Re: [ubl-lcsc] [roe] OAG comment: LocationCoordinates

[Alan.Stitzer@marsh.com]

If we are going to do something like this, someone who knows more about GPS
"stuff" should be queried about input to this.

The insurance industry has Lattitude and Longitude as part of an Address,
but someone has stated that just those two coordinates could not put you
exactly where you think you are!

I have included an exceprt from some of the ACORD discussions on this
point:

>Does ACORD specify the geodetic datum that is to be used for the coordinate
>system (e.g., NAD27, NAD83, WGS84)? Please correct me if I am wrong, but as
I> understand it applying the same coordinate values (e.g., in a geocoding
>scenario) using different datums may result in significant error of
>potentially hundreds of meters. If this is correct then I would think that
>ACORD should either standardize the use of a particular datum or (better)
>add an element to the schema to contain the datum used.

NEW MESSAGE:

>With regard to datum...

>Simply put, the Earth is roughly ellipsoidal in shape and your "every-day"
map is flat. A projection is required to translate the coordinates of a
point on a round >surface to coordinates on a flat surface. Note that I
said "roughly ellipsoidal". Since we don't really know the exact shape of
the earth we must construct a model to >work with, a reference ellipsoid.
This model is what is used for the projection. Here's the catch. Many
different models exist, each shaped slightly differently. >Different models
will result in different coordinates.
>
>A datum is a point that acts as a control for coordinate calculations and
is associated with a reference ellipsoid. North American Datum 1927, North
American >Datum 1983, and World Geodetic Survey 1984 are some commonly used
datums ("data" is not the plural in this context). Trying to match NAD27
coords with >WGS84 coords, without an appropriate conversion algorithm,
will result in error.

NEW MESSAGE

>I'd have to check with our underwriters to see if they have a concern, but
this is the first time I've heard of this issue.   If using different datum
can produce errors of >hundreds of meters, as you say, one would think this
is significant when considering coast lines or slopes.




____________________
Alan Stitzer
AVP
Marsh USA Inc.
1133 Avenue of the Americas
New York, NY 10036-2774
Phone: (561) 743-1938
Fax: (561) 743-1993
Internet: Alan.Stitzer@marsh.com
____________________


<<< Memo from tmcgrath@portcomm.com.au@Internet on 03 July, 2003, 10:59:20
PM Thursday >>>


tmcgrath@portcomm.com.au@Internet on 3 Jul 2003, 22:59 Thursday

To:    ubl-LCSC
cc:      (bcc: Alan Stitzer)
Subject:    [ubl-lcsc] [roe] OAG comment: LocationCoordinates


To facilitate debate and consensus on the reviewed items, I am posting
relevant issues as discussion points.  The intention is that after a one
week period the team shall resolve these issues.  For example, this
issue will be resolved at the call on Friday July 11th.

Item 9.

The OAGIS Coordinate aggregate is contained within the Location
aggregate completely independent of the Address aggregate .  OAGIS has
also implemented a xsd choice group to separate GPS (latitude,
longtitude, altitude) from other map or grid coordinate systems.

Since GPS systems will most likely be the most common, it made sense to
provide structured aggregates for latitude and longtitude which included
degrees, minutes, seconds, and direction.

A generic structure was provided for non-GPS systems since these systems
may vary widely in their identification of coordinates.

Do we accept this modification?  How does the LocationCoordinate then
relate to the other ABIEs?

--
regards
tim mcgrath
phone: +618 93352228
postal: po box 1289   fremantle    western australia 6160



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