Frequently Asked Questions about NOAA 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 do data from NOAA ENC Direct to GIS differ from data found in NOAA ENCs?
4. Where do all of the data layers in NOAA ENC Direct to GIS originate?
5. Why aren't all NOAA ENCs available through NOAA ENC Direct to GIS?
6. Where can I find information about the NOAA ENC Direct to GIS layers?
7. How are the data layers in NOAA ENC Direct to GIS organized?
8. Why are some of the S-57 object classes separated into individual geometry layers (point, line, polygon)?
9. Why can I only see certain layers when I am zoomed into a particular scale?
10. What is the update frequency of NOAA ENC Direct to GIS and how accurate is the data?
11. How do I download data from NOAA ENC Direct to GIS?
12. How long will it take to download my data?
13. Can I download data if I have a pop-up blocker?
Answers to Frequently Asked Questions
Question 1 - What Web browsers work best with NOAA ENC Direct to GIS?
Answer - Recommended browsers are Netscape 7.x and Internet Explorer 6.x. (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 ENCs for navigation at http://nauticalcharts.noaa.gov/mcd/enc/index.htm. (Back to top)
Question 3 - How do data from NOAA ENC Direct to GIS differ from data found in NOAA ENCs?
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 from merging S-57 object classes from all large scale NOAA ENCs into seamless layers. For example, the coastline layer is a composite of the S-57 object class COALNE from all current Approach and Harbor ENCs. (Back to top)
Question 5 - Why aren't all NOAA ENCs available through NOAA ENC Direct to GIS?
Answer - NOAA ENCs have been compiled at different scale bands. Merging ENCs of varying scale cause data overlap in the layers. Only large scale ENC data are available at this time. (Back to top)
Question 6 - 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. (Back to top)
Question 7 - 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 8 - 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. NOAA ENC Direct to GIS is built using ESRI's ArcIMS software, which does not support multiple geometry types in individual layers. 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 9 - Why can I only see certain layers when I am zoomed into a particular scale?
Answer - NOAA ENC Direct to GIS layers have scale dependency. This means that they are only visible when zoomed into at least a minimum scale. This speeds up the map service and reduces data clutter in the map frame. Generally, as you zoom in, more data becomes visible. (Back to top)
Question 10 - 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)
These new versions of NOAA ENC cells are added to the NOAA ENC Direct to GIS site on the first workday of every month. This means that the data on the NOAA ENC Direct to GIS site will not include the changes that are produced as update patches. This is one of the main reasons why NOAA ENC Direct to GIS data are not for navigational use.
Any new NOAA ENC cells that are added to the NOAA ENC portfolio are also added to the NOAA ENC Direct to GIS site on the first workday of every month.
Data contained in the NOAA ENC Direct to GIS site retains the accuracy of the original NOAA ENC data. (Back to top)
Question 11 - How do I download NOAA ENC Direct to GIS?
Answer - Click the “Extract” button from the toolbar menu to bring up the Data Order Form. For detailed instructions on how to use the Data Order Form click here (Data order form Link) (Back to top)
Question 12 - 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 much quicker than downloading layers for a large spatial extent. It is recommended when choosing to download layers using a large spatial extent to only download single layers at a time. Certain layers cannot be downloaded in their full spatial extent due to output format size limitations. It is difficult to calculate this. If you receive a translation failure, please select a smaller spatial extent. (Back to top)
Question 13 - Can I download data if I have a pop-up blocker?
Answer - No, in order to download data you must have your browser’s pop-up blocker turned off. (Back to top) |
