Below mentioned are the basic differences between Cancelled ENC & Withdrawn ENC.
Cancelled ENC
“Cancellation” is the term used when an ENC producer issues an update to cancel and delete a base ENC. Since an ENC can only be updated by the ENC producer, similarly an ENC can only be cancelled by the ENC producer. There are two ways in which an ECDIS can manage cancelled ENCs:
A) Automatically remove the ENC from the ECDIS when an ENC is identified as cancelled. The user is informed of this during loading of the data or at the end of the process.
B) Allow the user to decide whether to retain the ENC on the ECDIS or remove it. If the user chooses to retain the ENC, a permanent warning will be displayed on the screen whilst the cancelled ENC is viewed. Such ENCs may not be up-to- date and must not be used for navigation.
Also read: What is Block Coefficient and Waterplane Coefficient (Cb and Cw) ?
Withdrawn ENC
“Withdrawal” is the term used when the UKHO decides to withdrawan ENC from AVCS (Admiralty Vector Chart Services), since the UKHO is unable to “cancel‘” an ENC from another ENC producer. The key distinction is that if an ENC is withdrawn, there is nothing to prevent end users continuing to use the ENC until their permit expires.
Note: While ENCs remain withdrawn, they will not be updated and their carriage will not satisfy SOLAS requirements. Mariners are therefore recommended to remove these ENCs from the ECDIS onto which they have been loaded.
ENCS withdrawn from AVCS should be manually removed from the ECDIS and their removal checked periodically. Any ENCs which need to be manually removed from the ECDIS should be recorded in NP 133C.
In essence, both terms indicate that the electronic navigational chart is no longer considered reliable or valid for navigation purposes. Mariners should always use the most up-to-date and accurate charts for safe navigation. The specific procedures and notifications for cancelled or withdrawn ENCs may vary depending on the maritime authority and the chart provider.
