Aeronautical cartography

The main purpose of an Aeronautical Chart is to contribute to the safety, regularity and efficiency of International Air Navigation. The increasing speed and operating altitude of modern aeroplanes, coupled with increasing congestion of air traffic necessitate availability of precise and up-to-date charts. This can be achieved by having an efficient system of Aeronautical Chart production.

Aeronautical Charts are primarily meant for the use of Civil and Defence Pilots, Airlines, Air Traffic Controllers, Planning & Engineering, Communication officials, Search & Rescue Personnel, Fire Section, Meteorological and various other organizations. International Civil Aviation Organisation (ICAO) is the prime agency for regulating the design and production of aeronautical charts and the Standards and Recommended Practices and guidelines in this regard are issued by ICAO vide Annex-4 and Doc 8697 (Aeronautical Chart Manual).

Production of charts is a complex and lengthy process, as it involves not only designing, drawing or tracing the charts, but may require the collection of basic field survey data of the area.

In India, Survey and Cartography Unit of Airports Authority of India (AAI), New Delhi has mandate to survey civil aerodromes and other areas for production of Aeronautical Charts. AAI is responsible for surveying and producing aeronautical charts for all the civil airports in the country belonging to AAI, and even for certain other airports as per requirement.

In some other countries, besides the Government Organisations, the job is also done by private agencies. For example m/s Jeppesen of Germany is producing aeronautical charts for sale to pilots and airlines. The major difference in production of charts by Jeppesen is that they do not conduct the field survey to collect the data, but gather the information from various authentic sources. On the other hand, AAI collects the field data also through its own sources.

The aeronautical charts produced by AAI are mainly based on the Standards and Recommended Practices of ICAO. However certain non-ICAO Charts are also produced to meet internal requirements. Among ICAO Charts again there are three categories i.e. Mandatory ICAO Charts, Conditionally required ICAO Charts and Non-mandatory ICAO Charts.

ICAO charts

a. ICAO Mandatory Charts

The following charts have been declared mandatory by ICAO and therefore, they are produced by AAI for publication and sale to various
airlines and other agencies;

Aerodrome Obstacle Chart Type ‘A’ – It shows the obstacles within the approach funnel of the landing and take-off paths of airports and it provides necessary operational data. Pilots take necessary precautions
to avoid those obstacles.

Precision Approach Terrain Chart – It provides detailed terrain profile information within a defined portion of final approach of the aircraft landing at an airport.

Enroute Chart – Provides information to flight crew to facilitate navigation along air traffic services routes. Thus the pilots flying on those air-routes can use the charts for a safe flight.

Instrument Approach Chart – Provides necessary information for instrument approach procedure. Thus an pilot of an aircraft landing at a particular airport is able to follow the specified proceAVIATION dure meant for bringing the aircraft below a particular height to see the runway and land there.

Aerodrome Chart – Provides essential operational information about an aerodrome.

World Aeronautical Chart – They contain small scale maps (1:1 million)
of a particular area showing various geographical features of the land, hills, roads, lakes, rivers, roads etc. and are meant for en-route flying. These maps are produced, published and sold by Survey of India.

b. ICAO Conditionally required Charts

The following charts are declared as “Conditionally required Charts” by ICAO, which means that they are required only if certain conditions/ circumstances prevail;

Aerodrome Obstacle Chart Type ‘C’ – is required where the obstacle data needed by the operator to develop procedures to comply with the operating limitations of Annex 6, Part I and II, Chapter 5, are not published in the AIP.

Area Chart – It gives the details of Air Traffic Services (ATS) routes and aeronautical facilities within the area control. It is to be made available where the air traffic services routes or position reporting requirements are complex and cannot be adequately shown on the Enroute Chart. Terminal Area Chart — Similar to Area Chart and is used for Terminal Areas.

Standard Instrument Departure Chart – used by flight crew for departures. It must be produced where a standard departure route-instrument has been established and cannot be shown with sufficient clarity on the Area Chart.

Standard Arrival Chart – used by flight crew for arrivals. It is to be made available where a standard arrival route-instrument has been established and cannot be shown with sufficient clarity on the Area Chart.

Visual approach chart – Used for descent of the aircraft. It has to be made available for all aerodrome used by international civil aviation where only limited navigation facilities are available or radio communication facilities are not available or no adequate aeronautical charts of the aerodrome and its surrounding at 1:500 000 or greater scale are available, or where visual approach procedures have been established.

c. ICAO Non-Mandatory Charts

The following charts which (though not treated as mandatory by ICAO) are considered essential for safe aircraft operation and therefore they are also produced by AAI;

Aerodrome Obstacle Chart Type ‘B’ – The Aerodrome Obstacle Chart-ICAO Type B should only be produced in such cases where a need arises for a chart to assist in the determination of critical heights, for example, for circling procedures, or in such procedures for use in the event of an emergency during take-off or landing by the aircraft, and of obstacle clearing and marking criteria. When it is necessary to produce a chart combining the specifications of the Aerodrome Obstacle Chart-ICAO Type A and Type B, the combined chart is to be called Aerodrome Obstacle Chart-ICAO (Comprehensive).

Aerodrome Ground Movement Chart – The Aerodrome Ground Movement Chart – ICAO is a supplementary chart to be used where the detailed information needed for the ground movement of aircraft along taxiways to and from the aircraft stands and the parking and docking of aircraft, cannot be shown with sufficient clarity on the Aerodrome Chart-ICAO.Aircraft Parking and Docking chart – Used for facilitating ground manoeuvres of an aircraft. The Aircraft Parking / Docking Chart-ICAO is also a supplementary chart which should be made available only where, due to the complexity of terminal facilities, the information on the ground movement of aircraft between the taxiways and the aircraft stands and the parking / docking of aircraft cannot be shown with sufficient clarity on the Aerodrome Chart-ICAO or on the Aerodrome Ground Movement-ICAO.

Aeronautical Chart 1:500,000 The Aeronautical Chart-ICAO 1:500 000 and the Aeronautical Navigation Chart-Small Scale should be provided only when operational requirements for visual navigation or chart production considerations indicate a need for these charts either as a substitute for or to supplement the World Aeronautical Chart-ICAO 1:1 000 000.

Plotting Chart-ICAO These charts are a useful adjunct where a need exists for a chart which will provide a means of maintaining a continuous flight record of the aircraft position by various fixAeronautical ing methods and dead-reckoning, and maintain an intended flight path. These charts would be appropriate to major air routes over oceanic areas and sparsely settled areas flown by international commercial air transport.

Non-ICAO charts

There are many charts produced by AAI, which are very useful for specific purposes. However, these charts are normally not required to be published by ICAO and therefore, they are available for internal use only.

Brief descriptions and uses of some such charts are given below:

1. Grid Map — This chart shows the details of Operational areas of the aerodrome including runways, taxiways, apron and operational boundary, navigational aids etc. This is one of the most popular charts, that is being extensively used by Operations, Communications, Engineering, Planning, Security, Search & Rescue wings etc. of AAI and also by DGCA, IA, AI and many other organisations.

2. 30 NM Chart — This chart shows height/elevations of hills and other obstructions within the radius of 30 to 40 NM around an airport.

3. ATS route Map — It shows various ATS routes along with restricted/ prohibited/Danger areas within Indian FIR.

4. Zoning map — Zoning map show details of the airport, City areas, AGA Surfaces, various height zones around an airport. Mostly used for NOC purposes.

5. Various other maps — Additionally, AAI produces a large number of miscellaneous maps required by agencies like Search & Rescue Chart, FIR map, Approach Char, Maps showing location of various aerodromes in India, Magnetic Variation Chart, mosaic map, etc.

Survey requirement

Obstacle and other survey data are required to be collected extensively during field surveys for production of Aeronautical Charts. Keeping in view the above requirement a full-fledged survey section has been functioning in AAI, which is fully equipped with most modern equipments and experienced staff specializing in aeronautical survey.

The AAI Survey Party conducts detailed topographical survey of aerodromes and their environs, and carries out detailed obstruction survey of approach paths of the aeroplanes to pin point various obstacles falling in the area. This includes survey for determining location and elevation of hills, high chimneys, tall buildings, Radio and TV Towers etc., likely to cause obstruction to air traffic and endangerthe safety of aircraft operations.

Accordingly location of various objects along with their elevations (heights above mean sea level) is determined. On the basis of this information, i.e. distance, elevation and bearing with reference to a particular point (or geographical coordinates in terms of latitude, longitude and elevations),
various charts are prepared.

The survey of an airport may include physical measurements (horizontal and vertical) of all the objects located inside its boundary (in x, y, and z axis) and those located in its vicinity. Further along the approach funnels all the objects of vertical significance are also required to be measured up to a distance of 15 Kms in each direction (i.e. 30 Kms in both the directions a single runway). For a large international airport like Mumbai, the Survey area may extend as much as up to 300 Sq Kms, where all the high rise buildings, structures, Radio masts, Towers, Chimneys and other objects are to be surveyed. Even for medium-sized airports like Calicut this area may be as much as 100 Sq Kms.

The survey operation can be treated as the foundation stone as well as the building block for production of the charts. If the survey is incomplete or faulty, the same defects are likely to crop up either locally or even in magnified form during the subsequent process of chart production. Due to this reason, precise and accurate observations are required to be made during survey operation and data so collected is regarded as an important asset.

In addition to the above, the data from other available sources such as Survey of India Maps, State Government, private agencies etc., is also collected and utilised for preparation of these charts.

Use of modern techniques

All possible endeavours are made to produce Aeronautical Charts of high standard that are comparable to charts produced by other advanced countries. Efforts are also made to keep pace with rapid developments in aviation by introducing modern techniques such as use of precision drawing instruments, introduction of digital and electronic survey equipments like Electronic Theodolite, long range Distomats, Geodetic dual frequency Global Positioning System (GPS) etc., and of course by the use of Computers, which are required to be used extensively for production of aeronautical charts.