ASTM D4430-00(2023)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D4430 − 00 (Reapproved 2023)
Standard Practice for
Determining the Operational Comparability of
Meteorological Measurements
This standard is issued under the fixed designation D4430; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 Sensor systems used for making meteorological mea-
ization established in the Decision on Principles for the
surements may be tested for laboratory accuracy in environ-
Development of International Standards, Guides and Recom-
mental chambers or wind tunnels, but natural exposure cannot
mendations issued by the World Trade Organization Technical
be fully simulated. Atmospheric quantities are continuously
Barriers to Trade (TBT) Committee.
variable in time and space; therefore, repeated measurements
of the same quantities as required by Practice E177 to
2. Referenced Documents
determine precision are not possible. This practice provides
2.1 ASTM Standards:
standard procedures for exposure, data sampling, and process-
D1356 Terminology Relating to Sampling and Analysis of
ing to be used with two measuring systems in determining their
Atmospheres
operational comparability (1,2).
E177 Practice for Use of the Terms Precision and Bias in
1.2 The procedures provided produce measurement samples
ASTM Test Methods
that can be used for statistical analysis. Comparability is
defined in terms of specified statistical parameters. Other
3. Terminology
statistical parameters may be computed by methods described
3.1 For additional definitions of terms, refer to Terminology
in other ASTM standards or statistics handbooks (3).
D1356.
1.3 Where the two measuring systems are identical, that is,
3.2 Definitions of Terms Specific to This Standard:
same make, model, and manufacturer, the operational compa-
3.2.1 difference (D)—the difference between the systematic
rability is called functional precision.
difference (d) of a set of samples and the true mean (μ) of the
1.4 Meteorological determinations frequently require simul-
population:
taneous measurements to establish the spatial distribution of
D 5 d 2 μ (1)
atmospheric quantities or periodically repeated measurement to
3.2.2 systematic difference (d)—the mean of the differences
determine the time distribution, or both. In some cases, a
in the measurement by the two systems:
number of identical systems may be used, but in others a
N
mixture of instrument systems may be employed. The proce-
d 5 X 2 X (2)
~ !
( ai bi
dures described herein are used to determine the variability of
N
i51
like or unlike systems for making the same measurement.
3.2.3 operational comparability (C)—the root mean square
1.5 This standard does not purport to address the safety
(rms) of the difference between simultaneous readings from
concerns, if any, associated with its use. It is the responsibility
two systems measuring the same quantity in the same environ-
of the user of this standard to establish appropriate safety,
ment:
health, and environmental practices and determine the appli-
N
cability of regulatory limitations prior to use. (See 8.1 for more
C 5 6 X 2 X (3)
Π~ !
( ai bi
N
specific safety precautionary information.) i51
where:
X = ith measurement made by one system,
ai
This practice is under the jurisdiction of ASTM Committee D22 on Air Quality
and is the direct responsibility of Subcommittee D22.11 on Meteorology.
Current edition approved Jan. 1, 2023. Published February 2023. Originally
approved in 1984. Last previous edition approved in 2015 as D4430 – 00 (2015). For referenced ASTM standards, visit the ASTM website, www.astm.org, or
DOI: 10.1520/D4430-00R23. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
The boldface numbers in parentheses refer to the list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
this practice. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4430 − 00 (2023)
4.5 The root mean square (rms) of the measurement differ-
X = ith simultaneous measurement made by another
bi
ences is calculated to provide operational comparability or
system, and
functional precision of the systems.
N = number of samples used.
4.6 Measurement differences may change with the magni-
3.2.3.1 functional precision—the operational comparability
tude of the measurement (for example, the absolute value of
of identical systems.
the difference in the measurement of wind speed by two
3.2.4 estimated standard deviation of the difference (s)—a
systems may be greater or smaller at high-wind speeds than at
measure of the dispersion of a series of differences around their
low-wind speeds). To test the data for such dependence, the
mean.
range of measurements shall be divided into no less than three
2 2
s 5 6=C 2 d (4)
class intervals and each class shall have a sufficient number of
3.2.5 skewness (M)—the symmetry of the distribution (the samples to represent the class. The change in rms difference
third moment about the mean). between classes indicates the dependence of the measurement
difference on the magnitude of the measurement.
N
X 2 X 2 d
~~ ! !
( ai bi
i51
5. Significance and Use
M 5 (5)
N
5.1 This practice provides data needed for selection of
M = 0 for normal distribution.
instrument systems to measure meteorological quantities and to
3.2.6 kurtosis (K)—the peakedness of the distribution (the
provide an estimate of the precision of measurements made by
fourth moment about the mean), K = 3 for normal distribution.
such systems.
N
5.2 This practice is based on the assumption that the
X 2 X 2 d
~~ ! !
( ai bi
i51 repeated measurement of a meteorological quantity by a sensor
K 5 (6)
N
system will vary randomly about the true value plus an
unknowable systematic difference. Given infinite resolution,
3.2.7 response time (T)—the time required for the change in
these measurements will have a Gaussian distribution about the
output of a measuring system to reach 63 % of a step function
systematic difference as defined by the Central Limit Theorem.
change in the variable being measured.
If it is known or demonstrated that this assumption is invalid
3.2.8 identical systems—systems of the same make and
for a particular quantity, conclusions based on the characteris-
model produced by the same manufacturer.
tics of a normal distribution must be avoided.
3.2.9 resolution (r)—the smallest change in an atmospheric
variable that is reported as a change in the measurement.
6. Interferences
4. Summary of Practice
6.1 Exposure of the systems shall be such as to avoid
interference from sources, structures, or other conditions that
4.1 The systems to be compared must make measurements
may produce a gradient in the measurement across the sample
within a cylindrical volume of the ambient atmosphere not
volume.
greater than 10 m in horizontal diameter. The vertical extent of
the volume must be the lesser of 1 m or one-tenth H, where H
6.2 A mutual interference by systems may produce a sys-
is the height above the earth’s surface of the base of the
tematic difference (d) or bias that would not occur if one
volume. The sample volume must be selected to ensure
system were used by itself. That bias is not a part of the
homogeneous distribution of the variable being measured.
comparability and must be reported separately.
4.2 For some measurements (for example, visibility) the
6.3 A systematic difference greater than one increment of
horizontal distance or the height (for example, cloud height)
resolution must be investigated by interchanging the position
may be the variable of interest. In the first case, one of the two
of the sensors w
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