| Internet-Draft | A YANG Grouping for Geographic Locations | December 2020 |
| Hopps | Expires 5 June 2021 | [Page] |
This document defines a generic geographical location object YANG grouping. The geographical location grouping is intended to be used in YANG models for specifying a location on or in reference to Earth or any other astronomical object.¶
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Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.¶
In many applications we would like to specify the location of something geographically. Some examples of locations in networking might be the location of data center, a rack in an internet exchange point, a router, a firewall, a port on some device, or it could be the endpoints of a fiber, or perhaps the failure point along a fiber.¶
Additionally, while this location is typically relative to Earth, it does not need to be. Indeed it is easy to imagine a network or device located on The Moon, on Mars, on Enceladus (the moon of Saturn) or even a comet (e.g., 67p/churyumov-gerasimenko).¶
Finally, one can imagine defining locations using different frames of reference or even alternate systems (e.g., simulations or virtual realities).¶
This document defines a geo-location YANG grouping that allows for
all of the above data to be captured.¶
This specification conforms to [ISO.6709.2008].¶
The YANG data model described in this document conforms to the Network Management Datastore Architecture defined in [RFC8342].¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
The frame of reference (reference-frame) defines what the
location values refer to and their meaning. The referred to
object can be any astronomical body. It could be a planet such as
Earth or Mars, a moon such as Enceladus, an asteroid such as
Ceres, or even a comet such as 1P/Halley. This value is specified
in astronomical-body and is defined by the International
Astronomical Union. The default astronomical-body value is
earth.¶
In addition to identifying the astronomical body we also need to
define the meaning of the coordinates (e.g., latitude and
longitude) and the definition of 0-height. This is done with a
geodetic-datum value. The default value for geodetic-datum is
wgs-84 (i.e., the World Geodetic System, [WGS84]), which is used
by the Global Positioning System (GPS) among many others. We
define an IANA registry for specifying standard values for the
geodetic-datum.¶
In addition to the geodetic-datum value we allow refining the
coordinate and height accuracy using coord-accuracy and
height-accuracy respectively. When specified these values
override the defaults implied by the geodetic-datum value.¶
Finally, we define an optional feature which allows for changing
the system for which the above values are defined. This optional
feature adds an alternate-system value to the reference frame.
This value is normally not present which implies the natural
universe is the system. The use of this value is intended to
allow for creating virtual realities or perhaps alternate
coordinate systems. The definition of alternate systems is
outside the scope of this document.¶
This is the location on or relative to the astronomical object.
It is specified using 2 or 3 coordinates values. These values are
given either as latitude, longitude, and an optional
height, or as Cartesian coordinates of x, y and z. For
the standard location choice latitude and longitude are
specified as fractions of decimal degrees, and the height value
is in fractions of meters. For the Cartesian choice x, y and
z are in fractions of meters. In both choices the exact
meanings of all of the values are defined by the geodetic-datum
value in the Section 2.1.¶
Support is added for objects in relatively stable motion. For
objects in relatively stable motion the grouping provides a
3-dimensional vector value. The components of the vector are
v-north, v-east and v-up which are all given in fractional
meters per second. The values v-north and v-east are relative
to true-north as defined by the reference frame for the
astronomical body, v-up is perpendicular to the plane defined
by v-north and v-east, and is pointed away from the center of
mass.¶
To derive the 2-dimensional heading and speed one would use the following formulas:¶
,------------------------------
speed = V v_{north}^{2} + v_{east}^{2}
heading = arctan(v_{east} / v_{north})
¶
For some applications that demand high accuracy, and where the data is infrequently updated this velocity vector can track very slow movement such as continental drift.¶
Tracking more complex forms of motion is outside the scope of this work. The intent of the grouping being defined here is to identify where something is located, and generally this is expected to be somewhere on or relative to Earth (or another astronomical body). At least two options are available to YANG models that wish to use this grouping with objects that are changing location frequently in non-simple ways, they can add additional motion data to their model directly, or if the application allows it can require more frequent queries to keep the location data current.¶
When locations are nested (e.g., a building may have a location
which houses routers that also have locations) the module using
this grouping is free to indicate in its definition that the
reference-frame is inherited from the containing object so that
the reference-frame need not be repeated in every instance of
location data.¶
During the development of this module, the question of whether it would support data such as orientation arose. These types of attributes are outside the scope of this grouping because they do not deal with a location but rather describe something more about the object that is at the location. Module authors are free to add these non-location attributes along with their use of this location grouping.¶
The following is the YANG tree diagram [RFC8340] for the geo-location grouping.¶
module: ietf-geo-location
grouping geo-location
+-- geo-location
+-- reference-frame
| +-- alternate-system? string {alternate-systems}?
| +-- astronomical-body? string
| +-- geodetic-system
| +-- geodetic-datum? string
| +-- coord-accuracy? decimal64
| +-- height-accuracy? decimal64
+-- (location)?
| +--:(ellipsoid)
| | +-- latitude? decimal64
| | +-- longitude? decimal64
| | +-- height? decimal64
| +--:(cartesian)
| +-- x? decimal64
| +-- y? decimal64
| +-- z? decimal64
+-- velocity
| +-- v-north? decimal64
| +-- v-east? decimal64
| +-- v-up? decimal64
+-- timestamp? yang:date-and-time
+-- valid-until? yang:date-and-time
¶
This model imports Common YANG Data Types [RFC6991]. It uses YANG version 1.1 [RFC7950]¶
<CODE BEGINS> file "ietf-geo-location@2019-02-17.yang"
module ietf-geo-location {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-geo-location";
prefix geo;
import ietf-yang-types {
prefix yang;
reference "RFC 6991: Common YANG Data Types.";
}
organization
"IETF NETMOD Working Group (NETMOD)";
contact
"Christian Hopps <chopps@chopps.org>";
// RFC Ed.: replace XXXX with actual RFC number or IANA reference
// and remove this note.
description
"This module defines a grouping of a container object for
specifying a location on or around an astronomical object (e.g.,
'earth').
Copyright (c) 2019 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
for full legal notices.
// RFC Ed.: replace XXXX with the actual RFC number or IANA
// reference and remove this note.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.";
revision 2019-02-17 {
description "Initial Revision";
reference "RFC XXXX: A YANG Grouping for Geographic Locations";
}
feature alternate-systems {
description
"This feature means the device supports specifying locations
using alternate systems for reference frames.";
}
grouping geo-location {
description
"Grouping to identify a location on an astronomical object.";
container geo-location {
description
"A location on an astronomical body (e.g., 'earth')
somewhere in a universe.";
container reference-frame {
description
"The Frame of Reference for the location values.";
leaf alternate-system {
if-feature alternate-systems;
type string;
description
"The system in which the astronomical body and
geodetic-datum is defined. Normally, this value is not
present and the system is the natural universe; however,
when present this value allows for specifying alternate
systems (e.g., virtual realities). An alternate-system
modifies the definition (but not the type) of the other
values in the reference frame.";
}
leaf astronomical-body {
type string {
pattern '[ -@\[-\^_-~]*';
}
default "earth";
description
"An astronomical body as named by the International
Astronomical Union (IAU) or according to the alternate
system if specified. Examples include 'sun' (our star),
'earth' (our planet), 'moon' (our moon), 'enceladus' (a
moon of Saturn), 'ceres' (an asteroid),
'67p/churyumov-gerasimenko (a comet). The value should
be comprised of all lower case ASCII characters not
including control characters (i.e., values 32..64, and
91..126). Any preceding 'the' in the name should not be
included.";
reference "https://www.iau.org/";
}
container geodetic-system {
description
"The geodetic system of the location data.";
leaf geodetic-datum {
type string {
pattern '[ -@\[-\^_-~]*';
}
default "wgs-84";
description
"A geodetic-datum defining the meaning of latitude,
longitude and height. The default is 'wgs-84' which is
used by the Global Positioning System (GPS). The value
SHOULD be comprised of all lower case ASCII characters
not including control characters (i.e., values 32..64,
and 91..126). The IANA registry further restricts the
value by converting all spaces (' ') to dashes ('-')";
reference
"IANA XXXX YANG Geographic Location Parameters,
Geodetic System Values";
}
leaf coord-accuracy {
type decimal64 {
fraction-digits 6;
}
description
"The accuracy of the latitude longitude pair for
ellipsoidal coordinates, or the X, Y and Z components
for Cartesian coordinates. When coord-accuracy is
specified it overrides the geodetic-datum implied
accuracy.";
}
leaf height-accuracy {
type decimal64 {
fraction-digits 6;
}
units "meters";
description
"The accuracy of height value for ellipsoidal
coordinates, this value is not used with Cartesian
coordinates. When specified it overrides the
geodetic-datum implied default.";
}
}
}
choice location {
description
"The location data either in lat/long or Cartesian values";
case ellipsoid {
leaf latitude {
type decimal64 {
fraction-digits 16;
}
units "decimal degrees";
description
"The latitude value on the astronomical body. The
definition and precision of this measurement is
indicated by the reference-frame value.";
}
leaf longitude {
type decimal64 {
fraction-digits 16;
}
units "decimal degrees";
description
"The longitude value on the astronomical body. The
definition and precision of this measurement is
indicated by the reference-frame.";
}
leaf height {
type decimal64 {
fraction-digits 6;
}
units "meters";
description
"Height from a reference 0 value. The precision and '0'
value is defined by the reference-frame.";
}
}
case cartesian {
leaf x {
type decimal64 {
fraction-digits 6;
}
units "meters";
description
"The X value as defined by the reference-frame.";
}
leaf y {
type decimal64 {
fraction-digits 6;
}
units "meters";
description
"The Y value as defined by the reference-frame.";
}
leaf z {
type decimal64 {
fraction-digits 6;
}
units "meters";
description
"The Z value as defined by the reference-frame.";
}
}
}
container velocity {
description
"If the object is in motion the velocity vector describes
this motion at the the time given by the timestamp. For a
formula to convert these values to speed and heading see
this modules defining document RFC XXXX.";
reference
"RFC XXXX: A YANG Grouping for Geographic Locations";
leaf v-north {
type decimal64 {
fraction-digits 12;
}
units "meters per second";
description
"v-north is the rate of change (i.e., speed) towards
truth north as defined by the geodetic-system.";
}
leaf v-east {
type decimal64 {
fraction-digits 12;
}
units "meters per second";
description
"v-east is the rate of change (i.e., speed) perpendicular
to truth-north as defined by the geodetic-system.";
}
leaf v-up {
type decimal64 {
fraction-digits 12;
}
units "meters per second";
description
"v-up is the rate of change (i.e., speed) away from the
center of mass.";
}
}
leaf timestamp {
type yang:date-and-time;
description "Reference time when location was recorded.";
}
leaf valid-until {
type yang:date-and-time;
description
"The timestamp for which this geo-location is valid until.
If unspecified the geo-location has no specific expiration
time.";
}
}
}
}
<CODE ENDS>
¶
[ISO.6709.2008] provides an appendix with a set of tests for conformance to the standard. The tests and results are given in the following table along with an explanation of non-applicable tests.¶
| Test | Description | Pass Explanation |
|---|---|---|
| A.1.2.1 | elements reqd. for a geo. point location | CRS is always indicated |
| A.1.2.2 | Description of a CRS from a register | CRS register is defined |
| A.1.2.3 | definition of CRS | N/A - Don't define CRS |
| A.1.2.4 | representation of horizontal position | lat/long values conform |
| A.1.2.5 | representation of vertical position | height value conforms |
| A.1.2.6 | text string representation | N/A - No string format |
For test A.1.2.1 the YANG geo location object either includes a CRS
(reference-frame) or has a default defined ([WGS84]).¶
For A.1.2.3 we do not define our own CRS, and doing so is not
required for conformance.¶
For A.1.2.6 we do not define a text string representation, which is
also not required for conformance.¶
The geo-location object defined in this document and YANG module have been designed to be usable in a very broad set of applications. This includes the ability to locate things on astronomical bodies other than Earth, and to utilize entirely different coordinate systems and realities.¶
Many systems make use of geo-location data, and so it's important to be able describe this data using this geo-location object defined in this document.¶
In order to verify portability while developing this module the following standards and standard APIs and were considered.¶
[RFC5870] defines a standard URI value for geographic location data. It
includes the ability to specify the geodetic-value (it calls this
crs) with the default being wgs-84 [WGS84]. For the location data
it allows 2 to 3 coordinates defined by the crs value. For accuracy
it has a single u parameter for specifying uncertainty. The u
value is in fractions of meters and applies to all the location
values. As the URI is a string, all values are specifies as strings
and so are capable of as much precision as required.¶
URI values can be mapped to and from the YANG grouping, with the caveat that some loss of precision (in the extremes) may occur due to the YANG grouping using decimal64 values rather than strings.¶
W3C Defines a geo-location API in [W3CGEO]. We show a snippet of code below which defines the geo-location data for this API. This is used by many application (e.g., Google Maps API).¶
interface GeolocationPosition {
readonly attribute GeolocationCoordinates coords;
readonly attribute DOMTimeStamp timestamp;
};
interface GeolocationCoordinates {
readonly attribute double latitude;
readonly attribute double longitude;
readonly attribute double? altitude;
readonly attribute double accuracy;
readonly attribute double? altitudeAccuracy;
readonly attribute double? speed;
};
| Field | Type | YANG | Type |
|---|---|---|---|
| accuracy | double | coord-accuracy | dec64 fr 6 |
| altitude | double | height | dec64 fr 6 |
| altitudeAccuracy | double | height-accuracy | dec64 fr 6 |
| heading | double | v-north, v-east | dec64 fr 12 |
| latitude | double | latitude | dec64 fr 16 |
| longitude | double | longitude | dec64 fr 16 |
| speed | double | v-north, v-east | dec64 fr 12 |
| timestamp | DOMTimeStamp | timestamp | string |
Accuracy of latitude and longitude values
in meters.¶
Optional accuracy of altitude value
in meters.¶
Optional Direction in decimal deg from true north increasing clock-wise.¶
Standard lat/long values in decimal degrees.¶
Speed along heading in meters per second.¶
Specifies milliseconds since the Unix EPOCH in 64 bit unsigned integer. The YANG model defines the timestamp with arbitrarily large precision by using a string which encompasses all representable values of this timestamp value.¶
W3C API values can be mapped to the YANG grouping, with the caveat that some loss of precision (in the extremes) may occur due to the YANG grouping using decimal64 values rather than doubles.¶
Conversely, only YANG values for Earth using the default
wgs-84 [WGS84] as the geodetic-datum, can be directly mapped to the
W3C values, as W3C does not provide the extra features necessary to
map the broader set of values supported by the YANG grouping.¶
ISO adopted the Geography Markup Language (GML) defined by OGC 07-036
as [ISO.19136.2007]. GML defines, among many other things, a position
type gml:pos which is a sequence of double values. This sequence
of values represent coordinates in a given CRS. The CRS is either
inherited from containing elements or directly specified as
attributes srsName and optionally srsDimension on the gml:pos.¶
GML defines an Abstract CRS type which Concrete CRS types derive from. This allows for many types of CRS definitions. We are concerned with the Geodetic CRS type which can have either ellipsoidal or Cartesian coordinates. We believe that other non-Earth based CRS as well as virtual CRS should also be representable by the GML CRS types as well.¶
Thus GML gml:pos values can be mapped directly to the YANG
grouping, with the caveat that some loss of precision (in the
extremes) may occur due to the YANG grouping using decimal64 values
rather than doubles.¶
Conversely, YANG grouping values can be mapped to GML as directly as the GML CRS available definitions allow with a minimum of Earth-based geodetic systems fully supported.¶
GML also defines an observation value in gml:Observation which
includes a timestamp value gml:validTime in addition to other
components such as gml:using gml:target and gml:resultOf. Only
the timestamp is mappable to and from the YANG grouping. Furthermore
gml:validTime can either be an Instantaneous measure
(gml:TimeInstant) or a time period (gml:TimePeriod). The
instantaneous gml:TimeInstant is mappable to and from the YANG
grouping timestamp value, and values down to the resolution of
seconds for gml:TimePeriod can be mapped using the valid-until
node of the YANG grouping.¶
KML 2.2 [KML22] (formerly Keyhole Markup Language) was submitted by
Google to the Open Geospatial Consortium, and was adopted. The latest
version as of this writing is KML 2.3 [KML23]. This schema includes
geographic location data in some of its objects (e.g., kml:Point or
kml:Camera objects). This data is provided in string format and
corresponds to the [W3CGEO] values. The timestamp value is also
specified as a string as in our YANG grouping.¶
KML has some special handling for the height value useful for
visualization software, kml:altitudeMode. These values for
kml:altitudeMode include indicating the height is ignored
(clampToGround), in relation to the location's ground level
(relativeToGround), or in relation to the geodetic datum
(absolute). The YANG grouping can directly map the ignored and
absolute cases, but not the relative to ground case.¶
In addition to the kml:altitudeMode KML also defines two seafloor
height values using kml:seaFloorAltitudeMode. One value is to
ignore the height value (clampToSeaFloor) and the other is relative
(relativeToSeaFloor). As with the kml:altitudeMode value, the
YANG grouping supports the ignore case but not the relative case.¶
The KML location values use a geodetic datum defined in Annex A by
the GML Coordinate Reference System (CRS) [ISO.19136.2007] with
identifier LonLat84_5773. The altitude value for KML absolute
height mode is measured from the vertical datum specified by [WGS84].¶
Thus the YANG grouping and KML values can be directly mapped in both directions (when using a supported altitude mode) with the caveat that some loss of precision (in the extremes) may occur due to the YANG grouping using decimal64 values rather than strings. For the relative height cases the application doing the transformation is expected to have the data available to transform the relative height into an absolute height which can then be expressed using the YANG grouping.¶
IANA is asked to create a new registry "Geodetic System Values" under a new protocol category group "YANG Geographic Location Parameters".¶
This registry allocates names for standard geodetic systems. Often these values are referred to using multiple names (e.g., full names or multiple acronyms values). The intent of this registry is to provide a single standard value for any given geodetic system.¶
The values SHOULD use an acronym when available, they MUST be converted to lower case, and spaces MUST be changed to dashes "-".¶
Each entry should be sufficient to define the 3 coordinate values (2
if height is not required). So for example the wgs-84 is defined as
WGS-84 with the geoid updated by at least [EGM96] for height values.
Specific entries for [EGM96] and [EGM08] are present if a more precise
definition of the data is required.¶
It should be noted that [RFC5870] also creates a registry for Geodetic Systems (it calls CRS); however, this registry has a very strict modification policy. The authors of [RFC5870] have the stated goal of making CRS registration hard to avoid proliferation of CRS values. As our module defines alternate systems and has a broader (beyond Earth) scope, the registry defined below is meant to be more easily modified.¶
The allocation policy for this registry is First Come First Served, [RFC8126] as the intent is simply to avoid duplicate values.¶
The initial values for this registry are as follows.¶
| Name | Description |
|---|---|
| me | Mean Earth/Polar Axis (Moon) |
| mola-vik-1 | MOLA Height, IAU Viking-1 PM (Mars) |
| wgs-84-96 | World Geodetic System 1984 [WGS84] w/ EGM96 |
| wgs-84-08 | World Geodetic System 1984 [WGS84] w/ [EGM08] |
| wgs-84 | World Geodetic System 1984 [WGS84] (EGM96 or better) |
This document registers a URI in the "IETF XML Registry" [RFC3688]. Following the format in [RFC3688], the following registration has been made:¶
This document registers one YANG module in the "YANG Module Names" registry [RFC6020]. Following the format in [RFC6020], the following registration has been made:¶
The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446].¶
The NETCONF access control model [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content.¶
Since the modules defined in this document only define groupings, these considerations are primarily for the designers of other modules that use these groupings.¶
All of the data nodes defined in this YANG module are writable/creatable/deletable (i.e., "config true", which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. These are the subtrees and data nodes and their sensitivity/vulnerability:¶
None of the writable/creatable/deletable data nodes in the YANG module defined in this document are by themselves considered more sensitive or vulnerable then standard configuration.¶
Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. These are the subtrees and data nodes and their sensitivity/vulnerability:¶
Since the grouping defined in this module identifies locations, authors using this grouping SHOULD consider any privacy issues that may arise when the data is readable.¶
This document does not define any RPC actions and hence this section does not consider the security of RPCs.¶
Below is a fictitious module that uses the geo-location grouping.¶
module example-uses-geo-location {
namespace
"urn:example:example-uses-geo-location";
prefix ugeo;
import ietf-geo-location { prefix geo; }
organization "Empty Org";
contact "Example Author <eauthor@example.com>";
description "Example use of geo-location";
revision 2019-02-02 { reference "None"; }
container locatable-items {
description "container of locatable items";
list locatable-item {
key name;
description "A of locatable item";
leaf name {
type string;
description "name of locatable item";
}
uses geo:geo-location;
}
}
}
Below is a the YANG tree for the fictitious module that uses the geo-location grouping.¶
module: example-uses-geo-location
+--rw locatable-items
+--rw locatable-item* [name]
+--rw name string
+--rw geo-location
+--rw reference-frame
| +--rw alternate-system? string {alternate-systems}?
| +--rw astronomical-body? string
| +--rw geodetic-system
| +--rw geodetic-datum? string
| +--rw coord-accuracy? decimal64
| +--rw height-accuracy? decimal64
+--rw (location)?
| +--:(ellipsoid)
| | +--rw latitude? decimal64
| | +--rw longitude? decimal64
| | +--rw height? decimal64
| +--:(cartesian)
| +--rw x? decimal64
| +--rw y? decimal64
| +--rw z? decimal64
+--rw velocity
| +--rw v-north? decimal64
| +--rw v-east? decimal64
| +--rw v-up? decimal64
+--rw timestamp? yang:date-and-time
+--rw valid-until? yang:date-and-time
¶
Below is some example YANG XML data for the fictitious module that uses the geo-location grouping.¶
<locatable-items xmlns="urn:example:example-uses-geo-location">
<locatable-item>
<name>Gaetana's</name>
<geo-location>
<latitude>40.73297</latitude>
<longitude>-74.007696</longitude>
</geo-location>
</locatable-item>
<locatable-item>
<name>Pont des Arts</name>
<geo-location>
<timestamp>2012-03-31T16:00:00Z</timestamp>
<latitude>48.8583424</latitude>
<longitude>2.3375084</longitude>
<height>35</height>
</geo-location>
</locatable-item>
<locatable-item>
<name>Saint Louis Cathedral</name>
<geo-location>
<timestamp>2013-10-12T15:00:00-06:00</timestamp>
<latitude>29.9579735</latitude>
<longitude>-90.0637281</longitude>
</geo-location>
</locatable-item>
<locatable-item>
<name>Apollo 11 Landing Site</name>
<geo-location>
<timestamp>1969-07-21T02:56:15Z</timestamp>
<reference-frame>
<astronomical-body>moon</astronomical-body>
<geodetic-system>
<geodetic-datum>me</geodetic-datum>
</geodetic-system>
</reference-frame>
<latitude>0.67409</latitude>
<longitude>23.47298</longitude>
</geo-location>
</locatable-item>
<locatable-item>
<name>Reference Frame Only</name>
<geo-location>
<reference-frame>
<astronomical-body>moon</astronomical-body>
<geodetic-system>
<geodetic-datum>me</geodetic-datum>
</geodetic-system>
</reference-frame>
</geo-location>
</locatable-item>
</locatable-items>
We would like to thank Jim Biard and Ben Koziol for their reviews and suggested improvements. We would also like to thank Peter Lothberg for the motivation as well as help in defining a broadly useful geographic location object, and Acee Lindem and Qin Wu for their work on a geographic location object that led to this documents creation.¶