Quad size is potentially different for each individual mosaic. You’re seeing differences in quad size.
The resolution is the same, but the individual files (quads) have a different number of pixels per file. In other words, some of the mosaics split things up into larger files and others into smaller files. This information is available in the metadata for the mosaic under “grid.quad_size”.
In the case of that specific series, some mosaics have a 2048x2048 pixel quad size and others have a 4096x4096 quad size. The pixel size is the same for both (4.77 * cos(latitude) meters). The difference is only in what size files the overall mosaic is split up into.
Great, thank you! I only saw the 4096x4096 quad size in the documentation so I thought I was doing something wrong. Other than inspecting the metadata, is there some place in the documentation that I could find details like this?
Other than inspecting the metadata, is there some place in the documentation that I could find details like this?
The product specs list 4096x4096, but that’s a generalization and is only meant to be reflective of recent data for select basemap products. The technical specs for all Planet products only give general guidelines for recent data to keep the documents concise, but there can be a large degree of variability outside of the listed guidelines for custom products and older products. For example, almost every detail described in the Basemap technical specifications can be altered for custom deliverables.
In this specific case, data generated in 2016 used smaller workers that did not have enough RAM to produce 4096x4096 quads, so 2048x2048 are used instead. However, only the visual + monthly and visual + quarterly select basemap series are affected. If you were working with weekly visual mosaics or monthly SR from 2016, they would be 4096x4096.
As another example, the Planetscope scene technical specifications are incorrect if you’re looking at 2016-era scenes because they describe current satellites, not past generations. Most satellites in that era did not even have an NIR band, for example, yet the specs will list 4-band data being available all the way back to 2014 to keep the tables in the specification docs simple / more readable.
For all Planet products, it’s important to rely on API metadata rather than assuming data is completely uniform. The specification documents give general guidelines, but the APIs give the specific values for a particular piece of data.
Excellent, thank you for the detailed response!
