Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 1: Conceptual basis for measurements (ISO 20785-1:2020)

This document specifies the conceptual basis for the determination of ambient dose equivalent for the
evaluation of exposure to cosmic radiation in civilian aircraft and for the calibration of instruments
used for that purpose.

Dosimetrie zu Expositionen durch kosmische Strahlung in Flugzeugen der zivilen Luftfahrt - Teil 1: Konzeptionelle Grundlage für Messungen (ISO 20785-1:2020)

Dieses Dokument legt die konzeptionelle Grundlage für die Bestimmung der Umgebungs-Äquivalentdosis zur Bestimmung der Exposition durch kosmische Strahlung in zivilen Luftfahrzeugen sowie für die Kalibrierung von für diesen Zweck verwendeten Geräten fest.

Dosimétrie pour l'exposition au rayonnement cosmique à bord d'un avion civil - Partie 1: Fondement théorique des mesurages (ISO 20785-1:2020)

Le présent document spécifie les principes de base permettant de déterminer l'équivalent de dose ambiant pour l'évaluation de l'exposition au rayonnement cosmique à bord d'un avion civil, ainsi que pour l'étalonnage des instruments utilisés à cette fin.

Dozimetrija za merjenje izpostavljenosti kozmičnemu sevanju v civilnem letalskem prometu - 1. del: Konceptualna osnova za meritve (ISO 20785-1:2020)

General Information

Status
Published
Public Enquiry End Date
23-Apr-2019
Publication Date
13-Aug-2020
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
13-Aug-2020
Due Date
18-Oct-2020
Completion Date
14-Aug-2020

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SLOVENSKI STANDARD
SIST EN ISO 20785-1:2020
01-oktober-2020
Nadomešča:
SIST EN ISO 20785-1:2017
Dozimetrija za merjenje izpostavljenosti kozmičnemu sevanju v civilnem letalskem
prometu - 1. del: Konceptualna osnova za meritve (ISO 20785-1:2020)

Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 1: Conceptual basis

for measurements (ISO 20785-1:2020)
Dosimetrie zu Expositionen durch kosmische Strahlung in Flugzeugen der zivilen
Luftfahrt - Teil 1: Konzeptionelle Grundlage für Messungen (ISO 20785-1:2020)

Dosimétrie pour l'exposition au rayonnement cosmique à bord d'un avion civil - Partie 1:

Fondement théorique des mesurages (ISO 20785-1:2020)
Ta slovenski standard je istoveten z: EN ISO 20785-1:2020
ICS:
13.280 Varstvo pred sevanjem Radiation protection
49.020 Letala in vesoljska vozila na Aircraft and space vehicles in
splošno general
SIST EN ISO 20785-1:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 20785-1:2020
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SIST EN ISO 20785-1:2020
EN ISO 20785-1
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2020
EUROPÄISCHE NORM
ICS 13.280; 49.020 Supersedes EN ISO 20785-1:2017
English Version
Dosimetry for exposures to cosmic radiation in civilian
aircraft - Part 1: Conceptual basis for measurements (ISO
20785-1:2020)

Dosimétrie pour l'exposition au rayonnement Dosimetrie für die Belastung durch kosmische

cosmique à bord d'un avion civil - Partie 1: Fondement Strahlung in Zivilluftfahrzeugen - Teil 1:

théorique des mesurages (ISO 20785-1:2020) Konzeptionelle Grundlage für Messungen (ISO 20785-

1:2020)
This European Standard was approved by CEN on 1 July 2020.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20785-1:2020 E

worldwide for CEN national Members.
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SIST EN ISO 20785-1:2020
EN ISO 20785-1:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 20785-1:2020
EN ISO 20785-1:2020 (E)
European foreword

This document (EN ISO 20785-1:2020) has been prepared by Technical Committee ISO/TC 85 "Nuclear

energy, nuclear technologies, and radiological protection" in collaboration with Technical Committee

CEN/TC 430 “Nuclear energy, nuclear technologies, and radiological protection” the secretariat of

which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by February 2021, and conflicting national standards

shall be withdrawn at the latest by February 2021.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN ISO 20785-1:2017.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 20785-1:2020 has been approved by CEN as EN ISO 20785-1:2020 without any

modification.
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SIST EN ISO 20785-1:2020
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SIST EN ISO 20785-1:2020
INTERNATIONAL ISO
STANDARD 20785-1
Third edition
2020-07
Dosimetry for exposures to cosmic
radiation in civilian aircraft —
Part 1:
Conceptual basis for measurements
Dosimétrie pour l'exposition au rayonnement cosmique à bord d'un
avion civil —
Partie 1: Fondement théorique des mesurages
Reference number
ISO 20785-1:2020(E)
ISO 2020
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SIST EN ISO 20785-1:2020
ISO 20785-1:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST EN ISO 20785-1:2020
ISO 20785-1:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

3.1 General terms ........................................................................................................................................................................................... 1

3.2 Quantities and units ........................................................................................................................................................................... 2

3.3 Atmospheric radiation field ......................................................................................................................................................... 4

4 General considerations .................................................................................................................................................................................. 6

4.1 The cosmic radiation field in the atmosphere ............................................................................................................. 6

4.2 General calibration considerations for the dosimetry of cosmic radiation fields in

aircraft ............................................................................................................................................................................................................ 7

4.2.1 Approach ................................................................................................................................................................................ 7

4.2.2 Considerations concerning the measurement ....................................................................................... 7

4.2.3 Considerations concerning the radiation field ...................................................................................... 8

4.2.4 Considerations concerning calibration ........................................................................................................ 8

4.2.5 Simulated aircraft fields ............................................................................................................................................ 9

4.3 Conversion coefficients .................................................................................................................................................................... 9

5 Dosimetric devices ..........................................................................................................................................................................................10

5.1 Introduction ...........................................................................................................................................................................................10

5.2 Active devices ........................................................................................................................................................................................10

5.2.1 Devices to determine all field components ............................................................................................10

5.2.2 Devices for low LET/non-neutron .................................................................................................................11

5.2.3 Devices for high-LET/neutron component ............................................................................................12

5.3 Passive devices .....................................................................................................................................................................................13

5.3.1 General considerations ............................................................................................................................................13

5.3.2 Etched track detectors .............................................................................................................................................14

5.3.3 Fission foil detectors .................................................................................................................................................14

5.3.4 Superheated emulsion neutron detectors (bubble) detectors ..............................................14

5.3.5 Thermoluminescent detectors..........................................................................................................................15

5.3.6 Photoluminescent detectors ...............................................................................................................................15

Annex A (informative) Representative particle fluence rate energy distributions for

the cosmic radiation field at flight altitudes for solar minimum and maximum

conditions and for minimum and maximum vertical cut-off rigidity ........................................................16

Bibliography .............................................................................................................................................................................................................................22

© ISO 2020 – All rights reserved iii
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SIST EN ISO 20785-1:2020
ISO 20785-1:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www .iso .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies,

and radiological protection, Subcommittee SC 2, Radiation protection.

This third edition cancels and replaces the second edition (ISO 20785-1:2012), which has been

technically revised. The main changes are as follows:
— revision of the terms and definitions;
— updated references.
A list of all the parts in the ISO 20785 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
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SIST EN ISO 20785-1:2020
ISO 20785-1:2020(E)
Introduction

Aircraft crews are exposed to elevated levels of cosmic radiation of galactic and solar origin and

secondary radiation produced in the atmosphere, the aircraft structure and its contents. Following

recommendations of the International Commission on Radiological Protection (ICRP) in Publication

[1] [2]

60 , confirmed by Publication 103 , the European Union (EU) introduced a revised Basic Safety

[3] [4]

Standards Directive and International Atomic Energy Agency (IAEA) issued a revised Basic Safety

Standards. Those standards included exposure to natural sources of ionizing radiation, including cosmic

radiation, as occupational exposure. The EU Directive requires account to be taken of the exposure of

aircraft crews liable to receive more than 1 mSv per year. It then identifies the following four protection

measures:
a) to assess the exposure of the crew concerned;

b) to take into account the assessed exposure when organizing working schedules with a view to

reducing the doses of highly exposed crews;
c) to inform the workers concerned of the health risks their work involves; and

d) to apply the same special protection during pregnancy to female crews in respect of the "child to be

born" as to other female workers.

The EU Council Directive has already been incorporated into laws and regulations of EU Member States

and is being included in the aviation safety standards and procedures of the Joint Aviation Authorities

and the European Air Safety Agency. Other countries such as Canada and Japan have issued advisories

to their airline industries to manage aircraft crew exposure.

For regulatory and legislative purposes, the radiation protection quantities of interest are the

equivalent dose (to the foetus) and the effective dose. The cosmic radiation exposure of the body is

essentially uniform and the maternal abdomen provides no effective shielding to the foetus. As a

result, the magnitude of equivalent dose to the foetus can be set equal to that of the effective dose

received by the mother. Doses on board aircraft are generally predictable, and events comparable to

unplanned exposure in other radiological workplaces cannot normally occur (with the rare exceptions

of extremely intense and energetic solar particle events). Personal dosimeters for routine use are not

considered necessary. The preferred approach for the assessment of doses of aircraft crews, where

necessary, is to calculate directly the effective dose per unit time, as a function of geographic location,

altitude and solar cycle phase, and to combine these values with flight and staff roster information to

obtain estimates of effective doses for individuals. This approach is supported by guidance from the

[5] [6]
European Commission and the ICRP in Publications 75 and 132 .

The role of calculations in this procedure is unique in routine radiation protection and it is widely

accepted that the calculated doses should be validated by measurement. The effective dose is not

directly measurable. The operational quantity of interest is ambient dose equivalent, H*(10). In order

to validate the assessed doses obtained in terms of effective dose, calculations can be made of ambient

dose equivalent rates or route doses in terms of ambient dose equivalent, and values of this quantity

determined from measurements. Traceability should be provided for a reasonable number of particle

types and energies of the atmospheric radiation field, corrections included for differences between the

calibration fields and the total atmospheric radiation field, and related uncertainties properly taken

into account. The validation of calculations of ambient dose equivalent for a particular calculation

method may be taken as a validation of the calculation of the effective dose by the same computer code,

but this step in the process may need to be confirmed. The alternative is to establish a priori that the

operational quantity ambient dose equivalent is a good estimator of effective dose and equivalent dose

to the foetus for the radiation fields being considered, in the same way that the use of the operational

quantity personal dose equivalent is justified for the estimation of effective dose for ground-based

radiation workers.

The radiation field in aircraft at altitude is complex, with many types of ionizing radiation present, with

energies ranging up to many GeV. The determination of ambient dose equivalent for such a complex

radiation field is difficult. In many cases, the methods used for the determination of ambient dose

© ISO 2020 – All rights reserved v
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SIST EN ISO 20785-1:2020
ISO 20785-1:2020(E)

equivalent in aircraft are similar to those used at high-energy accelerators in research laboratories.

Therefore, it is possible to recommend dosimetric methods and methods for the calibration of dosimetric

devices, as well as the techniques for maintaining the traceability of dosimetric measurements to

national standards. Dosimetric measurements made to evaluate ambient dose equivalent should be

performed using accurate and reliable methods that ensure the quality of readings provided to workers

and regulatory authorities. This document gives a conceptual basis for the characterization of the

response of instruments for the determination of ambient dose equivalent in aircraft.

Requirements for the determination and recording of the cosmic radiation exposure of aircraft

crews have been introduced into the national legislation of EU Member States and other countries.

Harmonization of methods used for determining ambient dose equivalent and for calibrating instruments

is desirable to ensure the compatibility of measurements performed with such instruments.

This document is intended for the use of primary and secondary calibration laboratories for ionizing

radiation, by radiation protection personnel employed by governmental agencies, and by industrial

corporations concerned with the determination of ambient dose equivalent for aircraft crews.

vi © ISO 2020 – All rights reserved
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SIST EN ISO 20785-1:2020
INTERNATIONAL STANDARD ISO 20785-1:2020(E)
Dosimetry for exposures to cosmic radiation in civilian
aircraft —
Part 1:
Conceptual basis for measurements
1 Scope

This document specifies the conceptual basis for the determination of ambient dose equivalent for the

evaluation of exposure to cosmic radiation in civilian aircraft and for the calibration of instruments

used for that purpose.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1 General terms
3.1.1
calibration

operation that, under specified conditions, establishes a relation between the conventional quantity,

H , and the indication, G

Note 1 to entry: A calibration can be expressed by a statement, calibration function, calibration diagram,

calibration curve, or calibration table. In some cases, it can consist of an additive or multiplicative correction of

the indication with associated measurement uncertainty.

Note 2 to entry: Calibration should not be confused with adjustment of a measuring system, often mistakenly

called "self-calibration", or with verification of calibration.

Note 3 to entry: Often, the first step alone in the above definition is perceived as being calibration.

3.1.2
response
response characteristic

quotient of the indication, G, or the corrected indication, G , and the conventional quantity value to be

corr
measured

Note 1 to entry: To avoid confusion, it is necessary to specify which of the quotients, given in the definition of

the response (to G or to G ) is applied. Furthermore, it is necessary, in order to avoid confusion, to state the

corr

quantity to be measured, for example: the response with respect to fluence, R , the response with respect to

kerma, R , the response with respect to absorbed dose, R .
K D
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SIST EN ISO 20785-1:2020
ISO 20785-1:2020(E)

Note 2 to entry: The reciprocal of the response under the specified conditions is equal to the calibration

coefficient N
coeff.

Note 3 to entry: The value of the response can vary with the magnitude of the quantity to be measured. In such

cases the detector assembly's response is said to be non-constant.

Note 4 to entry: The response usually varies with the energy and direction distribution of the incident

radiation. It is, therefore, useful to consider the response as a function, R(E,Ω), of the radiation energy, E, and

of the direction, Ω of the incident monodirectional radiation. R(E) describes the "energy dependence" and R(Ω)

the "angle dependence" of response; for the latter, Ω may be expressed by the angle, α, between the reference

direction of the detector assembly and the direction of an external monodirectional field.

3.2 Quantities and units
3.2.1
particle fluence
fluence

number, dN, at a given point in space, of particles incident on a small spherical domain, divided by the

cross-sectional area, da, of that domain:
−2 −2
Note 1 to entry: The unit of the fluence is m ; a frequently used unit is cm .

Note 2 to entry: The energy distribution of the particle fluence, Φ , is the quotient, dΦ, by dE, where dΦ is

the fluence of particles of energy between E and E+dE. There is an analogous definition for the direction

distribution, Φ , of the particle fluence. The complete representation of the double differential particle fluence

can be written (with arguments) Φ (E,Ω), where the subscripts characterize the variables (quantities) for

E,Ω

differentiation and where the symbols in the brackets describe the values of the variables. The values in the

brackets are needed for special function values, e.g. the energy distribution of the particle fluence at energy

E = E is written as Φ (E ). If no special values are indicated, the brackets may be omitted.

0 E 0
3.2.2
particle fluence rate
fluence rate
rate of the particle fluence (3.2.1) expressed as
dΦ d N
Φ ==
dt ddat⋅

where dΦ is the increment of the particle fluence during an infinitesimal time interval with duration dt.

−2 −1 −2 −1

Note 1 to entry: The unit of the fluence rate is m s , a frequently used unit is cm s .

3.2.3
absorbed dose
for any ionizing radiation,

where dε is the mean energy imparted by ionizing radiation to an element of irradiated matter of mass

Note 1 to entry: In the limit of a small domain, the mean specific energy is equal to the absorbed dose.

Note 2 to entry: The unit of absorbed dose is J kg , with the special name gray (Gy).

2 © ISO 2020 – All rights reserved
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SIST EN ISO 20785-1:2020
ISO 20785-1:2020(E)
3.2.4
kerma

for indirectly ionizing (uncharged) particles, the mean sum of the initial kinetic energies dE of all the

charged ionizing particles liberated by uncharged ionizing particles in an element of matter, divided by

the mass dm of that element:

Note 1 to entry: Quantity dE includes the kinetic energy of the charged particles emitted in the decay of excited

atoms or molecules or nuclei.
Note 2 to entry: The unit of kerma is J kg , with the special name gray (Gy).
3.2.5
dose equivalent
at the point of interest in tissue,
HD= Q
where
D is the absorbed dose;
Q is the quality factor at that point, and
HQ= ()LD dL
L=0

Note 1 to entry: Q is determined by the unrestricted linear energy transfer, L (often denoted as L or LET), of

charged particles passing through a small volume element (domains) at this point (the value of L is given for

charged particles in water, not in tissue; the difference, however, is small). The dose equivalent at a point in tissue

is then given by the above formula, where D = dD/dL is the distribution in terms of L of the absorbed dose at the

point of interest.
[2]

Note 2 to entry: The relationship of Q and L is given in ICRP Publication 103 (ICRP, 2007) .

Note 3 to entry: The unit of dose equivalent is J kg , with the special name sievert (Sv).

3.2.6
lineal energy

quotient of the energy, ε , imparted to the matter in a given volume by a single energy deposition event,

by the mean chord length, l , in that volume:
−1 −1

Note 1 to entry: The unit of lineal energy is J m , a frequently used unit is keV μm .

3.2.7
dose-mean lineal energy
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SIST EN ISO 20785-1:2020
ISO 20785-1:2020(E)
expectation
yy= dy()dy
where d(y)is the dose probability density of y.

Note 1 to entry: The dose probability density of y is given by d( y), where d( y)dz is the fraction of absorbed dose

delivered in single events with lineal energy in the interval from y to y+dy.

Note 2 to entry: Both the dose-mean lineal energy and distribution d( y) are independent of the absorbed dose or

dose rate.
3.2.8
ambient dose equivalent
H*(10)

dose equivalent (3.2.5) at a point in a radiation field, that would be produced by the corresponding

expanded and aligned field, in the ICRU sphere at 10 mm depth on the radius opposing the direction of

the aligned field

Note 1 to entry: The unit of ambient dose equivalent is J kg with the special name sievert (Sv).

3.2.9
standard barometric altitude
pressure altitude

altitude determined by a barometric altimeter calibrated (3.1.1) with reference to the International

[7]

Standard Atmosphere (ISA) (ISO 2533 , Standard Atmosphere) when the altimeter's datum is set to

1 013,25 hPa

Note 1 to entry: ISO/IEC Directives Part 2 Clause 9 requires ISO documents to use SI units and to conform with

[8]

ISO 80000 so the default should be metres. However, in aviation, the flight level is mostly given as FLxxx, where

xxx is a three-digit number representing multiples of 100 feet of pressure altitude, based on the ISA and a datum

setting of 1013,25 hPa; for instance FL350 corresponds to 35 000 ft or,
...

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