Home' RTCA Documents for Review : DO-201B User Requirements for Navigation Data Contents ED-77A/DO-201BforOpenConsultation/FRAC
© EUROCAE, 2018
of the value to be achieved dictates the amount of precision needed in the survey or
data acquisition method. It is important that this acknowledgement of the existence of
unknown defects does not create an error budget for data chain participants. In addition,
once defects are identified they are removed from the navigation data even if the
existence of those errors are consistent with statistical models.
Some navigation data elements are not published by Aeronautical Information Services,
but calculated by Data Service Providers based on published values. End user
requirements on accuracy may apply to these calculated parameters also, and evidence
of compliance can be demonstrated based on the accuracy of data used in the
Navigation data needs to have sufficient resolution to maintain accuracy. If an accuracy
of 0.1 units is needed, then a resolution of .001 units would enable a data chain to
preserve the accuracy without issue. Resolution throughout the data chain is often
impacted by the interchange formats used. A data chain participant could store data
with less resolution if the resulting data and all computed values based on this data still
comply with the accuracy requirements of the user.
This document does not describe a format for navigation data to be exchanged. At the
time of publishing of this document, much of authoritative source data is still provided in
either paper or electronic equivalents of paper not well suited for machine parsing or
downstream users. The data is therefore translated multiple times throughout the data
chain, with each participant using a format suited to their needs. Upstream formats
typically differ from downstream formats in encoding, style, and intended use (e.g.,
upstream members of the data chain may use Aeronautical Information Exchange
Model (AIXM), and the downstream members may use ARINC 424). Translating format
per the processing requirements in DO-200B/EUROCAE 76A is acceptable.
Completeness reflects the degree of conformance of a navigation database in relation
to the expected content as specified by the user data quality requirements.
Completeness depends on the declared needs of which data elements, metadata, etc.
must be included in the database. Completeness to meet the intended function of an
application is applied to the coverage needs of an operator (e.g., an operator may apply
regionalization that reduces the geographic scope of the database without affecting the
The data requirements specified in this document are based on the anticipated needs
of the intended applications described in Appendix A. Only a complete set of navigation
data can ensure that system designers can implement all of the envisioned applications.
However, not all applications require a complete set of navigation data to enable their
intended use. For example, a runway safety application does not require navaid data.
Navigation data is categorized by 3 assurance levels: Critical (1), Essential (2), and
Routine (3) (see DO-200B/ED-76A Appendix B.1.3).
To maintain data integrity and comply with industry requirements in this document, data
originators should [NAV-D001] provide any data that is assurance level 1 in a digital
form with digital error detection mechanisms, preferably Cyclic Redundancy Checks
(CRC). This enables data chain participants to use the data by checking the digital error
detection, import the data with qualified tools, and/or other techniques described in DO-
200B/ED-76A Appendix C.2 . Source data that does not support use of computer
algorithms cannot be used to claim compliance to this standard for assurance level 1.
Assurance level 2 and 3 data often drives the use of manual processes. This is the state
of practice, however if source was in a digital form it could reduce workload on data
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