Use custom anchors for url references

Author: cmacfarl

docs/source/apriltag/vision_portal/apriltag_localization/apriltag-localization.rst

@@ -237,8 +237,8 @@ Reference Frames
 
 In the above example. the yaw angle is given as (approximately) -90 degrees.
 But the camera is facing in the negative X direction, thus has a heading or yaw
-angle of -180 degrees in the official FTC `field coordinate system
-<https://ftc-docs.firstinspires.org/en/latest/game_specific_resources/field_coordinate_system/field-coordinate-system.html>`_
+angle of -180 degrees in the official FTC 
+:ref:`field coordinate system <first field coordinate system>`
 :
 
 .. figure:: images/50-field-axes.png
@@ -250,8 +250,7 @@ angle of -180 degrees in the official FTC `field coordinate system
 
 This sample OpMode uses a reference frame (coordinate system) that may be
 different than what you expect from other FTC navigation applications,
-including `IMU or robot axes
-<https://ftc-docs.firstinspires.org/en/latest/programming_resources/imu/imu.html?highlight=field%20coordinates#axes-definition>`_\
+including :ref:`IMU or robot axes <imu axes def>`
 , odometry device axes, and the FTC field system (shown above).  These
 differences typically result in basic and obvious changes in axis direction,
 axis swapping, and orthogonal angles (90-degree increments).

docs/source/apriltag/vision_portal/apriltag_reference_frame/apriltag-reference-frame.rst

@@ -96,7 +96,7 @@ Related Info
 
 More discussion of the AprilTag reference frame is available here:
 
-- https://ftc-docs.firstinspires.org/apriltag-detection-values
+:ref:`Understanding AprilTag Detection Values <apriltag/understanding_apriltag_detection_values/understanding-apriltag-detection-values:understanding apriltag detection values>`
 
 This section described the SDK's default AprilTag reference frame.  Teams are
 welcome to make other calculations, such as the pose of the camera (or robot)

docs/source/game_specific_resources/field_coordinate_system/field-coordinate-system.rst

@@ -1,3 +1,5 @@
+.. _first field coordinate system:
+
 *FIRST* Tech Challenge Field “Coordinate System" Definition
 ===========================================================
 

docs/source/programming_resources/imu/imu.rst

@@ -159,6 +159,8 @@ re-open that OpMode to capture this updated configuration. Blocks are provided
 only for devices in the configuration that’s active*\  **upon opening**\  *an
 OpMode.*
 
+.. _imu axes def:
+
 Axes Definition
 ---------------