1、Designation: E2807 11Standard Specification for3D Imaging Data Exchange, Version 1.01This standard is issued under the fixed designation E2807; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in
2、parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification describes a data file exchange formatfor three-dimensional (3D) imaging data, known as the ASTME57 3D file format, Version 1.0
3、. The term “E57 file” will beused as shorthand for “ASTM E57 3D file format” hereafter.1.2 An E57 file is capable of storing 3D point data, such asthat produced by a 3D imaging system, attributes associatedwith 3D point data, such as color or intensity, and 2D imagery,such as digital photographs obt
4、ained by a 3D imaging system.Furthermore, the standard defines an extension mechanism toaddress future aspects of 3D imaging.1.3 This specification describes all data that will be stored inthe file. The file is a combination of binary and eXtensibleMarkup Language (XML) formats and is fully document
5、ed inthis specification.1.4 All quantities standardized in this specification areexpressed in terms of SI units. No other units of measurementare included in this standard.1.4.1 DiscussionPlanar angles are specified in radians,which are considered a supplementary SI unit.1.5 This standard does not p
6、urport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.6 This standard does not purport to addre
7、ss legal con-cerns, if any, associated with its use. It is the responsibility ofthe user of this standard to comply with appropriate regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standard:2E2544 Terminology for Three-Dimensional (3D) ImagingSystems2.2 IEEE Standard:3754-1985 IEE
8、E Standard for Binary Floating-Point Arith-metic2.3 IETF Standard:4RFC 3720 Internet Small Computer Systems Interface(iSCSI)2.4 W3C Standard:5XML Schema Part 2: Datatypes Second Edition3. Terminology3.1 DefinitionsTerminology used in this specificationconforms to the definitions included in Terminol
9、ogy E2544.3.2 Definitions of Terms Specific to This Standard:3.2.1 backward compatibility, nability of a file reader tounderstand a file created by a writer of an older version of a fileformat standard.3.2.2 byte, ngrouping of 8 bits, also known as an octet.3.2.3 camel case, nnaming convention in wh
10、ich com-pound words are joined without spaces with each words initialletter capitalized within the component and the first letter iseither upper or lowercase.3.2.4 camera image, nregular, rectangular grid of valuesthat stores data from a 2D imaging system, such as a camera.3.2.5 camera projection mo
11、del, nmathematical formulaused to convert between 3D coordinates and pixels in a cameraimage.3.2.6 file offset, nsee physical file offset.3.2.7 file-level coordinate system, ncoordinate systemcommon to all 2D and 3D data sets in a given E57 file.3.2.8 forward compatibility, nability of a file reader
12、 toread a file that conforms to a newer version of a formatspecification than it was designed to read, specifically havingthe capability to understand those aspects of the file that weredefined in the version it was designed to read, while ignoringthose portions that were defined in later versions o
13、f the formatspecification.1This specification is under the jurisdiction of ASTM Committee E57 on 3DImaging Systems and is the direct responsibility of Subcommittee E57.04 on DataInteroperability.Current edition approved Feb. 1, 2011. Published March 2011.2For referenced ASTM standards, visit the AST
14、M website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3For referenced IEEE standards, visit http:/grouper.ieee.org/groups/754.4For referenced Internet Engineeri
15、ng Task Force (IETF) standards, visit theIETF website, www.ietf.org.5String representations (the lexical space) of the numeric datatypes are docu-mented in the W3C standard: “XML Schema Part 2: Datatypes Second Edition”,available on the website http:/www.w3.org/TR/xmlschema-2/.1Copyright ASTM Intern
16、ational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.9 logical length, nnumber of bytes used to describesome entity in an E57 file, not including CRC checksum bytes.3.2.10 physical file offset, nnumber of bytes preceding thespecified byte location in an E5
17、7 file, counting payload bytesand checksums.3.2.10.1 DiscussionThis term is also known as the fileoffset.3.2.11 physical length, nnumber of bytes used to describesome entity in an E57 file, including CRC checksum bytes.3.2.12 record, nsingle collection in a sequence ofidentically-typed collections o
18、f elements.3.2.13 rigid body transform, ntype of coordinate trans-form that preserves distances between all pairs of points thatfurthermore does not admit a reflection.3.2.13.1 DiscussionA rigid body transform can be used,for example, to convert points from the local coordinates of a3D data set (for
19、 example, a single laser scan) to a commoncoordinate system shared by multiple 3D data sets (for ex-ample, a set of laser scans).3.2.14 XML namespace, nmethod for qualifying elementnames in XML to prevent the ambiguity of multiple elementswith the same name.3.2.14.1 DiscussionXML namespaces are used
20、 in an E57file to support the definition of extensions.3.2.15 XML whitespace, nsequence of one or more of thefollowing Unicode characters: the space character (20 hexa-decimal), the carriage return (0D hexadecimal), line feed (0Ahexadecimal), or tab (09 hexadecimal).3.2.16 zero padding, none or more
21、 zero-valued bytesappended to the end of a sequence of bytes.4. Acronyms4.1 ASCIIAmerican Standard Code for Information Inter-change4.2 CRCCyclic redundancy check4.3 GUIDGlobally unique identifier4.4 IEEEInstitute of Electrical and Electronics Engineers4.5 IETFInternet Engineering Task Force4.6 iSCS
22、IInternet small computer system interface4.7 JPEGJoint Photographic Experts Group4.8 PNGPortable network graphics4.9 URIUniform resource identifier4.10 UTCCoordinated universal time4.11 UTFUnicode Transformation Format4.12 W3CWorldWide Web Consortium4.13 XMLeXtensible Markup Language5. Notation and
23、Mathematical Concepts5.1 The following notation and established mathematicalconcepts are used in this specification.5.2 Intervals:5.2.1 A closed interval is denoted a, b, where a # b.Aclosed interval includes the endpoints a and b and all numbersin between.An open interval is denoted (a, b), where a
24、#b.Anopen interval includes the numbers between the endpoints aand b, but does not include the endpoints themselves. Thehalf-open intervals (a, b and a, b) do not include the a and bendpoints, respectively.5.3 Cartesian Coordinate System:5.3.1 Points in Cartesian coordinates are represented by anord
25、ered triplet (x, y, z), where x, y and z are coordinates alongthe X, Y, and Z axes, respectively. The coordinate system isright-handed.5.4 Cylindrical Coordinate System:5.4.1 Points in cylindrical coordinates are represented by anordered triplet (r, u, z), where r is the radial distance (inmeters),
26、u is the azimuth angle (in radians), and z is the height(in meters).5.4.1.1 The azimuth angle is measured as the counterclock-wise rotation of the positive X-axis about the positive Z-axis ofa Cartesian reference frame.5.4.2 The following restrictions on cylindrical coordinatesare applied:r $0 (1)p,
27、u# p (2)5.4.3 The conversion from Cartesian to cylindrical coordi-nates is accomplished through the formulas (note that the zcoordinate is the same in both systems):r5=x21 y2! (3)u5atan2y,x! (4)5.4.3.1 The function “atan2(y, x)” is defined as the functionreturning the arc tangent of y/x, in the rang
28、e (p,+p radians.The signs of the arguments are used to determine the quadrantof the result.5.4.3.2 In degenerate cases, the following convention isobserved:If x = y = 0, then u =0.5.4.4 Conversely, cylindrical coordinates can be convertedto Cartesian coordinates using the formulas:x 5rcosu! (5)y 5rs
29、inu! (6)5.5 Spherical Coordinate System:5.5.1 Points in spherical coordinates are represented by anordered triplet (r, u, f), where r is the range (in meters), u isthe azimuth angle (in radians), and f is the elevation angle (inradians).5.5.2 The following restrictions on spherical coordinates areap
30、plied:r$0 (7)p,u# p (8)p2# f #p2(9)5.5.3 The conversion from spherical to Cartesian coordi-nates is accomplished through the formulas:x 5 r cosf!cosu! (10)y 5 r cosf!sinu! (11)z 5 r sinf! (12)5.5.4 Conversely, in non-degenerate cases, Cartesian coor-dinates can be converted to spherical coordinates
31、via theformulas:r 5 =x21 y21 z2! (13)u5atan2y,x! (14)E2807 112f5arcsinSzrD(15)5.5.4.1 In degenerate cases, the following conventions areobserved:If x = y = 0, then u =0;If x = y = z = 0, then both u = 0 and f =0.5.5.5 DiscussionThe elevation is measured with respectto the XY-plane, with positive ele
32、vations towards the positiveZ-axis. The azimuth is measured as the counterclockwiserotation of the positive X-axis about the positive Z-axis. Thisdefinition of azimuth follows typical engineering usage. Notethat this differs from traditional use in navigation or surveying.5.6 Quaternions:5.6.1 A qua
33、ternion is a generalized complex number. Aquaternion, q, is represented by an ordered four-tuple (w,x,y,z),where q = w + xi + yj + zk. The coordinate w defines the scalarpart of the quaternion, and the coordinates (x, y, z) define thevector part.5.6.2 The norm of a quaternion, | q |, is defined as:|
34、 q | = =w21 x21 y21 z2.5.6.3 A unit quaternion, q, has the further restriction that itsnorm | q |=1.5.6.4 Rotation of a point p by a unit quaternion q is given bythe matrix formula:p8 5 Rp (16)where:R 5Fw21 x2 y2 z22xy 1 wz!2xz wy!2xy wz!w21 y2 x2 z22yz 1 wx!2xz 1 wy!2yz wx!w21 z2 x2 y2G(17)5.6.5 Di
35、scussionUnit quaternions are used in this stan-dard to represent rotations in rigid body transforms.5.7 Rigid Body Transforms:5.7.1 A rigid body transform converts points from onecoordinate reference frame to another, preserving distancesbetween pairs of points and, furthermore, not admitting arefle
36、ction. A rigid body transform can be represented as a3 3 3 rotation matrix R and a translation 3-vector t.5.7.2 A 3D point is transformed from the source coordinatesystem to the destination coordinate system by first applyingthe rotation and then the translation. More formally, thetransformation ope
37、ration T(.) of a point p is defined as:p8 5 Tp! 5 Rp 1 t (18)The rotation matrix R can be computed from a unit quater-nion q using Eq 17.5.7.3 DiscussionRigid body transforms are used in thisstandard to support the transformation of data represented in alocal coordinate system, such as the coordinat
38、e system of asensor used to acquire a 3D data set, to a common file-levelcoordinate system shared by all 3D data sets.5.8 Trees:5.8.1 A tree is data structure that represents an acyclicgraph. A tree consists of nodes, which store some information,and edges (also known as arcs) that connect the nodes
39、. Thesingle topmost node is called the root node. A node may havezero or more nodes connected below it, which are called childnodes. Each node, except the root node, has exactly one nodeconnected above it, which is called the parent node. Nodes withno children are called leaf nodes. A descendant is
40、a direct orindirect child of a given node.5.8.2 DiscussionTrees are used in this standard to de-scribe the structure of XML data, as well as index data inbinary sections.5.9 XML Elements and Attributes:5.9.1 An XML element is the fundamental building block ofan XML file. An element consists of a sta
41、rt tag, optionalattributes, optional child elements, optional child text, and anend tag. Element names in an E57 file are case sensitive.Element names in this specification are written in camel casewith a lowercase initial character. Type names in this specifi-cation are written in camel case with a
42、n upper case initialcharacter.5.9.2 DiscussionSee Fig. 1 for an excerpt of XML thatillustrates the parts of an XML element.5.9.3 XML elements that have child elements form a tree,with each element being a node.5.9.4 A pathname is a string that specifies the sequence ofelements names that are encount
43、ered when traversing from agiven origin element to a destination element in an XML tree.In this standard, pathnames are only defined for destinationelements that are descendants of the origin element. A relativepathname is formed by concatenating the sequence of elementnames traversed using the forw
44、ard slash (“/”) as a separator.Each successive element in the sequence shall be a child of theprevious element. Note that the element name of the originelement does not appear in the pathname. An absolute path-name has an origin that is the root element of the tree, and isformed by prepending a forw
45、ard slash to the relative pathname.5.9.5 DiscussionAs an example, consider a hypotheticalE57 file consisting of a root element named e57Root whichFIG. 1 XML Elements and AttributesE2807 113contains a child element named data3D, which contains achild element named 0, which contains a child element na
46、medpose, which contains a child element named translation,which contains a child element named x. Then the absolutepathname of the x element is “/data3D/0/pose/translation/x”, and the relative pathname of the xelement relative to the pose element is “translation/x”.6. General File Structure6.1 E57 f
47、iles shall use the filename extension “.e57” (notelowercase e).6.2 This specification defines a binary file format composedof a sequence of pages.6.2.1 Each page shall be composed of 1020 bytes of data(known as the payload) followed by a 32-bit cyclic redundancycheck (CRC) checksum computed on the p
48、receding payload.6.2.2 The length of an E57 file shall be an integral multipleof 1024 bytes. Any unused bytes in the payload of the finalpage in a file shall be filled with 0 values.6.2.3 The CRC checksum shall be computed on the 1020bytes of data using the iSCSI polynomial CRC32C (CRC32-bit Castagn
49、ioli) as documented in IETF RFC 3720, Section12.1 (http:/tools.ietf.org/html/rfc3720).6.2.4 DiscussionSequences of data without the CRCchecksum bytes are known as logical sequences, while se-quences of data with the CRC checksum bytes included areknown as physical sequences. All sequences of characters (inXML section) or bytes (in binary sections) described in thisstandard are logical sequences. The physical sequence repre-sentation of a logical sequence may have an interveningchecksum if the l
