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.
sea level - The measurement of the average height of the oceanís surface.
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.
sextant - Instrument used in measuring the distances between any two objects, like a celestial object and the horizon.
shoreline - The stands between a body of water and a land area on a map.
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.
soap hole - A hole resulting from the wetting of the outcrop surface of bentonite.
SOG - see Speed Over Ground
soil map - The type of map that shows the distribution of soil types and/or properties in different areas.
sound - A long, relatively wide body of water, larger than a strait or a channel, connecting larger bodies of water.
South Pole - The surface located in the southern hemisphere where the Earth's axis of rotation meets its surface. It is also known as Antarctica.
Space Based Augmentation System - See SBAS.
space segment - The part of a GPS system that is located in space.
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.
stereoplotter - A device that uses stereo photographs in order to determine elevations. It has been used since 1930 to plot contour lines on topographic maps.
straight-line navigation - Travelling the distance between two waypoints in the most direct line possible.
strath - A wide river valley.
stratosphere - The region of the atmosphere above the troposphere and below the mesosphere.
subsidence - The movement of an area due to tectonic, seismic, or artificial forces that triggers a decrease in elevation.
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.
symbol - Simple drawing, letter, shortened word or colored shape used on a map to represent a real object.
syke - See sike.