Developing reliably distinguishable color schemes for legends of natural resource taxonomy-based maps

ABSTRACT

The legends of natural resource taxonomy-based maps (e.g. soil, geological, geomorphological, vegetation, and land cover/land use) need many different distinguishable colors. The existing methods of color selection for map legends are based on the designer subjectivity, ensuring schemes having few colors. An analysis of the modeling and management of colors in digital applications has led to define an algorithm to calculate an objective colorimetric measure of color difference – “DE*_ab” – based on the perceptually uniform color model CIELAB. The proposed method consists of a set of specific rules for developing hierarchically structured color schemes and a specific procedure for ensuring selection of a large number of reliably distinguishable colors, based on a color difference threshold. The accuracy of color reproduction in printing processes is also taken into account. The method has been applied to develop a standard of colors for soil maps. It contains 63 colors and has been used for developing a soil map having 41 standard colors. A user test of the method results proved that thresholds of 10 DE*_ab units and 15 DE*_ab units ensure obtaining acceptably distinguishable colors for displaying/printing maps by using high-quality, respectively, current devices. Three datasets that support the research are given.

KEYWORDS:

• Natural resource
• taxonomy-based map
• map color selection
• map color scheme
• map readability
• reliably distinguishable color difference
• soil map color legend
• Romania

Acknowledgments

Authors thank soil specialists, particularly prof. N. Florea and D.M. Motelica, for their support in testing the Standard of colors and the Dominant Soil Map of Romania at the 1:700,000 scale. Authors express special thanks to the anonymous reviewers, particularly to the editor, prof. Nicholas Chrisman, for their suggestions, which much improved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are openly available in Figshare at the links: https://doi.org/10.6084/m9.figshare.12782105, https://doi.org/10.6084/m9.figshare.12782138, https://doi.org/10.6084/m9.figshare.14331299

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Short explanations of our procedure for obtaining the symbol textures 630 - 660

We use ArcMap 10.5

We built up the four symbol textures as follows:

Table

Additional information

Funding

This research was partly supported by the Romanian Ministry of Research and Innovation under Grant number PN-19.34.01.01.