A ground-based camera resolution chart, with spaced white bars of known dimensions, for calibrating flying cameras.
https://diqn32j8nouaz.cloudfront.net...alibration.jpg
Previously:
https://www.homemadetools.net/forum/...078#post125674
https://www.homemadetools.net/forum/...990#post125175
https://www.homemadetools.net/forum/...507#post122810
