SPIF - Single Particle Image Format

Motivation

Particle imaging probes have been used for many years to record the shapes and concentrations of airborne particles 1. A variety of file formats are used by the manufacturers of such instruments to transmit and store particle image data. The formats are/were designed around hardware and bandwidth limitations and so may not have a convenient or standard structure. This has meant that users must write their own routines for reading (often binary) image data files for processing and analysis. We propose a new file format for raw image data called the Single Particle Image Format (SPIF). The new format will specify a single structure which all imaging probe data formats may be translated into leading to improved accessibility for users and a refinement of (now common) data processing routines. It may be that this format could be adopted by instrument manufacturers so that all raw image data is immediately available in a standard format. The format is also suitable for the long-term archiving of raw data and so has the potential to satisfy usage requirements across the range of usage environments.

Optical Array Probe (OAP) images are created by triggering a 1-dimensional array of photodiodes on a nanosecond timescale to create a series of slices as a particle travels through the sample volume. These slices are used to construct a 2-dimensional image of the particle with a set width that corresponds to the number of photodiodes in the 1-dimensional array and a variable length that depends on the size and shape of the particle. Different types of imaging probes may use a 2-dimensional CCD or similar photodetector to create true 2-dimensional images of passing particles. The dimensions of the produced images may not have a fixed size, for example probes such as the SPEC 3V-CPI define a region of interest that is reduced to only contain the particle image in order to reduce data bandwidth requirements and file size.

SPIF files can contain both of these types of images which increases it’s flexibility and future-proofs the convention, more details are given in Image Array Structure.

Contents

• Structure
  • Mandatory and Optional Content
  • Instrument Channels
  • Image Array Structure
• SPIF File Definition
  • SPIF Root Attributes
  • Instrument Channel Group
• SPIF Extensions and Optional Extras
  • Auxillary Data Group
  • Level-0 Processed Data Group
  • Level-1 Processed Data Group
  • Diameter definitions
  • Level-2 Processed Data Group

Current Status

Project SPIF - Single Particle Image Format

Description SPIF convention definitions documentation

Project repository https://github.com/graemenott/SPIF

Project version 0.86

Python version 3.7

Created Long ago…

Modified May 06, 2021

1

Baumgardner, D., S. J. Abel, D. Axisa, R. Cotton, J. Crosier, P. Field, C. Gurganus, A. Heymsfield, A. Korolev, M. Krämer, P. Lawson, G. McFarquhar, Z. Ulanowski, and J. Um. “Cloud Ice Properties: In Situ Measurement Challenges”, Meteorological Monographs 58, 9.1-9.23, doi: 10.1175/AMSMONOGRAPHS-D-16-0011.1, 2017.