# ISO 5456-4-1996

Disclosure to Promote the Right To InformationWhereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public. इंटरनेट मानक“!ान $ एक न’ भारत का +नम-ण”Satyanarayan Gangaram Pitroda“Invent a New India Using Knowledge”“प0रा1 को छोड न’ 5 तरफ”Jawaharlal Nehru“Step Out From the Old to the New”“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan“The Right to Information, The Right to Live”“!ान एक ऐसा खजाना जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam“Knowledge is such a treasure which cannot be stolen”ैIS 15021-4 (2001): Technical Drawings - Projection Methods,Part 4: General Projection [PGD 24: Drawings]IS 15021 (Part 4): 2001ISO 5456-4:1996Indian StandardTECHNICAL DRAWINGS — PROJECTION METHODSPART 4 CENTRAL PROJECTIONIcs 01.100.01@ BIS 2001BUREAU OF IN DI AN STAN DARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARGNEW DELHI 110002December 2001 Price Group 11Drawings Sectional Committee, BP 24NATIONAL FOREWORDThis Indian Standard (Part 4) which is identical with ISO 5456-4 : 1996 ‘Technical drawings —Projection methods — Part 4: Central projection’ issued by the International Organization forStandardization (ISO) was adopted by the Bureau of Indian Standards on the recommendation ofDrawings Sectional Committee and approval of the Basic and Production Engineering DivisionCouncil.This standard (Part 4) specifies basic rules for the development and application of central projection intechnical drawings. Other parts of this series are given as follows:IS 15021 (Part 1) :2001 Technical drawings — Projection methods: Part 1 SynopsisIS 15021 (Part 2) :2001 Technical drawings — Projection methods: Part 2 OrthographicrepresentationsIS 15021 (Part 3) :2001 Technical drawings — Projection methods: Part 3 AxonometricrepresentationsThe text of ISO Standard has been approved as suitable for publication as Indian Standard withoutdeviations. In the adopted standard certain terminology and conventions are not identical to thoseused in Indian Standards. Attention is particularly drawn to the following:a) Wherever the words ‘International Standard’ appear referring to this standard, they should beread as ‘Indian Standard’.b) Comma (,) has been used as a decimal marker, while in Indian Standards, the currentpractice is to use a full point (.) as the decimal marker.In this adopted standard, reference appears to the following International Standard for which IndianStandard also exists. The corresponding Indian Standard which is to be substituted in its place islisted below along with its degree of equivalence for the edition indicated :International Corresponding Degree ofStandard Indian Standard EquivalenceISO 10209-2:1993 IS 8930 (Part 2) :2001 Technical product Identicaldocumentation — Vocabulary: Part 2Terms relating to projection methodsThis adopted standard also gives Bibliography in Annex B which is informative. The correspondingIndian Standard against the ISO Standard is given below along with their degree of equivalence forthe editions indicated:/nternationa/ Corresponding Degree ofStandard Indian Standard EquivalenceISO 5456-1:1996 IS 15021 (Part 1) : 2001 Technical Identicaldrawings — Projection methods: Part 1SynopsisISO 5456-2:1996 IS 15021 (Part 2) : 2001 Technical dodrawings — Projection methods: Part 2Orthographic representationsISO 5456-3:1996 IS 15021 (Part 3) : 2001 Technical dodrawings — Projection methods: Part 3Axonometric representationsISO 10209-1:1992 IS 8930 (Part 1) :1995 Technical product dodocumentation — Vocabulary: Part 1Terms relating to technical drawings:General and types of drawings (firstrevision)IS 15021 ( Part 4 ) :2001ISO 5456-4:1996Indian StandardTECHNICAL DRAWINGS — PROJECTION METHODSPART4 CENTRAL PROJECTION1 ScopeThis part of 1S05456 specifies basic rules for thedevelopment and application of central projection intechnical drawings.2 Normative referenceThe following standard contains provisions which,through reference in this text, constitute provisions ofthis part of ISO 5456, At the time of publication, theedition indicated was valid. All standards are subjectto revision, and parties to agreements based on thispart of ISO 5456 are encouraged to investigate thepossibility of applying the most recent edition of thestandard indicated below. Members of IEC and ISOmaintain registers of currently valid internationalStandards.ISO 10209-2:1993, Technical product documentation— Vocabulary — Part 2: Terms relating to projectionmethods.3 DefinitionsFor the purposes of this part of ISO 5456, the defi-nitions given in ISO 10209-2 and the foHowing defi-nitions apply.3.1 alignment line Line parallel to a given linepassing through the projection centre. Its intersectionwith the projection plane gives the vanishing point ofall lines parallel to the given line.3.2 height of projection: Vertical distance of theprojection centre from the basid plane.3.3 horizontal distanca: Distance between theprojection centre and the projection plane.3.4 projection angle Angle formed by the projec-tion plane and the horizon plane.3.5 scale point Vanishing point of the horizontaldirection orthogonal to that bisecting the angle formedby the horizon line and the alignment line of the givenhorizontal line, and allowing the true length of theprojection of the given line to be determined.3.6 station of observation: Orthogonal projectionof the projection centre onto the basic plane.1.4IS 15021 ( Part 4 ) :2001ISO 5456-4:19964 SymbolsLetter symbols for terms used in central projectionare given in table 1 and illustrated in figures 1 and 2,as well as in the figures mentioned in table 1.Table 1— LattarsymbolsNo. Term Letter symbol Figura1) Projection plane T 11) Basic plane G 11) Basic line x 13.4 Projection angle P 51) Horizon plane HT 11) Horizon line h 13.1 Alignment line VI 41) Main point c 11) Vanishing point v 41) Main projector pL 11) Projection centre o 13.2 Height of projection H 13.3 Horizontal distance d 11) Vision cone K 21) Circle of vision Ks 31) Vision angle a 21) Projector PI 31) Distance point DP 133.5 Scale point MP 143.6 Station of observation Sp 11) Terms already defined in ISO 10209-2.5 CentralprojectionmethodsThe mode of the central projection depends on theposition of the object to be represented with respectto the projection plane.For possible positions and applicable projectionmethods, see 5.1 to 5.4.5.1 One-pointmethodA one-point projection method is a central projectionof an object having its principal face parallel to theprojection plane (special position). All parallel outlinesand edges of the object which are parallel to theprojection plane retain their direction in this represen-‘b.,. f.tation (horizontal lines remain horizontal and vertical ,?;90”, 3tha vanishing point for vertical lines is situated belowthe horizon line (see figure 5 and 7.5.1 and 7.5.2).5.4 CoordinatemethodRepresentation by the coordinate method is based onsimple proportions.The coordinates, related to the main projector of allrelevant points of the object to be represented, aretaken by the graphic method from the basic plane andelevation. From these point coordinates, the imagecoordinates are obtained by a calculation method andentered to scale. The image points are connected toeach other to provide a clear representation of theobject (see figure 6).6 Principle6.1 LocationandpositionoftheprojectionplaneThe image size of an object can be varied by parallelshifting of the projection plane. If the object is placedin front of the projection plane, the representation willbe enlarged. The object behind the projection planewill result in a smaller image. Figure 7 shows thechange in image size depending on the position of theobject with respect to the projection plane.Figure 8 shows the change in image size dependingon the method of representation with vertical orinclined projection planes. /3 is the included anglebetween the projection plane and the basic plane nearthe projection centre.2IS 15021 ( Part 4 ) :2001ISO 54564:1996Figure1— Projectionmodal of the centralprojectionIS 15021 ( Part4 ) :2001ISO 5456-4:1996xFigure2 — Wion coneand viaionanglein the projectionmodal of the centralprojectionIJ%c900Figure7 — Locationof projectionplanes Figure8 — Positionof projectionplanesIS 15021 ( Part 4 ) :2001ISO 5456-4: 19966.2 Circle of vision and vision cone instructive since length, width and height do notmatch the object’s inherent proportions (see figure 9).To obtain a fully instructive image of an object withoutperipheral distortions on the projection plane, the An object can be depicted nearly undistorted if theobject must be positioned within a vision cone having projectors result in a bundle of rays inclined not morean aperture angle not greater than 60°. than 30° with respect to the main projector. At thisHeavy peripheral distortions occur on images outside aperture angle the vision cone provides only a smallthe circle of vision; the image does not appear fully distortion on the projection plane./4To Tf!!u!iho‘\. “’b “ ““’””:,,!$paim#:: ::J[ +C I“-“-lW ‘—,1 ““~@@RI ISpFigure9 — Object, framed in a cube,within and outsidethe circleof vision8The main projector should hit the object to be de-picted in a part which is visually important, so that theobject is contained within the minimum vision cone.6.3 DistanceDifferent relative distances influence the image size andits appearance. When the distance between the objectand the projection plane is fixed and the projection centreand the object lie on opposite sides of the projectionplane, increasing the distance (d) between the projectioncentre and the projection plane gives enlarged andflattened representations. When the distance (d) is fixedand the object and the projection centre lie on oppositesides of the projection plane, increasing the distanceIS 15021 ( Part 4 ) :2001 --qISO 5456-4:1996{i,,t$1:$between the object and the projection plane gives rc+duced and flattened representations.,7 Principlesand methods of depiction17.1 Piercing method {f,,,Using the piercing method, the piercing points ofprojectors with the projection plane are shown bybasic plane and elevation, and may be determinedeither by drawing or by calculation (see figure 10).The piercing method allows even complex objects(round shapes, helicoids, etc.) to be easily repre-sented in central projection.h. .Figure10— projectionmodalturned intothe drawingsurfacewith sideview9IS 15021 ( Part 4 ) :2001ISO 5456-4:19967.2 Trace point — vanishing point methodsWith the trace point — vanishing point methods, theoutlines and edges of the object to be depicted areimaged from basic plane and elevation.7.2.1 Tracepoint— vanishingpoint method A(special position of the object)In method A, one vertical face of the object is parallelto the vertical projection plane (special position of theobject with respect to the projection plane), so thatthe vanishing point for those edges parallel to theprojection plane is situated at infinity and the vanish-ing point for those edges perpendicular to the projec-tion plane is the main point (see figure 11).7.2.2 Tracepoint — vanishingpoint method B(particular position of the object)In method B, horizontal faces of the object are per-pendicular to the vertical projection plane (particularposition of the object with respect to the projectionplane) so that the lines are represented by their traceon the projection plane and by their vanishing point(see figure 12).I :---~.1(c Mz ,,$a/ /1;‘G ,x ; ,--“” 1’T.-_ ——____— _ _,~--_ f_--f_;--./.f_;m=1P1 u/2Sp,Figure11— Object,framed in a cube(indicatedby a double-dashedline),in specialpositionwith respectto the projectionplaneaccordingto method A10IS 15021 ( Part 4 ) :2001ISO 5456-4:1996I?’jZ$,:, 90° to be depicted moves below the horizon line frominfinite to finite, so that tilting projected vertical linesDue to the inclination away from the projection cen- provide an optical distortion suggesting a taperingtre, the vanishing point for vertical lines of the object form (see figure 16).P-1v \v, \\J\Sp3c“--------/\/./l-h v 0//‘\,-/.”v’$2’//—Figure16— Object,framed in a cube (indicatedby a double-dashedline),in front of a projectionplaneinclinedaway from the projectioncentre15IS 15021 ( Part4 ) :2001ISO 5456-4:19967.6 Coordinate piercing methodThe coordinate piercing method is based on simpleproportions, in which each piercing point of the pro-jectors in the projection plane is not established bydrawing, but by calculation. This method is based ondividing the space in four quadrants by two referenceplanes, one horizontal and one vertical, each perpen-dicular to the projection plane, their common linebeing the main projector. The common lines of thehorizontal and vertical reference planes and the pro-jection plane are the X and Y axes of a rectangularCartesian coordinate system situated in the projectionplane, the origin of which is the main point. Theprojector ~ is positive (negative)when Al is above (below) the main projector.8 Developmentof a centralprojectionBy turning the basic plane into the projection plane(see figure 1), it is possible to present the represen-tation of the basic plane on the drawing surface andsubsequently to create the complete representationof the dimensions taken from the elevation.There are two different ways to turn the basic plane:.“.Figure17— Coordinatepiercingmethod16IS 15021 ( Part4 ) :2001ISO 5456-4:19968.1 Turning the basic plane downwards 8.2 Turning the projection plane downwardsThe station of observation, (Sp), is placed at thedistance d from C’, below the basic line (X). The The basic line becomes the axis of symmetry. Thisfrequently-used arrangement saves space on therepresentation is above, and the basic plane is below drawing surface and is called economy arrangementthe basic line; they do not cover each other. This (see figure 19).arrangement is cal!ed regular arrangement and givesthe best survey, but requires considerable space onthe drawing surface (see figure 18).$,,L-,xi“1’’__t’x\lPL’P1\ 6i”Ks,—_– ------ ——— ——_________ ____lIiI!iiiia -!ch -+,1J- -- ------ ---------- __ -;---- -————— —1Y/z-.-l-eQ/2SpFigure18— Regulararrangement(the representation is placed above the basic line X)-Figure19— Economyarrangement(the perspective representation is placed below the basic line X)17aIS 15021 ( Part 4 ) :2001ISO 5456-4: 1996Annex A(informative)Examples for comparison of different depiction methodsThe following figures A.1 to A.17 illustrate some of the different depiction meth