Frequently Asked Questions about NOAA ENC® Direct to GIS

Don't forget to visit our How-To for answers to specific questions about using NOAA's ENC® Direct to GIS.

Click on a question listed below to jump to the answer on this page.

1. What Web browsers work best with NOAA ENC® Direct to GIS?
2. Can I use NOAA ENC Direct to GIS for navigation?
3. How does data from NOAA ENC® Direct to GIS differ from data found in their respective NOAA ENC®?
4. Where do all of the data layers in NOAA ENC® Direct to GIS originate?
5. Where can I find information about the NOAA ENC® Direct to GIS layers?
6. How are the data layers in NOAA ENC® Direct to GIS organized?
7. Why are some of the S-57 object classes separated into individual geometry layers (point, line, polygon)?
8. Why can I only see certain layers when I am zoomed into a particular scale?
9. What is the update frequency of NOAA ENC® Direct to GIS and how accurate is the data?
10. How do I download ENC data from the NOAA ENC® Direct to GIS application?
11. How long will it take to download my data?

Answers to Frequently Asked Questions

Question 1 - What Web browsers work best with NOAA ENC® Direct to GIS?

Answer - The recommended browsers are the latest versions of Internet Explorer, Firefox, Safari, and Chrome.  (Back to top)

Question 2 - Can I use NOAA ENC® Direct to GIS for navigation?

Answer - No, NOAA ENC® Direct to GIS is not certified for navigation. You can download NOAA ENC® files for navigation at http://nauticalcharts.noaa.gov/mcd/enc/index.htm.   (Back to top)

Question 3 - How does data from NOAA ENC® Direct to GIS differ from data found in their respective NOAA ENC®?

Answer - NOAA ENC® Direct to GIS data is in a format that is not certified for navigation. The data is derived from the official NOAA ENCs through GIS conversion software.  (Back to top)

Question 4 - Where do all of the data layers in NOAA ENC® Direct to GIS originate?

Answer - The data layers have been created by merging S-57 object classes from all NOAA ENCs into seamless layers. For example, the coastline layer for Approach and Harbor scale band is a composite of the S-57 object class COALNE from all current Approach and Harbor ENCs.  (Back to top)

Question 5 - Where can I find information about the NOAA ENC® Direct to GIS layers?

Answer - The S-57 object catalog can be used to look up NOAA ENC® Direct to GIS layer and attribute definitions. A free, on-line S-57 Object Catalog is available at http://www.s-57.com. This service is for informational purposes only and does not constitute an endorsement by the U.S. Government. In addition, you may click the 'Description' from the 'ENC Scale Band' drop down list for each scale band to get a list of available GIS layers. (Back to top)

Question 6 - How are the data layers in NOAA ENC® Direct to GIS organized?

Answer - The data layers have been grouped in folders by thematic categories that describe the layers that they contain. NOAA ENC Direct to GIS contains over 200 data layers. Layers can be found by navigating through the appropriate folders/subfolders.  (Back to top)

Question 7 - Why are some of the S-57 object classes separated into individual geometry layers (point, line, polygon)?

Answer - S-57 object classes contain multiple geometry types. For example, the WRECKS object class can contain point and polygon features. It is important to note that an S-57 object in NOAA ENC Direct to GIS can have point, line, and polygon parts.  (Back to top)

Question 8 - Why can I only see certain layers when I am zoomed into a particular scale?

Answer - NOAA ENC® Direct to GIS layers are configured with scale dependency.  The data will be displayed by scale band.  As you zoom in at certain scale ratio, the application will display ENC data compiled for that scale band.  For example, if you zoom in at scale 1:36,112, the application will display ENC data within the Approach and Harbor scale band.  If you would like to find out which scale band you are viewing, simply click on the screen and a popup window will appear displaying the current ENC name.  

Question 9 - What is the update frequency of NOAA ENC® Direct to GIS and how accurate is the data?

Answer - The NOAA ENC® cells that are intended for navigational use are updated for Notices to Mariners and other information that affects the safety of navigation. These updates are provided to navigational users of NOAA ENC cells as update patches. Periodically, NOAA ENC® cells are released as complete new versions (called New Editions when referring to paper charts) that include all of the update patches.  (Back to top)

The data used for the NOAA ENC® Direct to GIS site will be updated on Saturday night every week. This includes all of the update patches or new editions available at the moment the data is being refreshed.

Data contained in the NOAA ENC® Direct to GIS site retains the accuracy of the original NOAA ENC® data.  (Back to top)

Question 10 - How do I download ENC data from the NOAA ENC® Direct to GIS application?

Answer - Follow the instructions below to download ENC data from the NOAA ENC® Direct to GIS application:

• Click the “Data Extract” button from the top toolbar and choose one of the scale bands from which to download data. For example, selecting ‘Extract Overview’ allows you to download data within the Overview scale band.
• Select the desired draw tool in 'Select area' and draw the shape on the screen to identify the chosen geographic area.
• Check the box(es) next to the layer name(s) to select layer(s) to download.
• Select the file format for the output.
• Click ‘Extract.’
• You will be prompted to save a .zip file locally. Please note: Each data extract will be saved with the same .zip filename. Be sure to rename your downloaded file before the next download in order not to overwrite your previous data.

Question 11 - How long will it take to download my data?

Answer - The time varies and depends on your Internet connection and the amount of data you wish to download. Downloading layers that have a smaller spatial extent is generally quicker than downloading layers for a large spatial extent.  (Back to top)