One high-res pass a year, the waterline taken off it by the same rule each time, and a retreat or accretion rate for each shoreline segment you define.
The first delivery covers the first pass. Each year after that adds a new waterline and updates the rates.
The coastal stretch as a line or polygon, and your shoreline segments, as a GeoPackage or shapefile. If you already hold a baseline and transects, send them too.
High-res multispectral imagery for the stretch, once a year.
The same optical rule is applied to every year's image, and change is measured between years along each segment.
The waterline layer, the segment rate table, the segment layer and the method note, in formats that open in QGIS or ArcGIS.
The new pass is added to the same record and the rates are updated.
The shoreline behind your setback line review was probably digitised from old aerial photographs, then joined to beach profiles walked at a few sites. Different methods, different years, so a rate across the whole frontage mixes surveys never made to be compared. A repeat ground survey of the full stretch means a contractor, a tender and a season of waiting, and the plan review date stays where it is.
No. It is a repeatable waterline extraction from imagery. A survey gives you vertical detail and datum-referenced positions that imagery cannot.
By one optical rule applied the same way every year. It is the edge in the image at capture, with no correction to a tidal datum.
0.5–2 m GSD. Change of a pixel or two between passes will not show, and a low-contrast shore may extract less well.
Once a year. Storms and seasons are outside it.
Yes, both. Cloud can push the pass later, and the tide at capture moves where the line falls. The method note records them for each year.
The waterline layer carries a date on every line and the rates arrive as a CSV. If you run your own baseline and transects, send them and the change can be measured along them.
Every line carries its image date, so you can lay it over a ground survey or profile from the same period and see the gap. Tell us where your ground data sits when the stretch is scoped.
Use and ownership terms are set in the contract before work starts. The imagery behind the lines keeps its own licence.
Each stretch is scoped and quoted on its own: length of coast, number of segments and how many years you want going forward. You get a written scope for procurement.
Or ask about your coastline in the .