GIS Dictionary | Letter T

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– T –

A spatial dataset containing a common feature type. Themes are also referred to as layers or coverages.

A numerical value representing the acceptable error range a feature will have from its actual point found on earth.

Topology stores the relationships of one spatial element with respect to another

Transactional Geography (Definition provided by Di-Ann Eisnor of Platial)
Transactional cartography is the movement from mapproviding entertainment/information to map as enabling action. This shift in mapmaking is possible due to the merging of crowd-sourced information and access to real time data. Both bring location to vast amounts of complex data and allow for new forms of analysis and visualization. In the past we emphasized mapping (relatively) static objects like rivers and roads, it evolved to mapping people and their movements and now continues to accelerate to mapping complex processes. Transactional cartography and the utilization of these new sources and abundance of data can actually impact decisions and actions such as a when/where to purchase a product, when/where and with whom to barter, when/where most effective routes for emergency response, when/where to build new roads or public facilities, when/where to buy a home, change a route or itinerary based on real-time circumstances and real world situation. In this realm, time is inextricably linked to location which removes historic obstacles to actionable or live mapping.

Triangulated Irregular Network (TIN)
A surface representation derived from irregularly spaced points and breakline features. Each sample point has an x, y coordinate and a z value or surface value.

Triangulation Station
A point on the Earth, the position of which is determined by triangulation. Also called trig point.

Triangulation Station in the Santa Monica Mountains, California.
Triangulation Station in the Santa Monica Mountains, California.

GIS Acronyms that start with T

TEC – Topographic Engineering Center, U.S. Army Corp of Engineers


TIFF – Tagged Image File Format

TIN – Triangular Irregular Networks

More geographic concepts from the GIS dictionary:

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GIS Dictionary | Letter S

GIS Dictionary | Letter U