NavData Chart Compatibility

Jeppesen Airway Manual Charts are the same publications that Jeppesen has provided to the aviation community for many years. NavData has not been around for quite as long, but has established and maintained the same reputation for accuracy, reliability, and dependability with those customers who use computerized navigational systems and other computer navigation data bases from Jeppesen. For those who subscribe to both services, slight differences may occasionally be noted between what is seen on the chart and what is generated from the navigation database. Any or all of the following may cause these differences:

1. Differences in Publication Criteria
Our computerized NavData is updated and issued every 28 days. This is a relatively quick and simple operation for the user, since all of the changes are included on the updated media that is loaded into the aircraft navigation system or a mainframe computer system. The charts are quite a different story, as each chart must be individually updated and published. The new charts are then collated and mailed, and once received by the customer, must be filed individually in the Airway Manual. Variations, such as differences in information cut-off dates and lead-time requirements, may bring about distribution in one medium before the other. These differences are generally resolved in the NavData NOTAMs and the Jeppesen Chart NOTAMs. The NOTAMs provide a weekly or bi-weekly update to the NavData and Chart services. A review of the Jeppesen NOTAM pages prior to using either service will help to ensure that you have the most current information.

2. Differences in the Method Used to Determine Bearing and Distance Values on Charts and in Computerized Navigational Systems
Bearings and distances on airways, approach transitions, and instrument approaches are published in a country's Aeronautical Information Publication (AIP). Almost exclusively, these values are taken from the AIP and published on Jeppesen charts. In contrast, the navigation database contains exact locations of the navaids used to form tracks of airways, approach transitions, and instrument approaches. System software computes great circle route bearings and distances based on the most current navaid information on the desired route, and presents this data on the system display. Slight differences in bearing and distance may not be changed in the AIP, and therefore, may not change on the our charts. But if navaid information has changed even minutely, differences may show up because the bearings and distances displayed are computed by the navigation system or computer flight planning software each time a particular track is called up.

3. Differences in Waypoint Names and Coordinates
Waypoint names published on our charts are taken directly from official government sources. In some countries, there are no restrictions on the number of characters used in the name. Computerized navigation system software limits waypoint names to a maximum of five characters. Therefore, waypoint names with more than five characters will be abbreviated for entry into the navigation database. Jeppesen has included an explanation of the method used to abbreviate these names on NavData pages 5 through 10, titled "NavData Name Conventions". Note that the basic structure of the name is retained, and it should be relatively easy to tie that abbreviation generated by the database to the complete name of the waypoint on the chart. In addition, there are unnamed turning points and intersections depicted on charts that must be included in the navigation database. Therefore, certain names may appear in a computerized system that do not appear on a chart. The method used to identify these turning points and intersections is also included in "NavData Name Conventions."