[Gdal-dev] Problems retrieving z-values

[Frank Warmerdam]

On 9/26/07, tjansson <tommy.jansson at kongsberg.com> wrote:
>
> I am writing a library which reads S-57 files (of type *.000) and loads
> selected geometies into a custom class structure. The files are read and
> content handled using the OGR Simple Features Library for C++.
>
> As far as I have understood the various geometries are divided into two
> categories; 2D geometry types with XY-data, and 2.5D geometry XYZ-data.
>
> I am interested in geometries of type 2.5D (i.e with XYZ-data). In my code
> there is a function which parses geometry objects using a switch that check
> the geometry type (and handles it accordingly). I have read several maps
> with success (e.g. downloaded from NOAA), except that the Z-value is always
> set to 0 (zero). I've also noticed - when debugging - that the switch never
> hits on geometry type "wkbPoint25D" (or any other 2.5D type), which might
> explain the Z-value.
>
> Is the code i have written doing something wrong, because I never get a hit
> on any 2.5D types, or are the maps I have downloaded the cause (because they
> don't contain any 2.5D types)?

Tommy,

I think SOUNDG features the the main feature type in S-57
that actually returns 3D geometries, and they are normally
of type wkbMultiPoint25D.

I *think* (memory grows foggy) that most other geometries
you would think might be 2.5D - like depth polygons - just
keep the depth as an attribute.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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