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Data Format and Meta Data

Measurement data is provided as raw data. Depending on the nature of the firearm identification approach, users may have to apply data processing operations such as data trimming, outlier rejection, edge detection, leveling, form removal, and filtering.

Reflectance microscopy images are provided in lossless .PNG format. 3D topography data are provided in .X3P format (XML 3D surface Profile):

  • Defined in ISO working draft 25178-72 for exchange of surface texture data
  • Open source read/write functions (C++ and Matlab™) and converters
  • Enables (custom) meta data defining measurement parameters
  • NIST is collaborating with industry partners for application to 3D forensic surface topography data
Each X3P file contains four records:
  • Record 1: Header, data types, and axes definition
  • Record 2: Meta data regarding the instrument and user
  • Record 3: Profile Data (x, y, z)
  • Record 4: Checksum of the xml-document
For more information regarding the X3P file format, please visit: http://open-gps.sourceforge.net/
As part of the Open Forensic Metrology Consortium (OpenFMC)Cadre Forensics and John Jay College of Criminal Justice provide software to read and write X3P into both Matlab™ and C++. OpenFMC is an informal collaboration of industry, academic, and government research laboratories.


Each measurement data file contained in the database will have a set of meta data describing the study, firearm, bullet/cartridge case, and measurement parameters. The meta data organization tree is shown below:

X3P Viewer

To download a free X3P viewer, please head to http://www.openfmc.org. At the bottom of the page, click on “Request Viewer”.

All studies will have a spreadsheet detailing the meta data. A description of each meta data field can be found in the Meta Data Specification. If you are planning to send test fires or measurement data for inclusion into the database, please use this spreadsheet to enter the meta data. (NBTRD Study Meta Data.xls)