1、BRITISH STANDARD BS 7334-1: 1990 ISO 8322-1: 1989 Incorporating Amendment No. 1 Measuring instruments for building construction Part 1: Methods for determining accuracy in use: TheoryBS7334-1:1990 This British Standard, having been prepared under the directionof the Basic Data andPerformance Criteri
2、a for CivilEngineering and Building Structures Standards Policy Committee, was published underthe authority of the BoardofBSI and comes into effect on 30 September 1990 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference BDB/4 Draft for comment 87/10240
3、DC ISBN 0 580 18695 4 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Basic Data and Performance Criteria for Civil Engineering and Building Structures Standards Policy Committee (BDB/-) to Technical Committee BDB/4, upon which the follo
4、wing bodies were represented: Association of County Councils British Standards Society Building Employers Confederation Chartered Institution of Building Services Engineers Concrete Society Department of Education and Science Department of the Environment (Building Research Establishment) Department
5、 of the Environment (Property Services Agency) Incorporated Association of Architects and Surveyors Institute of Building Control Institute of Clerks of Works of Great Britain Inc. Institution of Civil Engineers Institution of Structural Engineers Institution of Water and Environmental Management Ro
6、yal Institute of British Architects Royal Institution of Chartered Surveyors The following body was also represented in the drafting of the standard, through subcommittees and panels: Chartered Institute of Building Amendments issued since publication Amd. No. Date Comments 9317 November 1996 Indica
7、ted by a sideline in the marginBS7334-1:1990 BSI 12-1999 i Contents Page Committees responsible Inside front cover National foreword ii 0 Introduction 1 1 Scope 1 2 Field of application 1 3 References 1 4 General 1 5 Formulae 4 Figure 1 Flow diagram for accuracy in use tests 3 Publications referred
8、to Inside back coverBS7334-1:1990 ii BSI 12-1999 National foreword This Part of BS 7334 has been prepared under the direction of the Basic Data and Performance Criteria for Civil Engineering and Building Structures Standards Policy Committee. It is identical with ISO8322-1:1989 “Building constructio
9、n Measuring instruments Procedures for determining accuracy in use Part1: Theory” published by the International Organization for Standardization (ISO); and gives the basic theory for the analysis of the test results for particular measuring instruments for which testing procedures are described in
10、the subsequent Parts of BS7334. The series of Parts comprising BS7334 will assist in ascertaining whether particular measuring equipment is appropriate to intended measuring tasks; they are also intended for assessing the accuracy in use of measuring instruments in general use on construction sites.
11、 Part 1:1990, Theory. Part 2:1990, Measuring tapes. Part 3:1990, Optical levelling instruments. Part 4:1992, Theodolites. Part 5:1992, Optical plumbing instruments. Part 6:1992, Laser instruments. Part 7:1992, Instruments when used for setting out. Part 8:1992, Electronic distance-measuring instrume
12、nts up to150m. The parts are referred to in BS5606:1990 “Guide to accuracy in building”. The Technical Committee has reviewed the provisions of ISO7077, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. Cross-references Intern
13、ational Standard Corresponding British Standard BS ISO 3534 Statistics, vocabulary and symbols ISO 3534-1:1993 BS ISO 3534-1:1993 Probability and general statistical terms (Identical) ISO 3534-3:1985 BS ISO 3534-3:1985 Glossary of terms relating to the design of experiments (Identical) BS 5964 Build
14、ing setting out and measurement ISO 4463-1:1989 Part 1:1990 Methods of measuring, planning and organization and acceptance criteria (Identical) ISO 4463-2:1995 Part 2:1996 Measuring stations and targets (Identical) ISO 4463-3:1995 Part 3:1996 Check-lists for the procurement of surveys and measuremen
15、t services (Identical) ISO 7078:1985 BS 6953:1988 Glossary of terms for procedures for setting out, measurement and surveying in building construction (including guidance notes) (Identical)BS7334-1:1990 BSI 12-1999 iii A British Standard does not purport to include all the necessary provisions of a
16、contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to 6, an inside back c
17、over and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blankBS7334-1:1990 BSI 12-1999 1 0 Introduction This International Standard consists of a series of parts sp
18、ecifying test procedures to be adopted when determining and assessing the accuracy in use of measuring instruments in building construction. The first part gives the theory; subsequent parts give the procedures for determining the accuracy in use of measuring instruments for measurements. The comple
19、te series will consist of the following parts: Part 1: Theory; Part 2: Measuring tapes; Part 3: Optical levelling instruments; Part 4: Theodolites; Part 5: Optical plumbing instruments; Part 6: Laser instruments; Part 7: Instruments when used for setting out; Part 8: Electronic distance-measuring in
20、struments. Other International Standards for testing measuring instruments for land surveying purposes, and for measuring procedures in ordnance survey, are in preparation. 1 Scope This part of ISO8322 gives the formulae used in the specification of test procedures to be adopted for the determinatio
21、n and assessment of the accuracy in use of measuring instruments. 2 Field of application The theory given in this part of ISO8322 applies to the procedures used in building construction when determining and assessing the accuracy of surveying, check and compliance measurements, setting out, checking
22、 processes or when obtaining accuracy data. These procedures assume the use of measuring methods in which the systematic errors can be largely compensated for or disregarded. 3 References ISO 3534, Statistics Vocabulary and symbols. ISO 4463-1, Measurement methods for building Setting-out and measur
23、ement Part 1: Planning and organization, measuring procedures, acceptance criteria. ISO 7077, Measuring methods for building General principles and procedures for the verification of dimensional compliance. ISO 7078, Building construction Procedures for setting out, measurement and surveying Vocabul
24、ary and guidance notes. 4 General 4.1 Before commencing surveying, check and compliance measurements, when obtaining accuracy data or setting out, it is important that the operator investigates that the accuracy in use of the measuring equipment is appropriate to the intended measuring task. This In
25、ternational Standard recommends that the operator carries out test measurements under field conditions to establish the accuracy achieved when he uses a particular instrument and its ancillary equipment. To ensure that the assessment takes account of various environmental influences, two series of m
26、easurements need to be carried out under different conditions. The particular conditions to be taken into account may vary depending on where the tasks are to be undertaken. These conditions will include variations in air temperature, wind speed, cloud cover and visibility. Note should also be made
27、of the actual weather conditions at the time of measurement and the type of surface over which the measurements are made. The sets of conditions chosen for the tests should match those expected when the intended measuring task is actually carried out. See ISO7077 and ISO7078. Successive parts of thi
28、s International Standard give detailed procedures for determining the accuracy in use for specific types of instruments. For those instruments not covered in a separate part, the theory given in this part can be used as a basis for devising suitable test procedures. In such cases the minimum values
29、taken for m and n should be4and30respectively (see5.1 and5.2). Such test procedures should be carried out over the range of measurements for which the instrument is to be used. For each of the tests to be adopted for different tasks and described in detail in parts2to8of this International Standard,
30、 the preferred minimum sample size is indicated in the relevant clauses. However, if particular circumstances dictate the acceptance of smaller sample sizes, this must be in the knowledge that the assessment will be less reliable. All procedures are designed so that the systematic errors are largely
31、 eliminated and assume that the particular instruments are in known and acceptable states of user adjustment according to methods detailed in the manufacturers handbooks. Accuracy in use procedures require repeat tests to be made with the same instrumentation and the same observer, within a short in
32、terval of time. These are “repeatability conditions” as defined in ISO3534.BS7334-1:1990 2 BSI 12-1999 The accuracy in use is expressed in terms of the standard deviation. 4.2 The figure indicates schematically the decisions to be made when establishing that the accuracy associated with a given surv
33、eying method and particular measuring equipment is appropriate to the intended measuring task. In particular, the decisions apply when adopted by a particular operator under a range of environmental conditions which are likely to occur when the task is actually carried out. Where the contract docume
34、ntation specifies the required tolerance for the intended measuring task, it is recommended that this tolerance, which is normally given in terms of the permitted deviation P(P = 2,5 ) of the measuring task, is compared with the accuracy in use data obtained either from previous accuracy in use test
35、s or from general data A which indicate the expected accuracy in use of given measuring equipment. On those occasions that the previously obtained data indicates that the accuracy in use associated with the given measuring equipment exceeds the specified permitted deviation of the measuring task, co
36、nsideration should be given to either selecting a different method and/or a more precise instrument, or discussing with the designer the need for such a small permitted deviation. See ISO4463-1. Before obtaining an overall estimate of the accuracy in use, it is recommended that each standard deviati
37、on for a given series of measurements undertaken under particular environmental conditions is compared, as indicated in the figure, with the specified permitted deviation. Where the comparison shows that the specified permitted deviation has not been achieved for one series of measurements, an addit
38、ional series of measurements should be carried out under as near as possible similar environmental conditions to those which applied in that original series of measurements.BS7334-1:1990 BSI 12-1999 3 Assumptions: P is the permitted deviation of the measuring task A is the accuracy in use, generally
39、 expressed as deviation A; (both P and A are considered to include the dimensional variability associated with 2,5 times the standard deviation ) s are the deviations obtained in the field tests Figure 1 Flow diagram for accuracy in use testsBS7334-1:1990 4 BSI 12-1999 5 Formulae The following formu
40、lae are required for use at the evaluation stage of most of the procedures given in the subsequent parts of this International Standard. They indicate how the achieved accuracy in use, expressed in terms of standard deviation or mean square error, is estimated by first calculating the individual sta
41、ndard deviations or mean square errors for each of the series of measurements and then by combining statistically each of these individual standard deviations or mean square errors. The formulae are given in general terms such that the number of series of measurements and the number of individual me
42、asurements within each series is not defined explicitly. 5.1 Calculation of the standard deviation for a single series of measurements using mean values 5.1.1 Let n jbe the number of measurements in the jth series. 5.1.2 Let x ijbe the value of the ith measurement of the jth series. 5.1.3 The arithm
43、etic mean,of the values measured in the jth series of measurement is 5.1.4 Let v ijbe the deviation of the value of the ith measurement from the arithmetic mean within the jth series of measurements. Thus v ij= x ij To minimize the effect of rounding errors, the calculation of each division v should
44、 be carried out to the nearest0,1value of the last observed digit. As an arithmetic check the sum of the deviations should be zero. 5.1.5 Let be the sum of squares of all the deviations (v ij ) within the jth series of measurements. Thus 5.1.6 Let f jbe the number of degrees of freedom for the jth s
45、eries of measurements, where f j= n j 1 5.1.7 Let s jbe the standard deviation for the jth series of measurements, where s jis calculated thus 5.2 Calculation of the overall standard deviation for several series of measurements using mean values The standard deviation obtained for each of the jth se
46、ries of measurements is considered to be a separate estimate of the overall standard deviation of the measurement. It is assumed that each of these estimates is equally valid. The following formulae indicate how the individual standard deviations are combined to give one overall standard deviation w
47、hich takes equal account of the standard deviations calculated for each series of measurements. 5.2.1 Let m be the number of series of measurements. 5.2.2 As the true value of each of the m measurements series cannot be determined, the arithmetic mean of each series is accepted as the best estimate
48、of the true value. 5.2.3 Let s be the overall estimate of the standard deviation, where s is calculated thus 5.3 Calculation of the standard deviation for a single series of measurements using double observations 5.3.1 Let n jbe the number of a double observation set in the jth series. 5.3.2 Let x i
49、j1and x ij2be the values of the ith set of the double observations in the jth series. 5.3.3 Let d ijbe the difference of the two values of the double measurements of the ith set of the jth series d ij= x ij1 x ij2 5.3.4 Letbe the sum of square of all differences d ijwithin the jth series of measurements. Thus x xBS7334-1:1990 BSI 12-1999 5 5.3.5 Let s jbe the standard deviation for the jth series of measurements, where s jis calculated thus 5.4 Calculation of the overall standard deviation for several se
