# ARUCo : Detecting small markers in a large image

**URL:** <https://forum.opencv.org/t/aruco-detecting-small-markers-in-a-large-image/16063>\
**Category:** C++\
**Tags:** aruco\
**Created:** [January 5, 2024, 12:34pm UTC](https://forum.opencv.org/t/aruco-detecting-small-markers-in-a-large-image/16063 "2024-01-05T12:34:14Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Moddingear](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/moddingear/32/4462_2.png) [@Moddingear](https://forum.opencv.org/u/Moddingear)\
**Post date:** [January 5, 2024, 12:34pm UTC](https://forum.opencv.org/t/aruco-detecting-small-markers-in-a-large-image/16063/1 "2024-01-05T12:34:14Z")

</div>

Hello, I’m using a 4K camera and would like to detect fairly small ARUCo tags on the image. But it seems there is a hard threshold relative to the size of the image. I’ve tried modifying the parameters, such as the minimum rates, but the smaller tags are still not detected.  
I’m wondering which parameter I should change to get these tags to be detected.  
See the example image : I can’t detect the smaller Aruco tags at the back.  
[https://drive.google.com/file/d/1lmmFSdjqre0GiM\_OFAcWctqBs7XyAbiq/view?usp=drive\_link](https://drive.google.com/file/d/1lmmFSdjqre0GiM_OFAcWctqBs7XyAbiq/view?usp=drive_link)

 ![example](https://us1.discourse-cdn.com/flex020/uploads/opencv/original/2X/9/93ed51800a0061dc8efab12e68eb1e8c72206a4d.jpeg)  
Best regards.

PS : I’m using OpenCV 4.8.0, compiled from source, and I adjusted my adaptive theshold constant to 20 as it helps with detecting the bigger tags more reliably.

---

<div class="post-metadata">

**Author:** ![Moddingear](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/moddingear/32/4462_2.png) [@Moddingear](https://forum.opencv.org/u/Moddingear)\
**Post date:** [January 5, 2024, 1:00pm UTC](https://forum.opencv.org/t/aruco-detecting-small-markers-in-a-large-image/16063/2 "2024-01-05T13:00:12Z")

</div>

Turns out that disabling Aruco3 detection helps, it’s worse at detecting smaller tags.  
Also, the threshold minimum size of Aruco3 is minSideLengthCanonicalImg.

What i’ve done is that I have disabled Aruco3 Detection, and multiplied minMarkerPerimeterRate, minCornerDistanceRate and minMarkerDistanceRate by a common factor (in my case, 1/20). This makes the detection of the smaller tags reliable.