Fabio Crameri
batlow: A Scientific colour map
Scientific colour maps

Cyclic colour maps

  • Perceptually uniform  ✔︎
  • Perceptually ordered ✔︎
  • Colour-vision-deficiency friendly ✔︎ 
  • Readable as black-and-white print ✔︎
  • Provided in all major formats ✔︎
  • Cyclic / Orbitual

  • No black

  • Use with circular data only!

Cyclic (or orbital) colour maps are colour gradients that have neither a beginning nor an end. They are useful to display periodic data sets like angular data or data from Synthetic Aperture Radar (SAR) interferometry, which is used to display Earth’s surface displacement (see below, for example). The cyclic Scientific colour maps, like romaO, are diverging colour maps with matching ends. Since this class has no beginning or end, it is very versatile and does not have to be carefully adjusted to the underlying data.
  • Designed for periodic data sets

romaO

Colour map diagnostics


 The figure shows the colour map with low gradient ripples to indicate how it represents low-contrast regions in different locations of the colorbar, and a plot of the lightness difference, dE, indicating better perceptual-uniformity the flatter the curve.

→ Compare to the diagnostics of the rainbow (a.k.a. jet) colour map.

Diagnostics performed after Kovesi, P. (2015), Good colour maps: How to design them, CoRR, abs/1509.03700 and based on MatLab scripts from Peter Kovesi.

Read more about it here.

In-use example

Remote sensing

Figure. Better data representation in Remote Sensing Science. The surface uplift over a given time period on the Darwin volcano (Galápagos Islands, Ecuador; example data set from Jónsson, 2002) presented with (a) the unscientific jet and (b) the scientifically-derived cyclic romaO colour map. The Scientific colour map prevents the sharp boundary between maximum and minimum values and other visual data distortion, and makes the figure intuitively and universally readable.

Figure from Crameri et al., 2020, Nature Communications, Supplementary material.