Tip: to find a specific term, use the Acrobat search : click D on the binocular icon in the window bar menu
Dialogue For the purposes of PETAL, the term ‘dialogue’ refers to the human dialogue or, for example, that period from controller HMI input of a message to the time the controller sees the aircrew acknowledgement to that message displayed on his screen. Dialogue Request A Dialogue Request is the stating point of a dialogue. It conveys a request, an instruction or some specific information to be treated and responded upon by the receiving system or operator. The Dialogue Request can be human or system generated. A Dialogue Request may be followed by one Logical Response and/or one Operational Response. Difference Pattern The receiver (1090 MHz) characteristic of a monopulse SSR antenna, obtained by connecting together in anti phase the signals (replies) received by two partial antennas. The difference pattern has a minimum in the main radiation direction of the antenna, and an amplitude and phase characteristic which varies as a function of angle of arrival of the received signal. Used in conjunction with the sum output of the antenna, it enables the off bore sight angle to be found. Differential Global Navigation Satellite System Is an augmentation, the purpose of which is to determine position errors at one or more known locations and subsequently transmit derived information to other GNSS receivers in order to enhance the accuracy of the position estimate Differential Global Positioning System A technique for improving GPS solution accuracy. Error is reduced by determining the error at a known location, then subtracting that error from the solution at an unknown location. Digital Data Data in the form of digits or integral quantities. Contrast with analogue data. Digital Signal Processor A computer oriented toward math-intensive applications, often a single chip or small chip set. Dilution of Precision A numerical value expressing the confidence factor of the position solution based on current satellite geometry. The lower the value, the greater the confidence in the solution. DOP can be expressed in the following forms. GDOP - all parameters are uncertain (latitude, longitude, height, clock offset); PDOP - 3D parameters are uncertain (latitude, longitude, height); HTDOP - 2D parameters and time are uncertain (latitude, longitude, time); HDOP - 2D parameters are uncertain (latitude, longitude); VDOP - height is uncertain; TDOP - clock offset is uncertain. Direct Controller Pilot Communication A method of radio communication between air traffic control and the cockpit which features instantaneous voice responses, by either party, allowing the use of reduced separation criteria. Direct Support Tasks Tasks which contribute to the design and provision of the product and/or service in the short term. Direction Finding Displays the bearing of a transmitting aircraft Equipment DIF from the airport. Disabled Person Somebody with a physical or mental impairment that substantially limits one or more major life activities (Americans with Disabilities Act ADA, 1990). Discovery Computer Based Training Interactive discovery learning making use of a multimedia computer.