DNC Data

Glimpse's DncPainter shows information from Digital Nautical Charts. DNC data for some parts of the world is available for download from the National Geospatial-Intelligence Agency. See [DNC NGA Data Download](DNC NGA Data Download) for detailed instructions on downloading data. (NOTE: For many parts of the world, only patches are available for download, rather than the full database. For rendering purposes, the full database is required.)

The DNC charts come in a form that isn't well suited to fast rendering. Glimpse addresses this problem in two steps:

1. Convert from the original VPF format to DNC_FLAT format, which allows fast loading
2. Project from DNC_FLAT format to DNC_RENDER format, which allows fast rendering

Glimpse writes the DNC_FLAT and DNC_RENDER data to disk. The data can be pretty large (tens of GB), so it is worth thinking through where it should be stored, and possibly overriding the default locations (e.g. by setting the appropriate environment variables). Details about DNC data locations are [here](DNC Data Directories), and more info about Glimpse data locations in general is [here](Data Directories).

Conversion to DNC_RENDER is done on the fly while the painter runs, but conversion to DNC_FLAT has to be done up front.

Converting from VPF to DNC_FLAT

To convert from VPF to DNC_FLAT, run the Vpf2FlatConverter tool in the glimpse-extras-examples module. You only need to do this once for a given set of DNC databases.

In the VPF Parent field, enter the path of the parent directory that contains the DNC database directories:

/home/mike/DNC/
    DNC01/
       A0112483/
       A0112485/
       ...
    DNC02/
    ...

In this case, the parent dir is /home/mike/DNC:

Select the checkboxes for the DNC databases you wish to convert. There are Select All and Select None buttons on the right. Here, we will convert DNC01 and DNC02:

In the FLAT Parent field, enter the path of the destination directory. Typically the default value should be used -- that's where DncPainter will look for the data, by default. Here, we will use the default location for Linux:

Click the Convert button, and wait for conversion to complete:

Running DncPainterExample

If you wrote the DNC_FLAT data to the default location, just run DncPainterExample:

To use a different DNC_FLAT location, run DncPainterExample with the the JVM property -Dglimpse.dnc.flatDir="...".