Two derived USGS shoreline maps show the open-Gulf barrier edge recorded at Anclote Key and Three Rooker in 1971 and 2015.
Compare the 1971 FLDEP aerial-derived high-water line with the 2015 USACE lidar-derived mean-high-water line. Both frames use the same USGS coordinate grid and fixed viewport.
Earlier: U.S. Geological Survey, Shoreline date December 1, 1971; source aerials dated December 1971. Later: U.S. Geological Survey, Shoreline date June 15, 2015; source acquisition time and tide are not published here. The control changes only how much of the aligned later frame is visible.
The strongest differences are broad shapes in the mapped outer edge. The later Three Rooker trace is longer, and the southern Anclote Key trace has a different broad form. Read those changes only as two dated USGS shoreline-map conditions, not as complete islands, measurements, or causes.
Visible in the pair: The 1971 open-Gulf shoreline layer contains a short high-water-line trace at Three Rooker, while the 2015 layer contains a longer mean-high-water trace.
Established by the project record: The USGS record identifies the earlier line as a 1971 FLDEP aerial-derived HWL and the later line as a 2015 USACE lidar-derived MHW.
The difference does not establish formation timing, area, distance, rate, cause, or a complete island outline.
Visible in the pair: The 2015 Anclote Key open-Gulf shoreline reaches farther south in the frame and bends differently than the 1971 line.
Established by the project record: The shared USGS coordinate grid and fixed viewport support this broad visual comparison without local shoreline alignment.
The pair does not quantify an offset, define an island boundary, or assign a single cause.
Sources: USGS Florida west coast shoreline data release · USGS 2023 Anclote Key study
Visible in the pair: Both frames display only the USGS open-ocean shoreline segments selected for the two dates.
Established by the project record: The source metadata identifies the layer location as open ocean and preserves different HWL and MHW shoreline proxies.
The absence of a line is not evidence of open water, navigability, access, ownership, a route, or a complete island boundary.
Sources: USGS full source metadata
USGS research describes Anclote Key as a dynamic barrier whose record includes phases of progradation, transgression, and relative stability. A separate USGS Three Rooker image sequence also documents visibly different positions at later dates. Those sources support a cautious reading of the map pair: the records establish two dated conditions, not a rate, prediction, route, or single-cause explanation.
Primary sources: USGS 2023 Anclote Key study · USGS Three Rooker public-domain image sequence · USGS Florida west coast shoreline data release
This story is generated only after both frame records pass the local provenance, rights, checksum, and viewport validator.
Authoritative metadata · Full USGS source metadata · Rights record · USGS shoreline dataset
Authoritative metadata · Source, render, and checksum manifest · Rights record · USGS shoreline dataset
Coastline Memory is historical context. Use the launch guide for access details and the live map for current conditions.
Open the Anclote River Park launch guide · Open the Fred Howard Park launch guide