These paper charts are digitalized. 
There are two different methods:

1. Raster charts
In this technique the chart is scanned into the computer and a longitude/latitude grid is laid over it. Because this method is simple to realize, these charts are affordable and perfect to start with. They they look like paper charts, so it is quite easy to work with them.

Chart manufacturers :
- Maptech / chart format BSB or BSB4
- Delius Klasing / own chart format

Software manufacturer:
- Maptech Chart Navigator
- Raymarine Raytech Navigator
- MaxSea
- Fugawi

This method has one disadvantage: You always have to switch between charts and scales.(Fugawi). From track chart to detailed charts and the harbour plan, like known with paper charts.
Some programs automatically change to the chart with the best scale (Maptech). That means, when you reach the coast, they automatically switch to detailed charts. 
Some programs also show the detailed maps inside the track chart, when a certain scale is chosen (MaxSea & Raytech & Maptech).
When you zoom in these charts, information, like numbers, lines and buoys appear bigger.

2. Vector charts
From paper charts the information, like buoys, depth contours, shore lines, nav aids, prohibited areas etc. is copied by hand. The information is then stored together with the position. In the data base appears e.g. "red buoy, 54°N 12°E". When this chart area is shown, the program draws a red buoy in this position. If you zoom in, the buoy is alway shown in the same position and size. This technique also allows to fade information in or out. You can seamlessly scroll from one area to the other. Also you don´t have to change charts, it´s all in one. The production is very compex, that´s why these charts are more expensive than raster charts.

Chart manufacturers:
C-Map
Navionics
Transas

Software manufacturers:
MaxSea
Raymarine Raytech
Transas Tsunamis

2a Vektor charts for Chart Plotters
These vector charts are also used in chart plotters on memory modules (Navionics & C-Map). In course of time different versions were developed, wich often caused confusion.
Here you can find an overview.

C-Map
C-Map CF85 modules (from 1985 on), C-Map NT 95 modules (from 1995 on), C-Map NT+ Module (from 2001on), C-Map MAX (from 2005 on), C-Map CM93 CDs (from 1993 on)

Navionics
Microcharts (credit card size, from 1985 on), Navcharts (from 1994 on), Gold Charts (on CF, MMC & SD cards from 2001 on), Platinum Charts ( from 2006 on), Magellan BlueNav

Transas
Garmin BlueChart

Please read your manual closely, which memory modules are required; you also can ask us.

General information
Paper chart information already are partly incorrect, so digital charts cannot be better. Many charts have been surveyed about 30 to 50 years ago with former methods, they contain incorrect positions. With todays GPS technology you have an accurracy of approx.10 m.With the old surveying techniques, that was not possible. So, e.g.the last chart of New Zealand that was drawn by Captain Cook, was again surveyed and edited just in 2002. 
That means, you can never rely on electronic charts on board of recreational yachts. Often you can find deviations of 100-300m. You are depentent on the lookout, the paper chart and accuracy in navigation.

For sure, electronic charts are improved continuously.The worldwide nautical data bases of the manufacturers are revised in turns every 2 to 4 years. But it also can happen, that some harbours already exist for 3 years and didn´t appear in the charts yet. On the other hand, some changes (e.g. in the notices to mariners) can be inserted faster.

In general, neither in paper- nor in electronic charts remote areas are registered as well as frequently travelled areas.

Recognized mistakes can be reported to the manufacturers, and will be corrected in the following versions. Navionics offers a special correction form.

Development
The costs for these cards considerably dropped in the last couple of years. Faster PCs and larger sized memory cards let the mapped areas grow. So Navionics already offers XL9 charts and C-Map offers Max Mega Wide modules. The coverage with raster charts grows annually.

back