Furuno FCR-2107 series, Руководство оператора

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7. Vector Chart Material
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7.5 S57 Chart Service from an RENC
7.5.1 Introduction
Before you can use an RENC service, you have to be authorized as a customer of an RENC. To be authorized you
have to contact an official distributor (chart agent) of RENC. Then, the following services are available:
7.5.2 Permits
Permits are used to control the permission to use a chart. A permit in RENC security is connected to an edition.
Permits are issued as two different types:
•
Subscription permit. These include updates for subsequent 12 months. It is assumed that a typical user is a
SOLAS class ship, which is required to use up-to-date charts.
•
One-Off permit. These include only updates up to the issue date of the permit. It is assumed that a typical
user is a non-SOLAS class ship, which is not required to use up-to-date charts.
Each permit also includes the expiry date. The expiry date of a permit controls the ENC to SENC conversion. If the
issue date of a chart or update is older or equal to the permit expiry date, then the system can convert an ENC into
the SENC. There are no viewing time limits as used in some other security systems. The user has a right to view a
chart forever and moreover he has a right to convert a chart from its ENC format into the SENC forever.
An RENC can issue permits in two formats:
•
"*.pmt" format. This format does not include the applicable chart edition nor does it include applicable
permit type.
•
PERMIT.TXT format. This format includes the applicable chart edition as well as applicable permit type.
Both permit formats are fully operational, but the older "*.pmt" format creates confusion because it cannot support
the user when chart edition changes.
The system display warnings associated with expiry date. Examples are "will expire" warning 30 days before the
expiry date and "have expired" after the expiry date. These warnings are relevant only for Subscription permits.
Only the new PERMIT.TXT format supports the system to suppress irrelevant warnings associated with expiry date.
7.5.3 Product list
A Product List is maintained by an RENC. You can retrieve the Product List from an RENC via telecommunications
or you can load it from the CD ROM of an RENC. This list contains an up-to-date list of available charts and their
edition/update status in an RENC. When you load a CD ROM or use telecommunications to receive a Product List
from an RENC, the chart radar checks the issue date of the Product List. If the issue date indicates a newer Product
List, then it is copied into the chart radar. If the issue date indicates an older Product List, then chart radar shows a
notice to the user that newer Product List is already loaded.
7.5.4 Authentication
Normally the authentication process is invisible to the user. Only if the authentication fails, then the user gets an
appropriate notice. From a user point of view, the authentication is similar to the CRC checksum test. If the CRC
checksum test or authentication fails, then the chart is unusable.
Authentication uses a private key and a public key. A digital signature associated with each chart contains a private
key. A public key is stored in the chart radar and it is truly public. RENC may publish a new public key. This public
key will be available as text by fax, by post, by front page of a newspaper, etc. and as a text file, for example,
PRIMAR.PUB.