### ...about the visualization

The Digital Aerontautical Chart Supplement(DACS) is a subset of the positional data used by the Federal Aviation Administration and the National Oceanic and Atomspheric Administration to manage the National Airspace System. DACS is updated every 56 days.

Shown here is a visualization of DACS using data from the Northeast superimposed on the outlines of the states.

The yellow lines represent victor airways. These are flightpaths used by aircraft operating in the IFR system below 18,000 feet above sea level. A pilot must file a flight plan based on these routes (or the on the jet routes for the portion of her flight above 18,000 feet). Just prior to takeoff, she would receive a clearance from air traffic control specifying which of these flightpaths to follow.

You can try zooming into a depiction of the airways and then turning on the display of intersection names. Every intersection is given a 5 letter name. Look for <fixed>BOSOX</fixed> intersection southwest of Boston or <fixed>LBSTA</fixed> which is northeast of Boston. The instrument approach into Pease International in Portsmouth, NH is well known for a sequence of intersection names: <fixed>ITAWT, ITAWA, PUDYE, TAAHT, IDEED</fixed>

> Jet routes are used between 18,000 and 60,000 feet above sea level. If you're above 60,000 feet you're own your own. Just don't forget your oxygen bottle.

> The green balls are airports equipped to provide a surveillance radar approach - a procedure normally used to assist a pilot who has lost navigational capability. The silver balls represent the locations of long range radar facilities. The orange circles are selected airports sized according the length of the longest runway.

### ...about the visual program

This visual program reads connectionless data. Since each data point represents an intersection, consequtive points in the data set are connected using a combination of a special import filter which detects begin and end points of airways, Compute, Mark, and Replace.

### ...about the conversion to web page

The original net has 4 image tools. Three of these tools provide the images you see here. The fourth is routed off unless you select the vrml option in the control panel. The subsequent execution would cause an additional browser window to open showing the vrml world. This doesn't work with Internet Explorer 4.0 or Netscape 4.05.

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