[Esip-documentation] Geospatial Bounds

John Graybeal via Esip-documentation esip-documentation at lists.esipfed.org
Wed Oct 1 13:44:10 EDT 2014


Aleksander,

Thanks for the timely update (and the reassuring acknowledgment that the meeting is tomorrow!).

I've put this content into the Active Issues spreadsheet and optimistically marked the thread 'Resolved pending review', which is true at the moment anyway. :-)  

I did have a few simple questions.

1) Do I correctly understand that the height of EPSG 4979 is GPS height, that is, above the ellipsoid that GPS uses?
2) If it's really true that the ranges of the geospatial limits are approximate values (first I've heard that), shouldn't we say that in their definitions?
3) DId you mean to say this attribute must always use this vertical datum?  Or just that this is the default?

I'm OK with it if people want this attribute to always use ellipsoidal height, but I suspect many applications will only have the height above/below the actual surface (for example, Instantaneous Water Level, EPSG 5113). I am wondering if there is a simple way to allow the alternative datum to be specified.

John


On Oct 1, 2014, at 09:59, Aleksandar Jelenak via Esip-documentation <esip-documentation at lists.esipfed.org> wrote:

> Dear all,
> 
> Just in time for today’s meeting, below is the latest version of the
> geospatial_bounds definition:
> 
> Describes geospatial extent using geometric objects (2D or 3D) defined in
> the Well-Known Text (WKT) format. geospatial_bounds points are always
> space-separated latitude (decimal degrees_north), longitude (decimal
> degrees_east), and, for 3D objects, altitude (meters, up) values of the
> WGS-84 coordinate reference system. Specifically WGS-84 (EPSG:4326) for 2D
> objects and WGS-84 (EPSG:4979) for 3D objects. Like the
> geospatial_lon/lat_min/max attributes, these are typically approximate
> values. Note that longitude values are not restricted to the [-180, 180]
> range only. Example: "POLYGON ((40.26 -111.29, 41.26 -111.29, 41.26
> -110.29, 40.26 -110.29, 40.26 -111.29))".
> 
> 
> 
> I hope the text now satisfies all the raised issues.
> 
> 	-Aleksandar
> 
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