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and off-route VORs are used to establish intersections. NDBs are sometimes collocated with intersections, in which case passage of the NDB would mark the intersection. A bearing to an off-route NDB also can provide intersection identification. A localizer course used to identify an intersection is depicted by a feathered arrowhead symbol on the en route chart ( ). If feathered markings appear on the left-hand side of the arrowhead ( ), a back course (BC) signal is transmitted. On AeroNav Products en route charts, the localizer symbol is only depicted to identify an intersection. 

Off-route VORs remain the most common means of identifying intersections when traveling on an airway. Arrows depicted next to the intersection  indicate the NAVAID to be used for identification. Another means of identifying an intersection is with the use of DME. A hollow arrowhead indicates DME is authorized for intersection identification. If the DME mileage at the intersection is a cumulative distance of route segments, the mileage is totaled and indicated by a D-shaped symbol with a mileage number inside . [Figure 1-4]  Approved IFR global positioning system (GPS) units can also be used to report intersections. 

## Other Route Information 

DME and GPS provide valuable route information concerning such factors as mileage, position, and ground speed. Even without this equipment, information is provided on the charts for making the necessary calculations using time and distance. The en route chart depicts point-to-point distances on the airway system. Distances from VOR to VOR are charted with a number inside of a box . To differentiate distances when two airways coincide, the word “TO” with the three-letter VOR identifier appear to the left of the distance boxes . 

VOR changeover points (COPs) are depicted on the charts by this symbol . The numbers indicate the distance at which to change the VOR frequency. The frequency change might be required due to signal reception or conflicting frequencies. If a COP does not appear on an airway, the frequency should be changed midway between the facilities. A COP at an intersection may indicate a course change. 

Occasionally an “x” appears at a separated segment of an airway that is not an intersection. The “x” is a mileage breakdown or computer navigation fix and may indicate a course change. 

Today’s computerized system of ATC has greatly reduced the need for holding en route. However, published holding 

patterns are still found on charts at junctures where ATC has deemed it necessary to enable traffic flow. When a holding pattern is charted, 

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the controller may provide the holding direction and the statement “as published.” [Figure 1-4] 

Boundaries separating the jurisdiction of Air Route Traffic Control Centers (ARTCC) are depicted on charts with blue serrations . The name of the controlling 

facility is printed on the corresponding side of the division line. ARTCC remote sites are depicted as blue serrated boxes and contain 

the center name, sector name, and the sector frequency. [Figure 1-4] 

## Weather Information and Communication Features 

En route NAVAIDs also provide weather information and serve communication functions. When a NAVAID is shown 

as a shadowed box, an automated flight service station (AFSS) of the same name is directly associated with the facility. If an AFSS is located without an associated NAVAID, the 

shadowed box is smaller and contains only the name and identifier. The AFSS frequencies are provided above the 

box. (Frequencies 122.2 and 255.4, and emergency frequencies 121.5 and 243.0 are not listed.) 

A Remote Communications Outlet (RCO) associated with a NAVAID is designated by a thin-lined box with the 

controlling AFSS frequency above the box and the name under the box. Without an associated facility, the thin-lined RCO box contains the AFSS name and remote frequency. 

## Automated Surface Observing 

Station (ASOS), Automated Weather Observing Station (AWOS), Hazardous Inflight Weather Advisory Service (HIWAS), and Transcribed Weather Broadcast (TWEB) 

are continuously transmitted over selected NAVAIDs and depicted in the NAVAID box. ASOS/ AWOS are depicted by a white 

“A”, HIWAS by a “H” and TWEB broadcasts by a “T” in a solid black circle in the upper right or left corner. 

## New Technologies 

Technological advances have made multifunction displays and moving maps more common in newer aircraft. Even older aircraft are being retrofitted to include “glass” in the flight deck.  [Figure 1-6]  Moving maps improve pilot situational awareness (SA) by providing a picture of aircraft location in relation to NAVAIDS, waypoints, airspace, terrain, and 

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