1、BRITISH STANDARD BS 7334-8: 1992 ISO 8322-8: 1992 Measuring instruments for building construction Part 8: Methods for determining accuracy in use of electronic distance-measuring instruments up to150m UDC 69.053:531.71:082.7:681.2.088BS7334-8:1992 This British Standard, having been prepared under th
2、e directionof the Technical Committee B/212, was publishedunder the authority ofthe Standards Board and comesinto effect on 15October1992 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference B/212 Draft for comment 90/15904 DC ISBN 0 580 21270 X Committee
3、s responsible for this BritishStandard The preparation of this British Standard was entrusted by the Technical Committee B/212, Tolerances, drawing practice, modular coordination, joints, project information, to Subcommittee B/212/1, Tolerances and accuracy, upon which the following bodies were repr
4、esented: British Constructional Steelwork Association Ltd. Chartered Institute of Building Department of the Environment (Building Research Establishment) Institution of Civil Engineers Royal Institute of British Architects Royal Institution of Chartered Surveyors Amendments issued since publication
5、 Amd. No. Date CommentsBS7334-8:1992 BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Normative reference 1 3 General 1 4 Accuracy specification of EDM instruments 1 5 Sources of error 2 6 State of adjustment 2 7 Test procedure for the accuracy i
6、n use of EDM instruments 4 8 Long-term stability 6 Annex A (informative) Systematic errors inherent in the instrument 7 Annex B (informative) Various EDM instruments and their unit lengths 16 Figure 1 Flow diagram for accuracy-in-use tests 3 Figure 2 Layout of measuring points 4 Figure A.1 Test line
7、 7 Figure A.2 Graphical representation of cyclic error 9 Figure A.3 Mean of the lines shown in Figure A.2 10 Table 1-A Example of field observations and calculation 5 Table 1-B Field observations and calculation 6 Table A.1 Suggested lengths 7 Table A.2-A Example of field observations and calculatio
8、n Zero correctionand cyclic correction 10 Table A.2-B Field observations and calculation Zero correction andcycliccorrection 11 Table A.3 Accepted values of the cyclic error of the measured distances 11 Table A.4-A Example of field observations and calculation, with zero correction 12 Table A.4-B Fi
9、eld observations and calculation with zero correction 13 Table A.5-A Example of field observations and calculation, with zero correction and cyclic correction 14 Table A.5-B Field observations and calculation, with zero correction and cyclic correction 15 List of references Inside back coverBS7334-8
10、:1992 ii BSI 01-2000 National foreword This Part of BS7334 has been prepared under the direction of Technical Committee B/212, Tolerances, drawing practice, modular coordination, joints, project information. It isidentical with ISO8322-8:1992 Building construction Measuring instruments Procedures fo
11、r determining accuracy in use Part8:Electronic distance-measuring instruments up to150m, published by the International Organization for Standardization (ISO). The series of Parts comprising BS7334will assist in ascertaining whether particular measuring equipment is appropriate to intended measuring
12、 tasks; they are also intended for assessing the accuracy in use of measuring instruments in general use on construction sites. The Parts are referred to in BS5606:1990 Guide to accuracy in building. ISO8322 consists of the following parts, under the general title Building construction Measuring ins
13、truments Procedures for determining accuracy in use: 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-measur
14、ing instruments up to150m; Part 9: Electronic distance-measuring instruments up to500m; Part 10: Testing short-range reflectors. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compli
15、ance with a British Standard does not of itself confer immunity from legal obligations. Cross-reference International Standard Corresponding British Standard ISO 4463-1:1989 BS5964 Building setting out and measurement Part 1:1990 Methods of measuring, planning and organization and acceptance criteri
16、a (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 18, an inside back cover 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 tabl
17、e on the inside front cover.BS7334-8:1992 BSI 01-2000 1 1 Scope This part of ISO8322 specifies test procedures to be adopted when determining and assessing the accuracy in use of electronic distance-measuring (EDM) equipment on building construction, for distances up to150m. The procedure applies to
18、 those types of EDM instruments used for surveying, control and compliance measurements and also when collecting accuracy data. Annex A gives examples of the determination of systematic errors. Annex B gives the unit lengths of various EDM instruments. 2 Normative reference The following standard co
19、ntains provisions which, through reference in this text, constitute provisions of this part of ISO8322. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this part of ISO8322are encouraged to investigate the possibi
20、lity of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO4463-1:1989, Measurement methods for building Setting-out and measurement Part1:Planning and organization, measuring procedures, acceptan
21、ce criteria. 3 General 3.1 Before commencing surveying, check and compliance measurements, when obtaining accuracy data or setting out, it is important that the operator investigate that the accuracy in use of the measuring equipment is appropriate to the intended measuring task. This International
22、Standard recommends that the operator carry out test measurements under field conditions to establish the accuracy achieved when he uses a particular EDM instrument with a particular prism or combination of prisms. The procedures assume that the particular EDM instrument and its ancillary equipment
23、are in known and acceptable state of permanent adjustment according to methods detailed in the manufacturers manuals. The accuracy in use is expressed in terms of the root mean square errors. The testing method described in this part of ISO8322 is carried out on a building site using calibrated stee
24、l tapes. The same method can also be applied on baselines, provided that the required distances are available or can be established. 3.2 Figure 1 indicates schematically the decisions to be made when establishing that the accuracy associated with a given surveying method and particular measuring equ
25、ipment is appropriate to the intended measuring task. Where the contract documentation specifies the required tolerance for the intended measuring task, it is recommended that this tolerance, which is normally given in termsof the permitted deviation P (P = 2,5 ) ofthe measuring task, be compared wi
26、th the accuracy-in-use data obtained either from previous accuracy-in-use tests or from general data A which indicate the expected accuracy in use of given measuring equipment. On those occasions that the previously obtained data indicate that the accuracy in use associated with the given measuring
27、equipment does not meet the specified permitted deviation of the measuring task, consideration 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 the rejection o
28、f a particular EDM equipment for a required measuring task, a second series of measurements should be carried out in accordance with clause 7, as indicated in Figure 1. If the second result is similar to the first one, the equipment in question should not be used for the required task, unless furthe
29、r investigations in accordance with Annex A can identify the main sources of systematic errors inherent in the instrument, and their values. 4 Accuracy specification of EDM instruments The accuracy of an EDM instrument together with its associated prism is often specified by the manufacturers as the
30、 sum (in millimetres) of a constant component a and a distance-related component b: whereis the root mean square error. EXAMPLE A manufacturer might specify the accuracy of an instrument by where d is the measured distance, in millimetres. . (1) . (2) or .(3) s BS7334-8:1992 2 BSI 01-2000 NOTE 1The
31、use of parts per million (ppm) has been retained in this International Standard as this is the term which appears on most instruments and in most instruction manuals. If the manufacturer has not specified the accuracy in the above form he should be requested to do so. Since in common construction wo
32、rk distances are usually short, i.e. shorter than 150m, the factor b in the right-hand term of formula (1) is neglected in this part of ISO8322. For longer distances it should be taken into account (see Annex A). The term a includes: the so-called zero error, caused by a lack of coincidence between
33、the mechanical and electro-optical centres of the instrument; the cyclic error, a systematic error occurring as a periodic function of the unit length, in general caused by electronic or optical disturbance when transmitted measuring signals are received. It is essential before the first use of the
34、instrument selected, and periodically thereafter, to verify that the instrument is performing within the manufacturers specification. The test procedures given in clause 7 are designed to do this with a minimum of additional work. 5 Sources of error The accuracy in use of an EDM instrument is affect
35、ed by factors other than the inherent ones of zero, scale and cyclic error. Some of these factors are centring errors; incorrect pointing; insufficient voltage; unsuitable signal strength 1) ; neglect of instructions given in the manufacturers manual; error in meteorological data; incorrect setting
36、of the meteorological switch; changes in the modulation frequency of the unit length; other unforeseen factors on site. Many errors can be reduced by following the correct surveying or maintenance procedures. Other errors are caused by ageing of certain components in the instrument. It is therefore
37、very important to check the instrument frequently. 6 State of adjustment Before any EDM instrument is used, the requirements given in 6.1 to 6.6 should be observed. 6.1 Instruction manual Read the instruction manual issued by the manufacturer for the particular EDM instrument. 6.2 Initial warm-up Th
38、e warming-up of the instrument shall be carried out in accordance with the instruction manual. 6.3 Frequency A change in the modulation frequency of the unit length is a cause of change of the scale factor. Frequencies should be verified using a calibrated frequency meter in accordance with national
39、 standards prior to delivery and checked from time to time thereafter and before carrying out any field calibration procedure. The accuracy of the frequency meter should be 1 10 6or better. The determination of the scale factor using long baselines involves the risk that the results will be influenc
40、ed by undetected meteorological factors. 6.4 Slope reduction Many EDM instruments can reduce the observed slope distance to the horizontal distance without any manual calculation. The accuracy of this feature can be checked by calculating the horizontal distance using the displayed slope distance an
41、d a relevant measured vertical angle. The vertical angle should be greater than 15 (15gon). 6.5 Correction for non-coaxial instruments A vertical separation between the line of collimation of the telescope of the theodolite and that of the EDM instrument affects the reduction of a short slope distan
42、ce to a horizontal one. The influence depends on the magnitude of the vertical angle and the vertical separation and should be calculated from the values for a specific set of equipment. 1) This can be either too low because of, for example, condensation or fog, or too high because of incorrect auto
43、matic reduction of the external signal. Assumptions: P is the permitted deviation of the measuring task A is the accuracy in use, generally expressed as deviation A; (both P and A are considered to include the dimensional variability associated with 2,5 times the standard deviation )are the root mea
44、n square errors obtained in the field tests s BS7334-8:1992 BSI 01-2000 3 6.6 Meteorological corrections Most EDM instruments have a direct input facility for meteorological data. The accuracy of this feature can be checked by measuring in the following way: Measure a distance D, (preferably about 1
45、50m) with a random value d of the input facility. Immediately after, measure the same distance with the value1,000006d. Repeat the sequence with value d and value 1,000006d three times. The means of the sets value d and value 1,000006d must differ by 0,000006d (i.e.9mm for150m). Figure 1 Flow diagra
46、m for accuracy-in-use testsBS7334-8:1992 4 BSI 01-2000 7 Test procedure for the accuracy in useofEDM instruments The following test procedure shall be adopted for determining the accuracy in use for a particular instrument and its ancillary equipment especially the prism (reflector) or combination o
47、f prisms (reflectors) to be used before starting work. Changing prisms can introduce additional errors. When setting up EDM equipment for different series of observations, special care shall be taken when centring both the instrument and the prism over the station. Easily achievable accuracies of ce
48、ntring expressed in terms of standard deviation are as follows. 7.1 Measurement of distances 7.1.1 Observation procedure 7.1.1.1 Establish a straight line of points in an approximately flat area, as shown in Figure 2. The points should be stable for the duration of the procedure including any repeat
49、 measurements or further investigations and should be clearly defined. The suggested lengths are: AB = 30,5m; AC = 42,5m; AD = 74,5m; AE = 86,5 m; AF = 158 m. 2) 7.1.1.2 Measure each distance twice using a calibrated tape in accordance with national standards corrected for temperature, tension and slope (see Table 1-A, columns 3 and 4) or using an EDM instrument with an accuracy of 1mm. Temperatures should preferably be measured using a contact thermometer. For e
