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The process of interpreting reported information on movements of aircraft, ships, and submarines in order to determine their probable true tracks and, where applicable, heights or depths.


(1) See packet filter and filter bubble.

(2) To select data. Filters use patterns (masks) against which all data are compared and only matching data are "passed through," hence the concept of a filter. For example, email clients and servers can look for messages with text patterns that are recognized as spam and delete them. An email client can be set up to filter messages and store them in separate mailboxes as a way of organizing the mail, or it can be set to alert the user when a certain type of message arrives. See Bayesian filtering, spam filter and algorithmic filter.

(3) To change data. In this usage of the term, the concept of a filter (pass-through device) is less obvious, but nevertheless widely used. For example, a sort routine changes the sequence of data. A conversion routine (import or export filter) changes one type of data, text or graphics format into another. See image filter and parse.
References in periodicals archive ?
Consequently, the pass-band bandwidth is also reduced by the same factor, and filtering is performed with non-recursive filters, without sample rate conversions, and without feedback loops.
This paper proposes a simple areal filtering algorithm based on the high-order spline filter.
The Donaldson filter is rated to last 500 hours and while the synthetic filtering media isn't governed by the air filter AD, it still must be replaced at 500-hour intervals, after three years or after five cleanings--whichever comes first.
Conical shaped brew chambers are fitted with creped paper filters while cylindrical filtering chambers accept cup-cake shaped fluted filters made from smoother surface filter paper.
However, he says, because the pore sizes in his team's membrane are more uniform than those in conventional membranes, a carbon-nanotube filter could be especially effective at filtering out selected chemicals or microorganisms.
To stop spam and viruses from entering the system in the first place, and to ease the concern of keeping spam filters current, many businesses turn to remote e-mail filtering services that can pre-process e-mail before it is delivered to the company.
A BPL spokeswoman says the library's board of directors would soon decide on what kind of Web filtering solution to use at the system's 60 locations.
But the conclusion seems foregone: The city already has taken a stand against such filtering programs.
Chapter 14 is an introduction to switched capacitor filters, while Chapter 15 outlines the process of digital filtering. Chapters 16 and 17 are dedicated to digital filtering in a little more depth--Chapter 16 covers FIR filters and Chapter 17, IIR filters.
And according to a recent New York Times editorial, filtering software "overblocks" by 15 percent or more.
Believing that the job of protecting students from Internet dangers has been done by installing filtering software at school is a prescription for more incidents such as this.
They don't do a particularly good job of filtering out ultra-fine dust because the paper filter is too porous.