By default, all downloads are available in the WGS84 geocentric coordinate system.
If you used custom ground control points, your downloads will also be available in the same coordinate reference system you specified when uploading the ground control points.
If AeroPoints were used, your downloads will also be available in the same coordinate reference system that your AeroPoints survey was processed in. You can find this information by navigating to your AeroPoints survey and inspecting the metadata we include on that page.
If a local grid was used, your downloads will be in the same coordinate system as the local grid associated with your Site.