Maps GPS Glossary - T
talus - Rock debris at the base of a mountain or cliff.
tank - A usually artificial pool, pond, reservoir, or cistern, especiallly one used to hold water for drinking or for irrigation.
tarn - A small mountain lake, especially one formed by glaciers.
thalweg - The deepest line that can be found along a river bed or valley.
theodolite - An optical instrument consisting of a small mounted telescope rotatable in horizontal and vertical planes, used to measure angles in surveying, meteorology, and navigation.
TIGER - Topologically Integrated Geographic Encoding & Referencing - A U.S. Census Bureau mapping system.
time to first fix - See TTFF.
time zone - A region that has uniform and legally mandated standard time. There are 40 time zones on land.
TOPEX - TOPography EXperiment for Ocean Circulation; unflown NASA precursor mission to TOPEX/Poseidon.
topography - The graphic representation of the landform on a map by the use of contour lines.
toponomy - The scientific study of the different names the places have, their meaning and origins.
township - A unit of survey of the public lands of the United States, normally a quadrangle approximately 6 miles on a side with boundaries conforming to meridians and parallels within established limits, containing 36 sections.
track - A collection of points that show the path travelled.
track point - A single point on the path travelled.
track up orientation - This setting allows a GPS receiver user to set it so that the current track heading will always be located at the top of the screen.
traffic message channel (TMC) - Technology that offers drivers updates regarding traffic and travel delays.
transit - A precision surveying instrument; a theodolite in which the telescope can be reversed in direction by rotation about its horizontal axis.
triangulation - The method of determining a location on a map by using two or more points through which lines of known directions are drawn; the intersection of these lines is the desired location; can use distance and/or angles.
trilateration - The same method as triangulation, except trilateration uses only distances for locating.
Tropic of Cancer - Circle of latitude that marks the northern boundary of the tropics.
Tropic of Capricorn - Circle of latitude that marks the southern boundary of the tropics.
troposphere - The portion of the atmosphere from the earth's surface to the stratosphere.
true north - The geographical north pole.
TTFF - Time To First Fix - The time it takes for a GPS receiver to lock onto the satellite signals and determine the initial position.