<![CDATA[AprilTag Relocalization]]>https://forum.modalai.com/category/23RSS for NodeWed, 20 May 2026 20:19:53 GMTSun, 18 Jan 2026 16:44:22 GMT60<![CDATA[AprilTag relocalization fails with down-facing camera due to camera extrinsics mismatch (roll/pitch out of bounds)]]>@Eric-Katzfey
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system-image: 1.8.02-M0054-14.1a-perf
kernel: #1 SMP PREEMPT Mon Nov 11 22:47:44 UTC 2024 4.19.125
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hw platform: M0054
mach.var: 1.0.1
SKU: MRB-D0014-4-V1-C27-T9-M22-X0
────────────────────────────────────────────────────────────────────────────────
voxl-suite: 1.4.5
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Packages:

I am getting this issue as well, where I constantly get WARNING, apriltag roll/pitch out of bounds issue with the front or down tracking camera.

]]>https://forum.modalai.com/topic/4992/apriltag-relocalization-fails-with-down-facing-camera-due-to-camera-extrinsics-mismatch-roll-pitch-out-of-boundshttps://forum.modalai.com/topic/4992/apriltag-relocalization-fails-with-down-facing-camera-due-to-camera-extrinsics-mismatch-roll-pitch-out-of-boundsSun, 18 Jan 2026 16:44:22 GMT<![CDATA[Setting up different AprilTag families]]>Hey @dvz, thanks for your query

We’re currently in the process of updating the voxl-tag-detector to support additional AprilTag families beyond just the 36h11.

If you’d like to try this yourself in the meantime, the following line in main.cpp creates the detector for the 36h11 family: here

To add support for the tagCustom48h12 family, you can:

Add the include:

#include <tagCustom48h12.h>

Replace the detector creation line with:

tf = tagCustom48h12_create();

Please note that this change may affect the current functionality, you’ll likely need to make additional modifications in main.cpp to ensure it builds and runs correctly.
As mentioned, we’re actively working on making this a much smoother process in the future. But if you’d like to get started now, the above steps should point you in the right direction.

]]>https://forum.modalai.com/topic/4830/setting-up-different-apriltag-familieshttps://forum.modalai.com/topic/4830/setting-up-different-apriltag-familiesTue, 21 Oct 2025 14:14:12 GMT<![CDATA[VOXL2 NOT DETECTING APRIL TAG]]>Detections is pertinent to voxl-tflite-server and onboard computer vision on yolo, NOT on april tags.

]]>https://forum.modalai.com/topic/4720/voxl2-not-detecting-april-taghttps://forum.modalai.com/topic/4720/voxl2-not-detecting-april-tagMon, 01 Sep 2025 17:13:46 GMT<![CDATA[Using Relocalization to establish a global reference frame for Drone Swarm Demo]]>@Eric-Katzfey Thank you for the reply,
If I understand correctly, the example you provided shows MAVSDK running directly on the VOXL — so on the drone itself. However, we want to run our script on a separate PC to be able to control all drones at once. We're not sure which port to use to communicate with PX4 while also taking advantage of the relocalization handled by VOXL.

Thank you again for your help!

]]>https://forum.modalai.com/topic/4372/using-relocalization-to-establish-a-global-reference-frame-for-drone-swarm-demohttps://forum.modalai.com/topic/4372/using-relocalization-to-establish-a-global-reference-frame-for-drone-swarm-demoWed, 23 Apr 2025 14:26:53 GMT<![CDATA[Enabling Hires Camera for AprilTag Detection]]>@Madelyne-Rossmann , sounds good! We will work on enabling larger resolutions for calibration and tag detection. It is a bit of a hassle due to very large frames, so some optimizations need to be made.

Alex

]]>https://forum.modalai.com/topic/4153/enabling-hires-camera-for-apriltag-detectionhttps://forum.modalai.com/topic/4153/enabling-hires-camera-for-apriltag-detectionWed, 05 Feb 2025 17:30:41 GMT<![CDATA[Apriltag relocalization not relocalizing?]]>@Nitin-Varma-Vegesna said in Apriltag relocalization not relocalizing?:

@Nitin-Varma-Vegesna Is there any release that is known to work for April Tag Detection?

https://gitlab.com/voxl-public/voxl-sdk/services/voxl-tag-detector

The dev branch is the most recent - I have to check with the engineering team on this as I am unsure the priority of april tag detection and positioning based off it. Will relay back

]]>https://forum.modalai.com/topic/4120/apriltag-relocalization-not-relocalizinghttps://forum.modalai.com/topic/4120/apriltag-relocalization-not-relocalizingFri, 24 Jan 2025 14:18:11 GMT<![CDATA[Apriltag as a reference cordinate]]>Problem solved,
Thanks anyway

]]>https://forum.modalai.com/topic/4118/apriltag-as-a-reference-cordinatehttps://forum.modalai.com/topic/4118/apriltag-as-a-reference-cordinateFri, 24 Jan 2025 13:03:39 GMT<![CDATA[mavlink set_position_target_local_ned does not seem to be transformed]]>Spot on @Matt-Ooi - the voxl2 is natively meant to handle transformations for ardupilot and px4 - BUT you are using MAVROS which is a different tranformation all together - hence why you would have to do the transofmratio yourself before sending into the flight stack running ardupilot (aka when calling mavros offboard) or something

]]>https://forum.modalai.com/topic/3889/mavlink-set_position_target_local_ned-does-not-seem-to-be-transformedhttps://forum.modalai.com/topic/3889/mavlink-set_position_target_local_ned-does-not-seem-to-be-transformedMon, 28 Oct 2024 05:51:28 GMT<![CDATA[Hires With AprilTags]]>@Alex-Kushleyev yes seems like it, thank you!

]]>https://forum.modalai.com/topic/3684/hires-with-apriltagshttps://forum.modalai.com/topic/3684/hires-with-apriltagsSun, 28 Jul 2024 09:58:03 GMT<![CDATA[Using april tags for relocalization during offboard "trajectory" mode]]>@iparra have you read through the documentation on how to configure the tags? https://docs.modalai.com/voxl-tag-detector/#voxl-configure-tag-detector

]]>https://forum.modalai.com/topic/3462/using-april-tags-for-relocalization-during-offboard-trajectory-modehttps://forum.modalai.com/topic/3462/using-april-tags-for-relocalization-during-offboard-trajectory-modeTue, 21 May 2024 16:00:33 GMT<![CDATA[[yocto:/# roslaunch voxl_cam_ros tracking_slave.launch] Error Message ?]]>@Hyosun-Yoo said in [yocto:/# roslaunch voxl_cam_ros tracking_slave.launch] Error Message ?:

Re: AprilTag Relocalization

Dear
I got an error message when I run this command.

[yocto:/# roslaunch voxl_cam_ros tracking_slave.launch]

Please tell me how to solve this message.

VOXL Vision (modalai-3-2-0-0.3.4-b.tar.gz)
VOXL Vision PX4 Apriltag Relocalization error

Error message

ERROR: could not open camera subscriber for cam id 1
[ERROR] [1034.046473200]: CameraManager::Initialize() failed
[ERROR] [1034.046845023]: Unable to open camera.
===============*
5c2c6beb-9c8b-432b-8430-fcc4d81c1ef3-image.png

Thank you so much.
Mr. Yoo, hyosun

]]>https://forum.modalai.com/topic/1212/yocto-roslaunch-voxl_cam_ros-tracking_slave-launch-error-messagehttps://forum.modalai.com/topic/1212/yocto-roslaunch-voxl_cam_ros-tracking_slave-launch-error-messageWed, 17 Aug 2022 00:02:18 GMT<![CDATA[Fiducial precision landing - AprilTags or ArucoTags]]>For information on AprilTag detection, please see our VOXL SDK documentation here

]]>https://forum.modalai.com/topic/775/fiducial-precision-landing-apriltags-or-arucotagshttps://forum.modalai.com/topic/775/fiducial-precision-landing-apriltags-or-arucotagsTue, 01 Mar 2022 18:45:02 GMT<![CDATA[Documentation for AprilTag Relocalization?]]>Documentation updated here!

]]>https://forum.modalai.com/topic/514/documentation-for-apriltag-relocalizationhttps://forum.modalai.com/topic/514/documentation-for-apriltag-relocalizationMon, 25 Oct 2021 15:59:38 GMT