Offshore G-charts come in several sizes and the price of any chart cartridge is based on the amount of memory required to store all the charts in any one particular cartridge. The larger the geographic coverage, the more charts are included, and the larger the memory and price.

Port Services - Maximum detail everywhere within the cartridge, with best general zoom range to 1 nm. Depth contours and some spot soundings are provided. Port plans are included to the best possible range, usually 1/4 nm or 1/8 nm, and includes port service details. An "S" represents this type of cartridge.

Extra Detailed - Maximum detail everywhere within the cartridge, with best general zoom range to 1 nm. Depth contours and some spot soundings are provided. Port plans are included to the best possible range, usually 1/4 nm or 1/8 nm. An "X" represents this type of cartridge.

Detailed - Detail everywhere within the cartridge, with best general zoom range to 2 nm. Depth contours are provided. Best range for the included port plans is usually 1/4 nm or 1/8 nm. A "D" represents this type of cartridge.

Fishing - Best general zoom range is usually 2 nm. Contains extended depth contours, details of underwater canyons, banks, wrecks, bottom obstructions, and fishing information. May have port plans included, with best zoom range to 1/4 nm or 1/8 nm. An "F" identifies this type of cartridge.

General - Best general zoom range is usually 2 nm or 4 nm. Few depth contours are provided. May contain port plans with best zoom range to 1/4 nm or 1/8 nm. A "G" represents this type of cartridge.

Coastal - Best general zoom range is usually 1 nm or 2 nm. May or may not contain depth contours. Does not contain port plans. A "C" identifies this type of cartridge.

Occasionally, boaters notice that their electronic chart doesn't duplicate a particular feature shown on the paper chart they're using. The reason is this: Offshore G-charts and Navionics use all the best charts available and carefully turn the paper charts into a digital format for display on electronic chart plotters. If there are errors, omissions, or discrepancies on paper, they may occur electronically too.

On paper charts, sometimes even large features like a breakwater may not be shown clearly or at all. Large breakwaters are sometimes not shown on the harbor charts, but are shown on coastal charts-or vice versa. These decisions are made by the chart maker, NOAA/NOS.

In some cases, bridges or other features washed away in storms decades ago are still shown on the paper charts. Recent changes in coastlines are often not reflected on paper charts for years. The same is true for new marinas and ports. Sometimes well-known local landmarks may be shown so small on the paper chart that they are indistinguishable from surrounding features to someone not familiar with the area. In these cases, a feature may not be accurately depicted on the electronic chart.

Even when a feature is shown on the paper chart, it can be overlooked or misspelled in the data entry process. Or a small defect in the coastline graphics produces a "filling" effect on one particular screen. These are small problems that can be easily corrected on the next update, and do not affect the quality of the overall electronic chart.

If you notice something missing on your electronic chart, first check the best available scale paper charts of the area to see how the feature is represented on the paper chart. If we have not represented it accurately, or you know additional information about the feature, give us call at your earliest convenience. We will need to know the chart number, chart maker, and latitude/longitude of the feature along with any other information you can provide. On our next update, we will correct the problem.