Hi.
NAVD88 is a geoid adjusted to geodetic leveling measurements taken all over North America and fixed to the ?mean sea level? height at Rimouski, Quebec, Canada. (
http://en.wikipedia.org/wiki/North_American_Vertical_Datum_of_1988)
Jim
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On Feb 6, 2014, at 11:47 AM, Jonathan Gregory <j.m.gregory at reading.ac.uk> wrote:
> Dear Rich
>
>> Yes, I think your answer before is the answer now, but I'm just clear
>> on the details. Would you specify sea_surface_height above NAVD88
>> like this?
>>
>> float zeta(y=1534, x=2122);
>> :standard_name = "sea_surface_height_above_reference_datum";
>> :grid_mapping = "Albers_Projection";
>>
>> int Albers_Projection;
>> :grid_mapping_name = "albers_conical_equal_area";
>> :standard_parallel = 20.5, 27.5; // double
>> :longitude_of_central_meridian = -89.0; // double
>> :latitude_of_projection_origin = 24.0; // double
>> :false_easting = 0.0; // double
>> :false_north = 0.0; // double
>> :vertical_datum = 'urn:ogc:def:datum:epsg::5103'
>
> I'm not clear still what NAVD88 is though. SSH must be above some surface. Is
> this surface a reference ellipsoid or a geoid? These are two different standard
> names:
> sea_surface_height_above_geoid
> sea_surface_height_above_reference_ellipsoid
> whereas sea_surface_height_above_reference_datum is not an existing stdname.
>
> If it's a reference ellipsoid, it can be described already by grid_mapping
> parameters. To name a geoid, we'd need a new attribute of grid_mapping, but
> I don't think that would be problematic.
>
> Best wishes
>
> Jonathan
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Received on Fri Feb 07 2014 - 08:19:16 GMT
