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

Tue Jan 24 13:55:18 EST 2017

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

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From: Esip-documentation <esip-documentation-bounces at lists.esipfed.org<mailto:esip-documentation-bounces at lists.esipfed.org>> on behalf of "esip-documentation at lists.esipfed.org<mailto:esip-documentation at lists.esipfed.org>" <esip-documentation at lists.esipfed.org<mailto:esip-documentation at lists.esipfed.org>>
Reply-To: John Maurer <jmaurer at hawaii.edu<mailto:jmaurer at hawaii.edu>>
Date: Tuesday, January 24, 2017 at 11:47 AM
To: Anna Milan <anna.milan at noaa.gov<mailto:anna.milan at noaa.gov>>
Cc: "esip-documentation at lists.esipfed.org<mailto:esip-documentation at lists.esipfed.org>" <esip-documentation at lists.esipfed.org<mailto: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<mailto:esip-documentation at lists.esipfed.org>> wrote:
So - I should NOT change the order in the wiki example?

Anna
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On Tue, Jan 24, 2017 at 7:50 AM, Jim Biard via Esip-documentation <esip-documentation at lists.esipfed.org<mailto: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/pipermail/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_Data_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<mailto: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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