[gdal-dev] sounding point handling by OGR library

[Frank Warmerdam]

Yilmaz Arslanoglu wrote:
> Hi;
> 
> I had some questions regarding the additional feature of sounding
> point handling by the OGR library.
> 
> I know that we need to turn on the options SPLIT_MULTIPOINT and
> ADD_SOUNDG_DEPTH options on.
> 
> 1) Is there a way to turn them individually on without affecting the
> other suboptions in OGR_S57_OPTIONS ?
>     Because if we do it by the following statement:
> 
>    CPLSetConfigOption("OGR_S57_OPTIONS",
> "SPLIT_MULTIPOINT=ON,ADD_SOUNDG_DEPTH=ON");
> 
>    Then there is a possibility to overwrite the other suboptions
> UPDATES, RETURN_PRIMITIVES,
>     PRESERVE_EMPTY_NUMBERS, LNAM_REFS, and RETURN_LINKAGES.

Yilmaz,

You are correct, calling CPLSetConfigOption() will clear the previous
setting, so if you want things amalgamated you need to do it
yourself in code in some fashion.

> 2) With turning ADD_SOUNDG_DEPTH option on, the points become three
> dimensional, where the Z
>     member variable contains the retrieved depth value I guess. Here,
> my question is, does this depth
>     retrieval process take care of any unit conversions (meters,
> fathoms, feet, etc.) ?

I do not believe it is doing any unit conversion.  You will
get a Z coordinate in the depth units that it appears in
the depth attribute.

In general OGR and OGRSpatialReference do not attempt to
address the units of Z values even though there is an OGC
coverage of compound (ie. 2D + elevation) coordinate systems.

Best regards,
-- 
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