openrelief
==========

This software is an independent, open-source implementation of a terrain
visualization technique that combines topographic slope with positive and
negative topographic openness, rendered as a red-shaded relief image. The
technique is commonly known as the "Red Relief Image Map" (RRIM).

Attribution
-----------
The red-relief image map method was developed by Tatsuro Chiba, Shin-ichi
Kaneta and Yusuke Suzuki at Asia Air Survey Co., Ltd. The topographic openness
measure it builds on was introduced by Ryuzo Yokoyama, Michio Shirasawa and
Richard J. Pike. This package reimplements those published methods from the
academic literature; it is not produced, endorsed by, or affiliated with Asia
Air Survey Co., Ltd.

Trademarks
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"RRIM", "Red Relief Image Map", and "赤色立体地図" are used or claimed as
trademarks of Asia Air Survey Co., Ltd. Those names are referenced here only to
describe the method this software implements (nominative use). This package is
deliberately named "openrelief" and does not use those marks as its product
name or branding. Do not market derivatives of this software under those marks.

Intellectual-property note
--------------------------
The RRIM method was patented by Asia Air Survey Co., Ltd., with patent family
members filed in Japan, the United States, China and Taiwan (e.g. JP 3670274).
These patents derive from filings in the early 2000s and, based on the standard
~20-year patent term, the relevant patents appear to have expired. Patent
status is jurisdiction-specific and time-sensitive, and nothing here is legal
advice. Before publishing, redistributing, or building a commercial product on
this software, independently verify the current legal status of the relevant
patents in every jurisdiction that matters to you (e.g. J-PlatPat for Japan,
the USPTO / Google Patents for the United States), and consult a qualified
intellectual-property attorney if anything material depends on it.

Citation
--------
If you use this software in academic work, please cite the original methods:

  Chiba, T., Kaneta, S., & Suzuki, Y. (2008). Red relief image map: new
  visualization method for three-dimensional data. International Archives of
  the Photogrammetry, Remote Sensing and Spatial Information Sciences,
  XXXVII(B2), 1071-1076.

  Yokoyama, R., Shirasawa, M., & Pike, R. J. (2002). Visualizing topography by
  openness: a new application of image processing to digital elevation models.
  Photogrammetric Engineering & Remote Sensing, 68(3), 257-265.
