Patch size description on the Data Products page

The DP0.1 Data Products page quotes the DESC DC2 paper as saying that “each patch is 4100x4100 pixels”. However, after grabbing some patches with the butler, I see that this description doesn’t straightforwardly correspond to what patches actually look like. A typical patch in the middle of a tract takes up 4200x4200 pixels, a patch on an edge of a tract (and not on a corner) has 4100x4200 (or 4200x4100) pixels, and a corner patch has 4100x4100 pixels. Neighboring patches within a tract overlap by 200 pixels.

All of this is more consistent with the following scheme: Each patch has an “interior” region of 4000x4000 pixels. The interior regions of all the patches tile the tract without overlapping. Each patch is additionally surrounded by a “fringe” of 100 extra pixels on every side (except for patches on the edge or corner of a tract, which lack fringes along the tract edges). The fringes extend into the interior regions of neighboring patches, so that neighboring patches within a tract have a total of 200 pixels of overlap.

Is this correct?

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Yes. What you call a “fringe” is generally referred to in the pipeline as “overlap” or a “border”.

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