ICAO PANS-AIM (Doc 10066) and eTOD: Obstacle Data Accuracy by Area

Under eTOD, EASA’s guidance asks 0.5 m horizontal and 0.5 m vertical accuracy for obstacles in Area 3, 5 m and 3 m in Area 2, 2.5 m and 1 m in Area 4, and 50 m and 30 m in Area 1, all at 90 percent confidence. ICAO’s PANS-AIM tables are paywalled and were not read.

Electronic terrain and obstacle data, eTOD, is the name for the digital records of obstacles and terrain and for the rules on how good they must be. Annex 14 points to PANS-AIM for the accuracy and integrity classes. The numbers below come from EASA’s free guidance to Regulation (EU) No 139/2014 and from Annex 14, and each is tied to the page it was read on. For a practical reading for an operator, see our post on what accuracy obstacle data has to meet .

What binds and what only guides

Start with ICAO. Annex 14 Volume I, 9th edition, 2.1.1 says the determination and reporting of aerodrome-related aeronautical data “shall be in accordance with the accuracy and integrity classification required to meet the needs of the end-users of aeronautical data.” The Note under it says those specifications are in PANS-AIM (Doc 10066), Appendix 1. Paragraph 2.5.5 is the obstacle one, and its Note says Appendix 8 of Doc 10066 “provides requirements for obstacle data determination in Areas 2 and 3.” Both paragraphs are Standards. The Notes are not. The Foreword describes Notes as giving “factual information or references” and “not constituting part of the Standards or Recommended Practices.” So Annex 14 requires data to meet its end-users’ needs, and leaves the numbers to a separate ICAO document. Annex 14’s amendment record lists, under Amendment 14 (8th edition), a consequential amendment for the restructuring of Annex 15 and the introduction of PANS-AIM, covering the change of references, the data quality requirements and the data error detection requirements.

The EU route is different. Regulation (EU) No 139/2014 ADR.OPS.A.005 says the aerodrome operator shall, as appropriate, determine, document and maintain data relevant to the aerodrome and to provide it to users, air traffic services and aeronautical information services providers. ADR.OPS.A.010(b) says the accuracy of aeronautical data must be as specified in the aeronautical data catalogue. ADR.OPS.A.030 says that when the operator originates, processes or transmits data to the AIS provider, the data in Appendix 1 to Annex III of Implementing Regulation (EU) 2017/373 must conform to the catalogue specifications. The area definitions and Tables 1 and 2 sit in GM4 to ADR.OPS.A.005(a). EASA’s own terminology defines guidance material as “non-binding material” that helps to illustrate a requirement.

That leaves a plain statement of status. The Annex 14 sentences are ICAO Standards. Doc 10066 is a separate ICAO document that Annex 14 mentions only in Notes. The EASA tables are guidance, and the binding EU duty is to meet the data catalogue. This page quotes the EASA tables because they are the numbers a reader can check for free.

Older material still cites Regulation (EU) No 73/2010 for data quality. Article 4 of Implementing Regulation (EU) 2020/469 repeals it with effect from 27 January 2022. Sweden’s implementation plan records the same in a footnote and adds that its content is carried in Regulations 2017/373 and 139/2014.

The four coverage areas

GM4 to ADR.OPS.A.005(a), on pages 261 to 267 of the March 2026 Easy Access Rules, defines the areas. The values below are read from that text.

Areas 2a to 2d and Area 3 are built from familiar parts of an aerodrome. The runway strip , the clearway and the movement area set their inner edges, and the aerodrome reference point anchors the 45 km limit.

Which obstacles get collected

Collection is not “everything in the area.” Each area has a collection surface or a height threshold, and only what rises through it is in scope. GM4 sets them out.

In Area 1, data on every obstacle 100 m or higher above the ground should be collected and recorded. In Area 2, the Area 2a surface is 3 m above the nearest runway elevation along the centre line, and at the elevation of the nearest runway end for clearway portions. The Area 2b and 2c surfaces slope at 1.2 per cent. The Area 2d surface is 100 m above ground. Under AIS.TR.360(c) of Regulation (EU) 2017/373, obstacles less than 3 m high in Area 2b and less than 15 m high in Area 2c need not be collected. In Area 3, the surface is 0.5 m above the horizontal plane through the nearest point on the movement area. For Area 4, more detailed obstacle data may be collected to the Area 4 column of Table 2.

AMC1 ADR.OPS.A.005 then says what the operator should provide. Electronic obstacle data for all obstacles in Area 2 within the aerodrome boundary that are assessed as a hazard to air navigation. Electronic terrain and obstacle data for Area 2a that penetrate the collection surface, for penetrations of the take-off flight path area obstacle identification surfaces, and for penetrations of the aerodrome obstacle limitation surfaces . For Area 4, data where CAT II or III operations are established and operators need detailed terrain information to assess the effect of terrain on decision height determined by radio altimeter. These are AMC, so each says “should.”

Obstacle data numerical requirements

Table 2 in GM4 is the one readers ask for. Table 1, for terrain, repeats the same figures and adds a post spacing row of 3, 1, 0.6 and 0.3 arc seconds, which is about 90 m, 30 m, 20 m and 9 m. Table 1 starts on page 266 and Table 2 is on page 267. Both were checked against the rendered pages, not only the extracted text.

Three things are worth reading out of it.

Accuracy tightens from Area 1 to Area 3. Area 4 sits between Area 2 and Area 3 on both axes, at 2.5 m horizontal and 1 m vertical.

Resolution is not accuracy. GM1 to ADR.OPS.A.010(d) says resolution must be commensurate with the actual accuracy, and gives a factor of 10 to 100 between the two. A 0.5 m accuracy stored at 0.01 m resolution fits that rule, and storing it at 0.00001 m would imply a precision the survey never had.

The integrity column is not a number. Annex 14 defines three classes by the risk of using corrupted data. For routine data the probability that continued safe flight and landing would be severely at risk is very low. For the middle class it is low. For critical data it is high. Area 1 obstacle data is routine and the other three areas are in the middle class, which the text calls essential. ADR.OPS.A.010(c)(2) says that for that class corruption must not occur at any stage of the entire process, and additional processes are included as needed.

What each obstacle record carries

Accuracy is only one field. Annex 14 2.5.5 requires the geographical coordinates of obstacles in Area 2 within the aerodrome boundary and in Area 3 to be measured and reported to the AIS authority in degrees, minutes, seconds and tenths of seconds. It adds the top elevation, type, marking and lighting, if any, of each obstacle. AMC1 ADR.OPS.A.005(b) repeats this for the operator.

The reference systems are fixed by ADR.OPS.A.020. For air navigation, the operator shall use WGS-84 as the horizontal reference system and the mean sea level datum as the vertical one. A GNSS survey measures height above the ellipsoid , so a height for the data set needs a geoid model to turn it into a height above mean sea level. The UK CAA’s survey guidance, CAP 1732 section 2.5, asks for both orthometric and ellipsoidal elevations and warns that the separation between geoid and ellipsoid can introduce errors greater than the allowable ones. It is UK guidance, so read it as a worked example. The blog post on RTK, datums and disagreeing coordinates covers the same trap.

The data chain around the numbers

The numbers apply to the data at origination and have to survive the trip. ADR.OPS.A.010(a) says the quality requirements are complied with at data origination and maintained during transmission. Traceability, timeliness, completeness and format get their own lines, and GM1 to ADR.OPS.A.010(e) says traceability is supported by maintaining the metadata.

Where an outside surveyor originates the data, AMC2 ADR.OPS.A.010 expects formal arrangements with the entities providing survey data and electronic obstacle data. Its minimum content includes the quality requirement for each data item, the method for showing conformance, the action on a data error, the metadata and the continuity of data provision. GM1 sends contracted data origination to ATM/ANS.OR.085 of Regulation (EU) 2017/373. ADR.OPS.A.035(b) says data entered manually shall be subject to independent verification to detect errors.

At the far end, the State publishes. In November 2025 AIS of Georgia announced test obstacle data sets for Area 2 and Area 3 in AIXM 5.1.1, containing features defined in Doc 10066 and updated by AIRAC cycle. Each download is a zip that includes an XML file, a data product specification and a SHA-256 checksum. Official release for operational use is to be announced separately. The State’s AIP is the document where aerodrome information is published.

Where a drone survey fits

A drone survey measures obstacle positions and heights. The question for eTOD is whether it measures them to the Table 2 accuracy and can prove so. CAP 1732 section 2.4 says the survey report should include an analysis of accumulated error, evidence confirming the required accuracies have been met and the transformation parameters used. That is the standard a drone-derived data set would be held to. Section 2.4 also makes the data originator responsible for the accuracy of the control data and any transformation sets, which is where ground control and RTK or PPK positioning enter.

What the register can do now is narrower and still useful. It lists what is known, and a flown check finds what the list lacks. The blog post on surveying the approach and the PAPI protection surface check describe that work. An obstacle register typed in by hand and used to originate data for the AIS provider is subject to the independent verification in ADR.OPS.A.035(b).

Next to the FAA and the other standards pages

The ICAO Annex 14 page and the EASA CS-ADR-DSN page cover the lighting side of aerodrome rules. eTOD is the data side, and the numbers come from a different set of documents.

On the FAA side, AC 150/5300-13B Chg 1, dated 16 August 2024, says in paragraph 1.8.4 that the FAA uses aeronautical survey data to design and evaluate instrument flight procedures and, in part, to discover obstacles that could create a hazard to air navigation. Paragraph 1.8 refers to AC 150/5300-18 for calculation requirements. Paragraph K.1.4 says to use the standards in AC 150/5300-16, -17 and -18 to survey and compile data for instrument procedures. Their titles cover geodetic control, remote sensing technologies in airport surveys and submission of surveys to the National Geodetic Survey. They were not opened, so this page gives no FAA accuracy value and does not claim the FAA and ICAO tables match.