From 5605b49907ad7e5c84c08ce416941f92f418c7db Mon Sep 17 00:00:00 2001
From: Austin Sanders <arsanders@usgs.gov>
Date: Fri, 15 Nov 2024 11:22:56 -0700
Subject: [PATCH] Update quaternions to prevent sign flipping (#623)
* Updated quaternion accessor to prevent unwanted sign flip
* Updated changelog
* flipped quaternion signs to follow new logic
---------
Co-authored-by: Sanders <arsanders@igswza281l2314.gs.doi.net>
---
CHANGELOG.md | 1 +
ale/rotation.py | 22 +++++++++++++++++++++-
tests/pytests/data/isds/dawnvir_isd.json | 8 ++++----
3 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 58a7bf4..dc3d7d7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -58,6 +58,7 @@ release.
- Fixed incorrect distortion look up in Orex camera when working with PolyCam images [#583](https://github.com/DOI-USGS/ale/pull/583)
- Brought timing in line with ISIS for the KaguyaMiIsisLabelNaifSpiceDriver [#599](https://github.com/DOI-USGS/ale/pull/599)
- Brought timing in line with ISIS for the MroMarciIsisLabelNaifSpiceDriver [#600](https://github.com/DOI-USGS/ale/pull/600)
+- Fixed a bug in which quaternions would flip sign in a way that caused interpolation errors [#603](https://github.com/DOI-USGS/ale/issues/603)
## [0.10.0] - 2024-01-08
diff --git a/ale/rotation.py b/ale/rotation.py
index aa603d6..eaded57 100644
--- a/ale/rotation.py
+++ b/ale/rotation.py
@@ -196,7 +196,27 @@ class TimeDependentRotation:
the destination reference frame. The quaternions are in scalar
last format (x, y, z, w).
"""
- return self._rots.as_quat()
+ quats = self._rots.as_quat()
+
+ # First find the largest magnitude quaternion coefficient and its coordinate
+ num_quats = len(quats)
+ max_q = 0.0
+ max_j = 0
+ for i in range(num_quats):
+ for j in range(4):
+ if abs(quats[i][j]) > abs(max_q):
+ max_q = quats[i][j]
+ max_j = j
+
+ # Ensure the signs are consistent
+ qcnt = 0
+ for i in range(num_quats):
+ if quats[i][max_j] * max_q < 0:
+ qcnt = qcnt + 1
+ for j in range(4):
+ quats[i][j] *= -1.0
+
+ return quats
@quats.setter
def quats(self, new_quats):
diff --git a/tests/pytests/data/isds/dawnvir_isd.json b/tests/pytests/data/isds/dawnvir_isd.json
index 90674bb..01c3df4 100644
--- a/tests/pytests/data/isds/dawnvir_isd.json
+++ b/tests/pytests/data/isds/dawnvir_isd.json
@@ -339,10 +339,10 @@
],
"quaternions": [
[
- -0.08339426680875163,
- 0.2825790922154143,
- -0.2899354389711647,
- 0.9105667982826637
+ 0.08339426680875163,
+ -0.2825790922154143,
+ 0.2899354389711647,
+ -0.9105667982826637
],
[
-0.05753008804150366,
--
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