Listed April Tag locations don't match coordinates given by dimensions in Field Diagram

FIRST General Forum
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#1

Please use this doc for reference while I discuss images in this post.

I’m using the 2023 layout marking diagram found at Playing Field | FIRST to build my own diagram of the field in Desmos; however, when I try to use the dimensions there to determine the coordinates of the apriltags, the y-coordinate does not match with the values in the table in the first image of the doc (this table came in the same document from FIRST).

The second image on that doc shows that knowing the location of the top horizontal red line along with the given distances is all that is needed to determine the y coordinate of each apriltag.

I determined the location of that horizontal line relative to the height of the field using the dimension in the third image of the doc.

The chain of dimensions in the fourth image on the doc also allowed me to determine the height of the field with half the height being (25.61+48 * 2+36.19).

Thus, the field dimensions predict the location of the first apriltag (see last image in the doc) to be 2(25.61+48 * 2+36.19) - 50.50 = 265.1.

The listed height is 265.74 and this 0.64 error persists in the 3 apriltags below it since they are simply defined as 66 inches away from the circled apriltag in the last picture of the doc. The table of “true” apriltag values also lists values 0.64 away from what the field diagram would predict for these other three apriltags.

I was wondering if anyone else had noticed this and knew of an explanation.

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#2

Waiting for the Q&A response noting the +/-1" field tolerance

#3

I believe this issue was found by the wpilib team when creating their json for the field and then corrected for. I’d look for that PR on github.

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#4

Looking at the json at allwpilib/2023-chargedup.json at main · wpilibsuite/allwpilib · GitHub I see the same true values I got from the field diagram chart. I don’t see a pull request related to updating this json file though. However, using the values there I’m able to confirm that my overall field dimensions are not the source of the error.

This 50.50 inch dimension looks like the problematic one in the field diagram:

image
image712×284 22.6 KB

Hopefully, someone can confirm that this dimension is indeed the problem.

#5

Team Update 1 fixes this.

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#6

This is a different thing then what was addressed in TU1

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#7

The field marking diagram shows where the field crew needs to place the red tape. Is there anything that says that the red tape must be perfectly aligned to the AprilTag? I would trust the AprilTag coordinates as provided in the (TU1 updated) table for the AprilTag.

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