[D] 2D-positional encoding for Transformer

I'm working with 2D input, where I have discrete objects arranged in a grid-like structure with one temporal dimension and one spatial dimension. I'd like to process these inputs with a Transformer. Any idea what would be a suitable positional encoding to use for this? I could probably use something similar to what is used in ViT (2 spatial dimensions), but maybe there's something more suitable for the mixed "temporal-spatial" case?

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encoding grid machinelearning objects positional encoding process something temporal transformer