Updating digital nautical charts is faster and easier

Coast Survey introduces new service for downloading raster chart updates

We click on our smart phone map app, and we can immediately see any place on land. We turn on our boat’s navigational system and a nautical chart appears. Where do the apps get their maps and charts, and how often are they updated? Let’s look deeper into the chart services…

Recreational boaters use chart plotters and computer-based navigation systems, including tablets and mobile devices — at last count, there are over 60 mobile apps — as well as web mapping applications. These commercial products often use privately produced charts derived from official NOAA raster navigational charts (NOAA RNC®). In recent years, larger manufacturers have switched to using NOAA raster charts themselves. Until recently, the systems had to work through a major problem: each of NOAA’s thousand charts is a huge file that takes bandwidth and time to upload. So the entrepreneurs developed work-arounds, especially when they needed to update the charts. Many of them cut NOAA chart files into more manageable “tiles.” Many didn’t update these chart tiles for months, or sometimes even up to a year, despite NOAA issuing updates weekly, often because of time and storage space problems.

chart tile logoCoast Survey listened to the navigation electronics industry, and we collaborated with them to create new chart tile products and services. In December 2015 we announced a prototype of the NOAA Chart Tile Service, which — because of the smaller file size — allowed commercial web mapping applications to quickly access official up-to-date NOAA tiles (sections of nautical charts) while online. The prototype was an immediate success, with the tiles garnering 7.3 million hits in the first three weeks of availability (compared to 1.4 million RNC downloads for the month.) The chart tile service proved so popular that we made it official in April 2016.

Things are now getting even better. On July 15 we introduced an offline tile service, which will enable chart users to quickly download and update only the chart tile sets that have recently changed and use the tiles without having to be online. This will dramatically reduce the bandwidth needed for vessels to keep their chart suite up to date. Maybe more important than reducing bandwidth is having the tile charts available where there is no bandwidth at all. Having the tile charts in your device’s memory means you can use them where you have NO internet connectivity (i.e. no cellular G3 connection).

TECHNICAL SUMMARY

Release 1.0 was released December 7, 2015 with the following features.

Online single chart tilesets

Provides the following capabilities:

  • Generates geo-referenced single chart tilesets from NOAA BSB files. The tileset represents a single NOAA chart at multiple zoom levels.
  • Provides a description of all available tilesets.
  • Demonstrates single chart tileset compatibility with popular mapping APIs.
  • Supplies source code describing tileset integration with each API.
  • Provides a searching capability for kaps/tilesets with a zoom to tileset feature.

This service facilitates production of small- and large-scale development projects and is not intended for navigational purposes.

Online quilted tileset

Provides a unified display of multiple charts. The charts are quilted together to provide a seamless view.

Metadata

Provides WMTS, TMS and TileJSON metadata describing each tileset. In addition, a JSON-formatted UTFGrid metadata file is provided as a companion to each quilted tileset tile.

Release 2.0 released July 15, 2016 with the following additional features.

Offline chart tilesets

Provides single chart and quilted tilesets that are bundled in a single file to facilitate offline use. Offline tilesets are packaged as MBTiles. Additionally, sample mobile app code and developer guides are provided for Android and iOS.

Delta updates

Provides updates to MBTiles that include only the tiles that have changed or been added. Delete tiles are posted as a json file.

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(App developers, see the updated requirements specifications.)

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