pc2img — NOTICE
===============

pc2img is licensed under the BSD 3-Clause License (see the LICENSE file);
Copyright (c) 2022–2026 ETH Zurich, Institute of Geodesy and Photogrammetry,
Geosensors and Engineering Geodesy. This NOTICE records third-party attribution
and the intellectual-property basis for the RRIM feature that ships with pc2img.

RRIM feature — patent-expiry basis
----------------------------------

The RRIM feature (`src/pc2img/features/rrim.py`) is an independent, image-space
implementation of the red-relief-image visualization technique of Chiba et al.
(Asia Air Survey Co., Ltd.). It is NOT derived from, and does not copy, any Asia
Air Survey source code or product.

The core "Visualizing system, method, and program" patent family that claims the
technique — mapping terrain to a slope-reddened, openness-brightened 2-D image —
has EXPIRED in every jurisdiction in which it was granted:

    United States   US 7,764,282 B2   Expired (adjusted expiration 2025-10-05)
    Japan           JP 3670274        Expired
    China           CN 1711568B       Expired
    Taiwan          TW I285852        Expired

Because the core patent family has expired, the claimed invention has entered the
public domain on term expiry. It may be practiced and redistributed by anyone,
and NO license from Asia Air Survey is required to ship pc2img's RRIM feature.

(Note: the correct core US patent is US 7,764,282 B2. US 7,264,282 is an
unrelated patent and must not be cited here.)

Attribution
-----------

- The red-relief-image technique is credited to Tatsuro Chiba and Asia Air Survey
  Co., Ltd. (アジア航測株式会社), first priority date 2002-11-05.
- The topographic-openness measures used for the brightness component are the
  independent academic method of 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. Topographic openness is independent prior art and is
  not proprietary to Asia Air Survey.

Trademark disclaimer
--------------------

"RRIM" and "Red Relief Image Map" may be trademarks (RRIM®) of Asia Air Survey
Co., Ltd. A trademark is a distinct right that patent expiry does not release.
pc2img uses these terms descriptively (nominative use) to name an independent
implementation of the published red-relief technique of Chiba et al. pc2img is
NOT endorsed by, affiliated with, or sponsored by Asia Air Survey Co., Ltd., and
does not present itself as "RRIM®".

Full basis
----------

The full patent-status review, including the correct patent numbers, the
verbatim claim-1 non-infringement reads for the two still-active Asia Air Survey
patents (JP 5281518, US 11,836,856), and the openness prior-art citation, is
recorded in `docs/ip/rrim-ip-findings.md`. That document is a good-faith
engineering assessment and is not legal advice.
