From 2a5e89fa97136967cca89b058bfee2cd16483865 Mon Sep 17 00:00:00 2001
From: bovlb <31326650+bovlb@users.noreply.github.com>
Date: Tue, 13 Dec 2022 22:27:43 -0800
Subject: [PATCH] [apriltag] Improve description of pose coordinates (NFC)
 (#4810)

The "bottom-left" language appears to be based on [a 2-D diagram  on another page](https://docs.wpilib.org/en/stable/docs/software/advanced-controls/geometry/coordinate-systems.html) and doesn't seem very helpful here.
---
 .../edu/wpi/first/apriltag/AprilTagFieldLayout.java   |  9 ++++-----
 .../native/include/frc/apriltag/AprilTagFieldLayout.h | 11 ++++-------
 2 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/apriltag/src/main/java/edu/wpi/first/apriltag/AprilTagFieldLayout.java b/apriltag/src/main/java/edu/wpi/first/apriltag/AprilTagFieldLayout.java
index 145411507d..6921b0b75c 100644
--- a/apriltag/src/main/java/edu/wpi/first/apriltag/AprilTagFieldLayout.java
+++ b/apriltag/src/main/java/edu/wpi/first/apriltag/AprilTagFieldLayout.java
@@ -33,11 +33,10 @@ import java.util.Optional;
  * meters with "width" and "length" values. This is to account for arbitrary field sizes when
  * transforming the poses.
  *
- * <p>Pose3ds are assumed to be measured from the bottom-left corner of the field, when the blue
- * alliance is at the left. By default, Pose3ds will be returned as declared when calling {@link
- * AprilTagFieldLayout#getTagPose(int)}. {@link #setOrigin(OriginPosition)} can be used to transform
- * the poses returned from {@link AprilTagFieldLayout#getTagPose(int)} to be correct relative to a
- * different coordinate frame.
+ * <p>Pose3ds in the JSON are measured using the normal FRC coordinate system, NWU with the origin
+ * at the bottom-right corner of the blue alliance wall. {@link #setOrigin(OriginPosition)} can be
+ * used to change the poses returned from {@link AprilTagFieldLayout#getTagPose(int)} to be from the
+ * perspective of a specific alliance.
  */
 @JsonIgnoreProperties(ignoreUnknown = true)
 @JsonAutoDetect(getterVisibility = JsonAutoDetect.Visibility.NONE)
diff --git a/apriltag/src/main/native/include/frc/apriltag/AprilTagFieldLayout.h b/apriltag/src/main/native/include/frc/apriltag/AprilTagFieldLayout.h
index 8f1c296a01..c69e4291af 100644
--- a/apriltag/src/main/native/include/frc/apriltag/AprilTagFieldLayout.h
+++ b/apriltag/src/main/native/include/frc/apriltag/AprilTagFieldLayout.h
@@ -31,13 +31,10 @@ namespace frc {
  * "width" and "length" values.  This is to account for arbitrary field sizes
  * when transforming the poses.
  *
- * Pose3ds are assumed to be measured from the bottom-left corner of the field,
- * when the blue alliance is at the left. By default, Pose3ds will be returned
- * as declared when calling GetTagPose(int).
- * SetOrigin(AprilTagFieldLayout::OriginPosition) can be used to transform the
- * poses returned by GetTagPose(int) to be correct relative to a different
- * coordinate frame.
- */
+ * Pose3ds in the JSON are measured using the normal FRC coordinate system, NWU
+ * with the origin at the bottom-right corner of the blue alliance wall.
+ * SetOrigin(OriginPosition) can be used to change the poses returned from
+ * GetTagPose(int) to be from the perspective of a specific alliance. */
 class WPILIB_DLLEXPORT AprilTagFieldLayout {
  public:
   enum class OriginPosition {