Subject: [Geopriv] Fw: New Version Notification for draft-mayrhofer-geopriv-geo-uri-00

From: "Alexander Mayrhofer" <[email-masked]>
Date: Wed, 21 May 2008 12:31:49 +0200

fyi - i have published an updated version of the "geo" URI idea, renamed
so that it's clear we don't want to "sneak by" the GEOPRIV working
group. We have incorporated feedback, most notably GML mapping
definitions.

I've heard from two implementors that they are definitely interested in
this - i will talk to them whether they can send a note with their use
cases to the list.

The "tiling hierarchy" idea will be published in a seperate document,
potentially before the weekend.

As always, any feedback is appreciated.

thanks

Alex

---
A new version of I-D, draft-mayrhofer-geopriv-geo-uri-00.txt has been
successfuly submitted by Alexander Mayrhofer and posted to the IETF
repository.

Filename:	 draft-mayrhofer-geopriv-geo-uri
Revision:	 00
Title:		 A Uniform Resource Identifier for Geographic Locations
('geo' URI)
Creation_date:	 2008-05-21
WG ID:		 Independent Submission
Number_of_pages: 14

Abstract:
This document specifies an Uniform Resource Identifier (URI) for
geographic locations using the 'geo' scheme name.  A 'geo' URI
provides latitude, longitude and optionally altitude of a physical
location in a compact, simple, human-readable, and protocol
independent way.

The IETF Secretariat.

_______________________________________________
Geopriv mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/geopriv

---

From: "Alexander Mayrhofer" <[email-masked]>
Date: Wed, 21 May 2008 12:41:12 +0200

[i hate answering myself]

> fyi - i have published an updated version of the "geo" URI 
> idea.

i forgot to link to the draft, sorry:

http://www.ietf.org/internet-drafts/draft-mayrhofer-geopriv-geo-uri-00.t
xt

Alex

---

From: "Thomson, Martin" <[email-masked]>
Date: Wed, 21 May 2008 20:10:02 -0500

I've only read through this briefly and it looks good.  I have a few
comments:

This isn't the first time that this has been attempted.  C.f. attempts
to add geo headers to http <it's been discussed in geopriv several
times>, vcard <RFC 2426>.  Simplicity is a virtue, but...

I'm not sure that RFC 3986 allows for a comma in a URI.  It might be
safer to use some other sort of delimiter.

Allowing optional URI parameters would enable metadata to be included.
There is no harm in allowing this in the ABNF.

On invalid URIs, it would be reasonable for a user agent to following
these rules when receiving out of range values:
   - for longitude, wrap the values (e.g. 200 => -160; -300 => 60).
   - for latitude, clamp the values (lat > 90 => 90; lat < -90 => -90).

The OGC/EPSG URNs should be consistent with pdif-lo-profile, which
doesn't include an EPSG version number (i.e. remove the 6.6).

Section 4 shouldn't use sub-headings for each of the URI scheme
registration components.  It took me a while to work out what was going
on.

Cheers,
Martin

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On
> Behalf Of Alexander Mayrhofer
> Sent: Wednesday, 21 May 2008 8:41 PM
> To: Alexander Mayrhofer; GEOPRIV
> Cc: Christian Spanring
> Subject: Re: [Geopriv] Fw: New Version Notificationfordraft-mayrhofer-
> geopriv-geo-uri-00
> 

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---

From: Martin Kofahl <[email-masked]>
Date: Mon, 26 May 2008 14:23:32 +0200

I think it's safe to use a comma in the path segement of an URI (see 
RFC3986 Section 3.3 allowing all sub-delims, defined in Section 2.2). 
Only 'gen-delims' are reserved in the path segment.

Martin

---

From: Martin Kofahl <[email-masked]>
Date: Mon, 26 May 2008 14:23:50 +0200

As there are different types of locations, an identifier would be 
perfect for future use. E.g. similar to RFC2165:

	geo:<identifier>:<location>

	geo:latlon:48.2010,16.3695
	geo:civic:a1=xxx,a2=xxx,country=xx

Martin

---

From: "Carl Reed" <[email-masked]>
Date: Tue, 27 May 2008 12:39:39 -0600

Alex -

Apologies for the delay in providing comments. Hope the following helps.

1. You need to be much more specific about the use of WGS 84. In order to be as clear as possible, I would suggest using the following words:
Geographic locations in this document are defined using WGS 84 (World Geodetic System 1984), equivalent to the OGP Surveying & Positioning Committee EPSG code 4326 (2 dimensions). This document does not assign responsibilities for coordinate transformations from and to other Spatial Reference Systems. A WGS-84 coordinate value is here represented as a comma-delimited latitude/longitude pair, measured in decimal degrees (un-projected). Latitudes range from -90 to 90 and longitudes range from -180 to 180. Coordinates in the Southern and Western hemispheres are signed negative with a leading dash. http://www.epsg.org/ 

There is also now an on-line registry of the EPSG database so the exact parameters for the WGS-84 - 2d datum can be referenced. 

2. I think "altitude" needs to be a bit more clerly and consistently defined. In one place the document mentions "mean sea level" and in another "earth's surface".

3. You might want to check out http://tools.ietf.org/html/draft-daviel-http-geo-header-05 . Similar but different approach to the same problem. For example, the authors of this document do address to a certain extent civic addresses as well as uncertaintly. This document is targeted a bit more at the geo-enabled mobile community.

4. Back to WGS. Might want to mention that WGS stands for World Geodetic System. Also, WGS-84 predates GPS but GPS was used to upgrade WGS-84.

From US National Geodetic Survey: WGS 84 is the World Geodetic System of 1984. It is the reference frame used by the U.S. Department of Defense (DoD) and is defined by the National Geospatial-Intelligence Agency(NGA) (formerly the National Imagery and Mapping Agency) (formerly the Defense Mapping Agency). WGS 84 is used by DoD for all its mapping, charting, surveying, and navigation needs, including its GPS "broadcast" and "precise" orbits. WGS 84 was defined in January 1987 using Doppler satellite surveying techniques. It was used as the reference frame for broadcast GPS Ephemerides (orbits) beginning January 23, 1987. At 0000 GMT January 2, 1994, WGS 84 was upgraded in accuracy using GPS measurements. The formal name then became WGS 84 (G730) since the upgrade date coincided with the start of GPS Week 730. It became the reference frame for broadcast orbits on June 28, 1994. At 0000 GMT September 30, 1996 (the start of GPS Week 873), WGS 84 was redefined again and was more closely aligned with International Earth Rotation Service (IERS) Terrestrial Reference Frame (ITRF) 94. It is now formally called WGS 84 (G873). WGS 84 (G873) was adopted as the reference frame for broadcast orbits on January 29, 1997. 

5. You might also want to check out how geo lat-long are being expressed (proposal) as part of OpenSearch and GeoJSON. http://www.opensearch.org/Specifications/OpenSearch/Extensions/Geo/1.0/Draft_1 . I have concerns that multiple methods of expression are emerging. A killer for interoperability.

Again, I hope this helps!

Regards

Carl Reed

Open Geospatial Consortium

---

From: "Marc Berryman" <[email-masked]>
Date: Tue, 27 May 2008 14:55:52 -0500

Carl,

 Thank you so much for referencing the (proposed) method for expressing
longitude and latitude. I hope everyone takes a minute to review the
OpenSearch.

Marc B 

________________________________

From: [email-masked] [mailto:[email-masked]] On
Behalf Of Carl Reed
Sent: Tuesday, May 27, 2008 1:40 PM
To: Alexander Mayrhofer; GEOPRIV
Cc: Christian Spanring
Subject: Re: [Geopriv] Fw: New
VersionNotificationfordraft-mayrhofer-geopriv-geo-uri-00

Alex -

1. You need to be much more specific about the use of WGS 84. In order
to be as clear as possible, I would suggest using the following words:

Geographic locations in this document are defined using WGS 84 (World
Geodetic System 1984), equivalent to the OGP Surveying & Positioning
Committee EPSG code 4326 (2 dimensions). This document does not assign
responsibilities for coordinate transformations from and to other
Spatial Reference Systems. A WGS-84 coordinate value is here represented
as a comma-delimited latitude/longitude pair, measured in decimal
degrees (un-projected). Latitudes range from -90 to 90 and longitudes
range from -180 to 180. Coordinates in the Southern and Western
hemispheres are signed negative with a leading dash.
http://www.epsg.org/ 

There is also now an on-line registry of the EPSG database so the exact
parameters for the WGS-84 - 2d datum can be referenced. 

2. I think "altitude" needs to be a bit more clerly and consistently
defined. In one place the document mentions "mean sea level" and in
another "earth's surface".

3. You might want to check out
http://tools.ietf.org/html/draft-daviel-http-geo-header-05 . Similar but
different approach to the same problem. For example, the authors of this
document do address to a certain extent civic addresses as well as
uncertaintly. This document is targeted a bit more at the geo-enabled
mobile community.

4. Back to WGS. Might want to mention that WGS stands for World Geodetic
System. Also, WGS-84 predates GPS but GPS was used to upgrade WGS-84.

From US National Geodetic Survey: WGS 84 is the World Geodetic System of
1984. It is the reference frame used by the U.S. Department of Defense
(DoD) and is defined by the National Geospatial-Intelligence Agency(NGA
<http://www.nga.mil/> ) (formerly the National Imagery and Mapping
Agency) (formerly the Defense Mapping Agency). WGS 84 is used by DoD for
all its mapping, charting, surveying, and navigation needs, including
its GPS "broadcast" and "precise" orbits. WGS 84 was defined in January
1987 using Doppler satellite surveying techniques. It was used as the
reference frame for broadcast GPS Ephemerides (orbits) beginning January
23, 1987. At 0000 GMT January 2, 1994, WGS 84 was upgraded in accuracy
using GPS measurements. The formal name then became WGS 84 (G730) since
the upgrade date coincided with the start of GPS Week 730. It became the
reference frame for broadcast orbits on June 28, 1994. At 0000 GMT
September 30, 1996 (the start of GPS Week 873), WGS 84 was redefined
again and was more closely aligned with International Earth Rotation
Service (IERS) Terrestrial Reference Frame (ITRF) 94. It is now formally
called WGS 84 (G873). WGS 84 (G873) was adopted as the reference frame
for broadcast orbits on January 29, 1997. 

5. You might also want to check out how geo lat-long are being expressed
(proposal) as part of OpenSearch and GeoJSON.
http://www.opensearch.org/Specifications/OpenSearch/Extensions/Geo/1.0/D
raft_1 . I have concerns that multiple methods of expression are
emerging. A killer for interoperability.

Regards

Carl Reed

----- Original Message ----- 

To: "Alexander Mayrhofer" <[email-masked]>; "GEOPRIV"
<[email-masked]>

Subject: Re: [Geopriv] Fw: New Version
Notificationfordraft-mayrhofer-geopriv-geo-uri-00

---

From: "Alexander Mayrhofer" <[email-masked]>
Date: Wed, 28 May 2008 10:39:26 +0200

Carl, thanks for the review and the suggestions. 

comments inline.

> 1. You need to be much more specific about the use of WGS 84. 
> In order to be as clear as possible, I would suggest using 
> the following words:
> 
> Geographic locations in this document are defined using WGS 
> 84 (World Geodetic System 1984), equivalent to the OGP 
> Surveying & Positioning Committee EPSG code 4326 (2 
> dimensions). This document does not assign responsibilities 
> for coordinate transformations from and to other Spatial 
> Reference Systems. A WGS-84 coordinate value is here 
> represented as a comma-delimited latitude/longitude pair, 
> measured in decimal degrees (un-projected). Latitudes range 
> from -90 to 90 and longitudes range from -180 to 180. 
> Coordinates in the Southern and Western hemispheres are 
> signed negative with a leading dash. http://www.epsg.org/ 
> 
> There is also now an on-line registry of the EPSG database so 
> the exact parameters for the WGS-84 - 2d datum can be referenced. 

I guess we'll add most that text to the next revision, and your name to
the acknowledgement section :)

> 2. I think "altitude" needs to be a bit more clerly and 
> consistently defined. In one place the document mentions 
> "mean sea level" and in another "earth's surface".

point taken, will improve for the next revision
 
> http://tools.ietf.org/html/draft-daviel-http-geo-header-05 . 
> Similar but different approach to the same problem. For 
> example, the authors of this document do address to a certain 
> extent civic addresses as well as uncertaintly. This document 
> is targeted a bit more at the geo-enabled mobile community.

I know that document, i did talk to Andrew on the IETF back in Vancouver
about this. It tackles a similar problem space, but is limited to a
certain protocol. I think i remember he was asked to move more towards
the PIDF-LO (CAtype) formats during the last Geopriv session..

> 4. Back to WGS. Might want to mention that WGS stands for 
> World Geodetic System. Also, WGS-84 predates GPS but GPS was 
> used to upgrade WGS-84.

thanks - i guess you noticed i'm not a geodetic pro :)

> From US National Geodetic Survey: WGS 84 is the World 
> Geodetic System of 1984. It is the reference frame used by 
> the U.S. Department of Defense (DoD) and is defined by the 
> National Geospatial-Intelligence Agency(NGA 
> <http://www.nga.mil/> ) (formerly the National Imagery and 
> Mapping Agency) (formerly the Defense Mapping Agency). WGS 84 
> is used by DoD for all its mapping, charting, surveying, and 
> navigation needs, including its GPS "broadcast" and "precise" 
> orbits. WGS 84 was defined in January 1987 using Doppler 
> satellite surveying techniques. It was used as the reference 
> frame for broadcast GPS Ephemerides (orbits) beginning 
> January 23, 1987. At 0000 GMT January 2, 1994, WGS 84 was 
> upgraded in accuracy using GPS measurements. The formal name 
> then became WGS 84 (G730) since the upgrade date coincided 
> with the start of GPS Week 730. It became the reference frame 
> for broadcast orbits on June 28, 1994. At 0000 GMT September 
> 30, 1996 (the start of GPS Week 873), WGS 84 was redefined 
> again and was more closely aligned with International Earth 
> Rotation Service (IERS) Terrestrial Reference Frame (ITRF) 
> 94. It is now formally called WGS 84 (G873). WGS 84 (G873) 
> was adopted as the reference frame for broadcast orbits on 
> January 29, 1997. 
> 
> 5. You might also want to check out how geo lat-long are 
> being expressed (proposal) as part of OpenSearch and GeoJSON. 
> http://www.opensearch.org/Specifications/OpenSearch/Extensions
> /Geo/1.0/Draft_1 . I have concerns that multiple methods of 
> expression are emerging. A killer for interoperability.

I definitely agree - however, all formats that use simple lat/lon in
WGS84 can nicely interoperate. And, the primary goal for the URI is to
refer to something of the user's choice - a browser with "geo:" support
could offer a search on OpenSearches that are geo-enabled, for example
(like operator offers various ways to use a location today).

thanks for the comments!

Alex