[Openev-discuss] OpenEV and S-57 data

[David H. <dhe...@mo...>]

I'm interesting in finding, or perhaps building, a small open source
viewer for NOAA ENC (S-57) files. I've tried SeeMyDENC from SevenCs,
it's free, works very well, but doesn't appear to be open source. OpenEV
will load S-57 files and display them, but unless I'm missing something
(very possible) OpenEV requires some modification to load, display, and
allow the end user to play with S-57 data in usable manner.

Since OpenEV is a reference implementation, not a targeted application,
what follows may not be relevant to OpenEV developers or users. But I
thought it might be worth posting my questions in this forum. Note I'm
using Linux (RH FC3) and openev-linux-180.tar.gz

A general question:

Have others worked on S-57 viewers, or modified OpenEV to display S-57
data? If so, can you point me to any other useful documentation, other
source code, or offer any advice. My fear is that I'm reinventing the
wheel. If not, it's possible I'm writing code, or coming up with
documentation that might help others.

Some specific questions (note details below):

1) Setting S57_CSV in the environment helps, but is not documented. Are
there other environment variables that might help?

2) Can longer more descriptive S-57 object names be displayed on the
OpenEV user interface?

3) Is there a way to see 'reasonable' S-57 object colors at load time?

4) Why is text text data, place names e.g., missing on the OpenEV
display?


Details:

1) I notice OpenEV, actually GDAL/OGR, will parse out S-57 short object
names, not just primitives, if the environment variable S57_CSV is set
and points to a directory containing s57objectclasses.csv, and
s57attributes.csv, two files included in the GDAL source tree. This is
not documented in OpenEV. Are there other environment variables or
external files that may help S-57 data display? And, is it possible
S57_CSV should be documented in OpenEV help?

2) In places like the layers dialog, users probably want to see
descriptive S-57 object names rather than short names ('Cargo
transshipment area' not 'CTSARE' e.g.).  OpenEV is easily modified to
accommodate this. I modified a few files to look for S57_CSV in the
environment, find s57objectclasses.csv, parse it, and create a
dictionary mapping short names to long. The dictionary is used to render
things like the layers dialog where object names are displayed to the
user. Is there a way to do this without modifying source? If not is my
small modification useful to others?

3) There should be a way to map S-57 objects to colors. Have others have
already done this? By default every S-57 object OpenEV displays is
green. My next OpenEV tweak will be to map S-57 objects to colors using
paper charts and printed documentation as a guide.  The object to color
mapping would be persisted similar to the existing S57_CSV files and
used to display S-57 objects in 'reasonable' colors with OpenEV at load
time.

4) I notice text data is included in the S-57 data I load, but not
displayed in OpenEV, is this expected behavior? If I load an s-57 data
file in a text editor I see place names, but they don't appear on the
display with any object.



My thanks in advance for any help,


David
dhe...@mo...