ECDIS is able to determine the status of the chart data being displayed by inspecting the information contained within it. When any part of the screen area displays data that is not generated from ENC then ECDIS should provide an indication similar to the following:
No official data available. Refer to paper chart
The boundary between ENC and other chart data is also clearly identified on the ECDIS display by a special line style. A diagonal stroke will appear on the side of the line containing the non-official data. ECDIS which are still using the first version of the S-52 Presentation Library are likely to show the diagonal stroke incorrectly on the side of the line containing ENC.
Ref: Marine Teacher Website
