[Esip-documentation] geospatial_bounds: how to show 3-D bbox?

Tue Jan 24 14:17:12 EST 2017

Thanks, Ted. But there are two discussions going on here that I think you
are conflating. 1) How to represent a 3D bounding box in WKT. 2) The
coordinate order. Irrespective of #1, the coordinate order depends on the
specified CRS, as I just explained. And it seems nobody has any suggestions
on how to do #1, so I'll just be ignoring the z dimension and focusing on
2D POLYGONs in my geospatial_bounds. (Plus, the end user/software already
has *_min/*_max values for all dimensions anyhow.) I believe the proper way
to do #1 is with a POLYHEDRALSURFACE, but I find that overly verbose (and
likely unsupported in some software). Unfortunately, the more succinct
ENVELOPE representation is not part of the WKT spec.
Cheers,
John

On Tue, Jan 24, 2017 at 8:55 AM, Ted Habermann <thabermann at hdfgroup.org>
wrote:

> John et al.,
>
> I think that for a 3D object we will need a 3D coordinate system (seems
> obvious). I am not sure about the coordinate order, I.e. The order of the
> points…
>
> Ted
>
> ==== Ted Habermann ========================
> Director of Earth Science, The HDF Group
> Voice: (217) 531-4202
> Email: thabermann at hdfgroup.org
> ==== HDF: Software That Powers Science ====
>
> From: Esip-documentation <esip-documentation-bounces at lists.esipfed.org>
> on behalf of "esip-documentation at lists.esipfed.org" <
> esip-documentation at lists.esipfed.org>
> Reply-To: John Maurer <jmaurer at hawaii.edu>
> Date: Tuesday, January 24, 2017 at 11:47 AM
> To: Anna Milan <anna.milan at noaa.gov>
> Cc: "esip-documentation at lists.esipfed.org" <esip-documentation at lists.
> esipfed.org>
> Subject: Re: [Esip-documentation] geospatial_bounds: how to show 3-D bbox?
>
> Actually, I believe there is more to this topic. The spec says the order
> should follow the CRS given*. For EPSG:4326
> <http://spatialreference.org/ref/epsg/wgs-84/>, the order is lon lat. For
> CRS:84, the order is lat lon. Yes, confusing, but stuck that way for legacy
> reasons. So, I believe it depends on geospatial_bounds_crs. In my case (and
> in many cases, I'm guessing, including the ACDD default), I'm setting
> geospatial_bounds_crs to ESPG:4326, so I believe I (and your wiki example)
> should use lon lat order in geospatial_bounds. This also trips up people a
> lot in WMS 1.3.0 requests, where lon lat order switches between EPSG:4326
> and CRS:84 (one example
> <https://viswaug.wordpress.com/2009/03/15/reversed-co-ordinate-axis-order-for-epsg4326-vs-crs84-when-requesting-wms-130-images/>).
> Thoughts?
> Cheers,
> John
>
> * http://docs.opengeospatial.org/is/12-063r5/12-063r5.html#41
>
>> If <axis order> is omitted from the WKT string the sequence of <axis>
>> descriptions shall imply the order of the axes and of coordinates
>> referenced to the CRS.
>>
>
> On Tue, Jan 24, 2017 at 8:10 AM, Anna Milan - NOAA Federal via
> Esip-documentation <esip-documentation at lists.esipfed.org> wrote:
>
>> So - I should NOT change the order in the wiki example?
>>
>> Anna
>> *~~~~~~Metadata Adds Meaning~~~~~~*
>> Anna.Milan at noaa.gov, 303-497-5099 <(303)%20497-5099>
>> NOAA National Centers for Environmental Information
>> (formerly NOAA’s National Geophysical Data Center)
>> http://www.ngdc.noaa.gov/metadata/emma
>> *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*
>>
>> On Tue, Jan 24, 2017 at 7:50 AM, Jim Biard via Esip-documentation <
>> esip-documentation at lists.esipfed.org> wrote:
>>
>>> Sadly (to me, at any rate), the official EPSG/OGC/WKT definition for
>>> latitude longitude order is lat before lon. It's left-handed and drives me
>>> insane every time, but apparently the historical definition from way back
>>> is lat before lon. It makes regular headaches for people that need to
>>> accomodate both projected and geodetic coordinates, but it is what it is.
>>>
>>> Here's a discussion - http://lists.osgeo.org/piperma
>>> il/postgis-users/2015-November/040971.html
>>>
>>> Grace and peace,
>>>
>>> Jim
>>>
>>> On 1/23/17 10:10 PM, John Maurer via Esip-documentation wrote:
>>>
>>> P.S. Your POLYGON example for geospatial_bounds on the following page
>>> has latitudes and longitudes in the wrong order. Instead of listing
>>> coordinate pairs in lat, lon (y, x) order they should be lon, lat (x, y).
>>>
>>> http://wiki.esipfed.org/index.php/Attribute_Convention_for_D
>>> ata_Discovery_1-3
>>>
>>> Example: 'POLYGON ((40.26 -111.29, 41.26 -111.29, 41.26 -110.29, 40.26
>>>> -110.29, 40.26 -111.29))'.
>>>>
>>>
>>> Should be:
>>>
>>> Example: 'POLYGON ((-111.29 40.26, -111.29 41.26, -110.29 41.26, -110.29
>>>> 40.26, -111.29 40.26))'.
>>>>
>>>
>>> Thanks,
>>> John
>>>
>>> On Mon, Jan 23, 2017 at 4:32 PM, John Maurer <jmaurer at hawaii.edu> wrote:
>>>
>>>> Hi ACDD folks,
>>>> Can somebody please provide an example of the Well-Known Text (WKT)
>>>> that could be used to represent a 3-D bounding box for the ACDD
>>>> "geospatial_bounds" attribute? Let's say I have the following bounds
>>>> defined for a global digital elevation model (DEM):
>>>>
>>>> geospatial_lat_min: -90
>>>> geospatial_lat_max: 90
>>>> geospatial_lon_min: -180
>>>> geospatial_lon_max: 180
>>>> geospatial_vertical_min: 0
>>>> geospatial_vertical_max: 1000
>>>>
>>>> Would this cube be expressed in WKT as a "POLYHEDRALSURFACE Z( )", a
>>>> "POLYGON Z( )", or does WKT recognize "ENVELOPE Z( )"? Either way, can an
>>>> example please be provided? Google has not been very helpful beyond the
>>>> simpler POINT and POLYGON representations.
>>>>
>>>> It seems outlandish to provide a POLYHEDRALSURFACE, which ends up as
>>>> verbose as the following example. This is for a cube with origin at (0, 0,
>>>> 0) and opposite corner at (1, 1, 1):
>>>>
>>>> POLYHEDRALSURFACE Z (
>>>>   ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
>>>>   ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
>>>>   ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
>>>>   ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
>>>>   ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
>>>>   ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
>>>> )
>>>>
>>>> Thoughts?
>>>> Thanks!,
>>>> John Maurer
>>>> Pacific Islands Ocean Observing System (PacIOOS)
>>>> University of Hawaii at Manoa
>>>>
>>>> P.S. It seems a tad redundant to have both the *_min/*_max attributes
>>>> and the geospatial_bounds.
>>>>
>>>>
>>>
>>>
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