Overview
EN ISO 25178-72:2017 (ISO 25178-72:2017) specifies the x3p XML file format for storage and exchange of surface topography and profile data. Published by CEN/ISO as part of the ISO 25178 series on geometrical product specifications (GPS) - surface texture: areal - this standard defines a portable, interoperable container for areal surface measurements used in metrology, research and industry.
Key topics and technical requirements
- File structure and extension: x3p files are ZIP-based containers with a defined minimum set of contents; the recommended file extension is .x3p.
- main.xml record layout: the standard describes core records (for example, header/axes definitions, metadata, 3D point data, checksum) that must appear in main.xml inside the container.
- Data types and encodings: supported numeric types (int16, int32, float32, float64), IEEE-754 floating-point handling (including NaN), and binary-encoded coordinate options.
- Optional elements: validity masks, vendor-specific extensions and binary coordinate encodings are defined as optional parts of the container.
- Integrity and checksums: md5 checksum support for file integrity verification is specified.
- Units and offsets: requirements for units and recommended offset values to ensure consistent interpretation of coordinates and measurements.
- Normative references and alignment: ties to other GPS/metrology standards (for example ISO 25178-600) and GPS decision rules (ISO 8015, ISO 14253-1) are indicated.
- Informative annexes: sample main.xml, XML format guidance and relations to GPS matrix models are included to aid implementation.
Practical applications and typical users
- Who uses it: metrology laboratories, surface-measurement instrument manufacturers, software vendors (data capture and analysis), research institutions, and quality-control engineers.
- Typical use cases: exchange of areal topography datasets between measurement instruments and analysis software; archiving of surface measurement results; interoperability in multi-vendor measurement workflows; research data sharing and reproducible surface characterization.
- Benefits: standardized, vendor-neutral format reduces proprietary fragmentation, improves data portability, and supports automated processing and long-term data preservation.
Related standards
Keywords: ISO 25178-72, EN ISO 25178-72:2017, x3p, XML file format, surface texture, areal topography, metrology, topography data exchange, GPS standard.