Marine Data Literacy 2.0

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Home > 2. Marine GIS > 2.29 Nav Charts

2.29 Adding Navigation Charts to Maps in Saga: KAP, BSB, S-57

  • Exercise Title:  Adding Navigation Charts to Maps in Saga: KAP, BSB, S-57

  • Abstract:  After a survey of "free" international sources of navigation charts (which yields only a few States that do so), the exercise goes on to show how to add vector format charts (an enhanced type of shapefile assembly) and raster format charts (a special format developed commercially but now used universally) to maps in Saga.  Individual scientists will probably need to purchase local navigation charts, for most locations, due to the small number of States that provide them freely.

  • Preliminary Reading (in OceanTeacher, unless otherwise indicated):

  • Required Software:

  • Other Resources: 

    • Electronic Navigation Charts (ENCs) - Vector files of navigation charts; composed of shapefiles and annotations

    • Raster Navigation Charts (RNCs) - Raster scans of navigation charts

    • Google List of Online Free Nautical Charts - Some free charts, but mainly for sale by agents.  See the MDL Survey below for more information.

    • 11485.zip (raster RNC) - Chart for area along the east coast of Florida, USA (see source info below)
    • US5FL83M.zip (vector ENC) - Chart for area along the east coast of Florida, USA (see source info below)
    • Nautical Chart Reprojector - Utility program provided by NOAA for reprojecting BSB/KAPS files to orthogonal WGS84
    • World Borders Dataset, by Bjorn Sandvik (use TM_WORLD_BORDERS-0.3.zip)

  • Author:  Murray Brown and Pablo Guilherme

  • Version:   1-10-2014

WARNING:  This exercise is provided only for instruction in how to work with these digital files, and it is not to be a considered as training, instruction or advice in navigation.  Do not rely on the materials here for any maritime purpose, other than study, because they are assuredly out of date and are selected only as examples, and not for any actual use.
  • 1.  The survey of "free" digital nautical chart sites is presented below in the last panel.  You can immediately see that the great majority of States do not provide anything free at all.  Most of them refer you to commercial vendors.  The author has double-checked the Google list and provided further information for States that do provide something.  We salute the following entities for their generous attitude toward earth data: 
    • ARGENTINA
    • BRAZIL
    • MONTENEGRO
    • NEW ZEALAND
    • UNITED STATES OF AMERICA
    • EAST ASIA HYDROGRAPHIC COMMISSION.
2.  Download and install the Nautical Chart Reprojector program.
3.  Run Saga and load the WORLD BORDERS to use for general orientation.
4.  Download the example chart files to the folder DATA > OCEAN > BASEMAP > CHARTS and unzip them in place.  Examine the results and you find these new folders:
  • BSB_ROOT - Contains the raster image files
  • ENC_ROOT - Contains the vector shape files
3.  Here's the contents of the BSB folder.
  • *.BSB - Text file containing the "recipe" for the combined KAP files that follow
  • *.KAP - Individual charts
  • *.TXT - Publisher's notification to users about rights and limitations
4.  The KAP files must be reprojected first. so run the NOAA CHART REPROJECTOR.

NOTE:  This is a very effective program, but the user interface is extremely awkward.  Just be patient and work slowly.

5.  Click on INPUT FILE > BROWSE and this interface opens.  Work very slowly through the DIRECTORIES on the left to find the 11485 folder where the KAP files are located.  Select the first one, and click OK.

NOTE:  If you have trouble finding the right location, just look at the above sequence of folders:

USERS > [NAME] > DOCUMENTS > PROJECTS

Try to follow this same sequence.  Just take your time, and it WILL work.  There are some dead-end routes that will cause trouble, but just keep trying.

6.  Now click on OUTPUT FILE > BROWSE.
7.  Navigate to the same folder as for input, and insert an appropriate filename, with the extension TIF.  Then click OK.
8.  Now you're back to the main panel:
  • Check the INPUT FILE to see that it's got the right name and location
  • Check the OUTPUT FILE to see that it's got the right name and location
  • Set UNITS = DEGREES OF ARC
  • Set FILE FORMAT = TIFF
  • Set PROJECTION = GEOGRAPHIC
  • Set DATUM = WGS_84

Then click RUN

9.  When the program is finished, check the OUTPUT location to see that you have new *.TIF and *.TFW files there.
10.  Select SAGA > TOOLS > IMPORT/EXPORT-GDAL/OGR > GDAL: IMPORT RASTER
  • FILES = New TIF file you just made
  • INTERPOLATION = Nearest Neighbor

Then click OK.

11.  Look for the new raster in the grids section of the DATA panel.
12.  Use ADD TO MAP to place the new raster on the WORLD BORDERS map.
13.  Here you can see the small dark area of the new grid, along the east coast of Florida (or wherever your selection is).
14.  Enlarge it a bit.
15.  And here it has been greatly zoomed to see how it fits.  You can immediately see that the WORLD BORDERS coastline is very crude and does not match up very well.  This is expected.
16.  On your own, you can play with the color scheme.  The raster is a classified grid, with few colors (probably <20).

NOTE:  One author (Guilherme) has experimented with the Saga module VECTORIZING GRID CLASSES to "extract" separate classified zones to polygon shapes from these rasters.  For example, you could create an entirely separate polygon shape for the light brown areas here (probably wetlands).  The possibilities are endless.

17.  Look back to Panel 5, and you'll see that there were 5 other KAP files to work with.  Here they've been mapped separately (using the same steps as above).  You can see that they are subset maps or ancillary maps.  The BSB file is probably the "recipe" for how these maps combine when you have a real electronic chart display system. 
18.  Take the time to save the grids (at least the first one) in Saga grid format, with appropriate names like chart_raster_eflorida_11485_kap1_saga.sgrd
19.  That completes this very short introduction to raster chart usage.  Now we'll look at the vector data.
20.  Here's the contents of the ENC folder.
  • US5FL83M - Folder containing shapes and text notifications for the map
  • CATALOG.031 - Text formulary specifying how the shapes and texts fit together to make a map
  • README.TXT - Information about the map's reliability
  • USERAGREEMENT.TXT - Self explanatory
21.  Look in the US5FL83M folder to find these files:
  • US5FL83M.000 - Primary vector file, in S-57 format, with most of the map objects; contains shapes
  • US5FL83M.nnn - Ancillary shapes; also S-57 format; most are empty here
  • USnnnnnn.TXT - First (of many, not shown) text note to place on the chart

Remember that the file CATALOG.031 specifies how the pieces fit together.  If you have a real electronic chart display system, everything will be integrated accordingly.  With Saga we can only use the pieces separately, and admire the technology involved.

22.  Select SAGA > TOOLS > IMPORT/EXPORT-GDAL/OGR > OGR: IMPORT VECTOR DATA
  • FILES = First (and primary) S-57 file

Then click OK.

23.  These LINE, POINT and POLYGON shapes appear in Saga.
24.  Here is the line shape.  It's also the east coast of Florida.
25.  Here is a zoomed section of the northern end.  The WORLD BORDERS shape is included just to orient you.  They don't match because WORLD BORDERS is very crude, compared to the ultra-fine precision of a good navigation chart.
26.  Here we've selected the line shape and selected ATTRIBUTES > SHOW to see the DBF table for it.  Clearly you'll have to do a lot of research to find out the meaning of the fields.  None of them is a clean list of feature names, so labeling won't be easy.
27.  But you can use the fields (after your own research) to work with the coloring.  The yellow polygon is from the World Borders, providing a classic example of how badly low-resolution data would serve us for coastal zone purposes.
28.  Here is the point shape, with one of the fields used for labeling. 

Much work would be needed to convert these codes to understandable labels.

29.  And here is the polygon shape, colored by one of the fields.  These are roughly similar to what you'd get if you vectorized the grid classes from the KAP maps, as mentioned in Panel 16.

NOTE:  The broad band of blue represents the legal "territorial sea" of the USA.  This is a very old concept, predating Law of the Sea zones which go much farther out.

30.  Just having the files and knowing, now, how to get them into GIS, is only half the problem.  It's up to you to do the research to find out what these codes in the ATTRIBUTES table mean.  Remember, you don't have an electronic chart display system, so you're peeking into a different world and trying to capture useful information for other purposes, so expect a lot of work.
31.  Take the time to save the new shapes to the folder PRODUCTS > SAGA > VECTORS > CHARTS with name like these.
32.  The above methods cover only the mechanics of getting these valuable (but often neglected) map objects into your GIS.  The research needed to understand the different features is all up to you.  You can't use a map like the one in Panel 28, because nobody knows what a #39 means, so get ready for some extra work.
33.  MDL Survey of Free Digital Navigation Chart Availabilities

Based on the Google List cited above.  Presumably all countries' charts can be found either at the websites listed in the Google List or through the IC-ENC website.  The MDL survey below is intended to highlight truly "free" digital charts, such as they are.  Due to the many URLs at each country, you must go through the Google List to research the contents on the MDL survey.  The few links below are to special pages within the cluster of citations for each country in the Google List.  Countries with no information do not provide free digital charts of any kind, don't provide clear guidance on what's really available or how to get it, don't have enough English language information to make any determination, or only provide chart visualizations of unknown projections (i.e. not WGS84).  Several States do provide dynamic websites where you can view (but not download) maps; these online maps are not described here.

Country Availability Typical Download Notes on Resources
Argentina Free downloads H118.ZIP RAR files mislabeled as ZIP.  Change extension to RAR, then unzip with 7zip or WinZip.  Contents are BSB + KAP rasters; can be read with Saga's GDAL grid input module
Australia, Belgium - Nothing free found; please notify the author if wrong.
Brazil Free downloads 1822.ZIP ZIP files containing BSB + KAP rasters; can be read with Saga's GDAL grid input module
Canada, Chile, China, Columbia, Croatia, Denmark, Ecuador, Egypt, Estonia, Finland, France, Germany, Iceland, India, Italy, Japan, Rep. Korea, Latvia, Lithuania, Mexico - Nothing free found; please notify the author if wrong.
Montenegro All available WGS84 charts (2) available as PDF 05-01.pdf The reference to WGS84 is the very civilized way the Montenegrins inform us that the maps are not projected and can be georeferenced, i.e. in Saga.  They are applauded for this information.  Use the method in 2.14 Image Georeferencing in Saga.
Netherlands - Nothing free found; please notify the author if wrong.
New Zealand Annual compilation of all raster digital charts available free (180 MB); also the free sample here A sample raster file New Zealand BSB Test Dataset; All rasters are BSB/KAP format, so can be loaded into Saga with the GDAL import module
Norway, Panama, Peru, Poland, Portugal, Russia, Singapore, Slovenia, Spain, Sweden, Turkey, United Kingdom - Nothing free found; please notify the author if wrong.
USA Online catalog interfaces to all vector (S-57 format) and raster (BSB/KAP formats) charts
  • ENC charts unzip to yield S-57 format file, which can be read with Saga's OGR vector input module (to yield point shapes, line shapes and polygons), plus TXT notes to annotate the charts.   Main file to load has extension 000
  • RNC charts unzip to yield BSB/KAP format, so can be loaded into Saga with the GDAL import module.
Uruguay, Venezuela - Nothing free found; please notify the author if wrong.
East Asia Hydrographic Commission   South China Sea charts (vector ENC) To download the SCS ENC, user has to register with the EAHC.  Not checked by MDL.