From OpenStreetMap Wiki
|coastline:survey_quality = complete|
|Denotes a coastline traced from a high quality source|
|Used on these elements|
|Tools for this tag|
This tag is meant to show a coastline where survey data is of a good quality, high resolution, or from an extremely reliable source.
This tag allows renderers to differ between survey quality in accordance with INT 1 symbols C1 and C2.