Maps GPS Glossary - S

S/A - See selective availability.

saddle - A dip along the top of a ridge.

SBAS - Space Based Augmentation System - Any system that uses a network of geostationary satellites and ground stations to enhance the performance of a Global Navigation Satellite System (GNSS) by providing signal corrections and additional satellites with known and constant positions.

scale - The distance on a map that corresponds to the same points on the earth.

SD - See secure digital.

second - A unit of measurement; one minute contains 60 seconds; one degree contains 3600 seconds.

secular variation - Complex fluid motion in the outer core of the Earth that causes the magnetic field to change slowly with time.

secure digital - A type of technology for mass storage devices in the form of a type of memory media with a compact design and is compatable with different digital camera brands and MP3 devices.

selective availability - S/A - The intentional degradation of GPS accuracy for civilian use (S/A has been deactivated indefinitely as of May 2, 2000). S/A limited the accuracy of civilian GPS systems to 300 feet or less 95% of the time.

SEP - Spherical Error Probable - The radius of a sphere within which there is a 50 percent probability of locating a point or being located.

SET - Surface Elevation Table - A portable mechanical leveling device for measuring the relative elevation of wetland sediments.

sike - A small stream.

siphon - A pipe connecting two canals.

sleeve - An attachment for a PDA which allows you to use items like network or modem cards, PCMCIA or CF cards, digital cameras, a GPS/GPRS phone, or an extra battery pack with a PDA.

slough - 1) A depression or hollow, usually filled with deep mud or mire. 2) A stagnant swamp, marsh, bog, or pond, especially as part of a bayou, inlet, or backwater.

SMG - Speed Made Good - Required speed to destination given the current course.

SMS - Short Message Service (also called text messaging) - A function available on digital GSM networks allowing text messages to be sent and received via the network operator to a mobile phone, or from the Internet, using an "SMS gateway" website.

SOG - see Speed Over Ground

sound - A long, relatively wide body of water, larger than a strait or a channel, connecting larger bodies of water.

Space Based Augmentation System - See SBAS.

Speed Over Ground - The speed at which the GPS unit and the person operating it are moving with respect to the earth's surface (ignoring tidal and current activity).

Spherical Error Probable - See SEP.

spheroid - A body that is shaped like a sphere but is not perfectly round.

SPS - The normal civilian positioning accuracy obtained by using the single frequency C/A code.

spur - A small ridge.

statute mile - A unit of length equal to 5280 feet (1609 meters).

steppe - A vast semi-arrid grassy plain.

strath - A wide river valley.

stratosphere - The region of the atmosphere above the troposphere and below the mesosphere.

Surface Elevation Table - See SET.

SVG - Scalable Vector Graphics - An XML markup language for describing two-dimensional vector graphics, both static and animated. It is an open standard created by the World Wide Web Consortium, which is also responsible for standards like HTML and XHTML.

swale - 1. A low tract of land, especially when moist or marshy. 2. A long, narrow usually shallow trough between ridges on a beach, running parallel to the coastline. 3. A shallow troughlike depression that carries water mainly during rainstorms or snow melts.

syke - See sike.