAS satellites are geostationary, in that they are above the same location of the earth all of the time. WAAS satellites broadcast within the range of the standard GPS satellites, making it available to any standard civilian GPS unit that includes the WAAS radio feature. This is a common feature on most modern GPS units.

It is designed to assist commercial airline pilots in landings at commercial airports.

Using the GPS satellites and the WAAS feature, modern GPS units can discern a position to within 3 meters, about 9.8 feet and offers the casual GPS user an extreamly accurate navigation tool.

It is possible, if the Department of Defense believes that a hostile group may use the GPS system to cause an attack on the U.S., that SA or a version thereof, will again be activated. But, newer technology since 1992 when the GPS~ Selective Availability was designed, can allow the Department of Defense to disable or distort the signals for a very precise area. This can allow civilian units to be less accurate in certain areas if there is a national security issue in that area.

This capability of distorting the GPS signals has NOT occurred during the latest mid-east military action in Iraq and Afghanistan.

Selective Availability should NOT be a concern to any person who may want to use a GPS. As said, a modern unit can with GPS and WAAS determine a very, very accurate position that was unheard of just a few short years ago.

~ Captain Paul ~