I've been provided with a large dataset of global-scale polygon maps that I need to integrate into my organisation's existing dataset. Many of the polygons have some edges that are supposed to coincide with coastlines. However, my organisation uses a standard baselayer (gadm28) for coastlines, and the dataset supplied does not - it either matches slightly different coastline edges, or some polygons appear to have been manually drawn to roughly follow coastlines.
Is there any way I can automate the process of editing the new dataset so that the polygon edges match the coastlines of our standard baselayer?
The only method I've tried so far is to manually extend polygons outside the coastlines, then clip using our baselayer, but this is extremely time-consuming and tedious.
Additional information - ideally I need the mapped areas to include islands along coastlines, e.g. along the Norwegian coast (example 1 below). There are instances where small islands have been mapped, but they don't actually coincide with the locations of those islands in our basemap (see example 3). Some polygons also have holes in them, within terrestial regions, that are supposed to be there (see example 2), so I don't want to remove these!
I'm using ArcMap 10.5.1. I'm not familiar with Python (although I can try).