[Proj] Proj Digest, Vol 113, Issue 8

Fri Oct 25 11:48:55 PDT 2013

The original question in this "thread" was with respect to projection bounds, and specifically UTM:

"Is there a way to find out the bounds of a given projection?
Let’s say I have a given projection (UTM) and have a point (supposedly in the same utm) but I want to find out if that point is within the bounds of the projection."

 I see this has devolved to a discussion on the variation of datum shifts with respect to geographic areas.  The "new" topic needs to recognize datum shifts accomplished with MREs, NTv2, NadCon, 3-parameter rigid-body geocentric shifts and 7-parameter Molodensky and Bursa-Wolf shifts.

Each tool works within its intended design area, but DOES require some basic knowledge of geodesy for proper implementation.  If you're going to teach GIS, you need to first teach the basics of the geodetic foundation of the system.

Clifford J. Mugnier, c.p., c.m.s.

Chief of Geodesy

LSU Center for GeoInformatics (ERAD 266)

Dept. of Civil Engineering (P.F. Taylor 3531)

LOUISIANA STATE UNIVERSITY

Baton Rouge, LA  70803

Academic: (225) 578-8536

Research: (225) 578-4578

Cell:             (225) 328-8975

honorary lifetime member, lsps

fellow emeritus, asprs

member, apsg

________________________________
From: proj-bounces at lists.maptools.org [proj-bounces at lists.maptools.org] on behalf of Cusick, Joel [joel_cusick at nps.gov]
Sent: Friday, October 25, 2013 1:17 PM
To: proj at lists.maptools.org
Subject: Re: [Proj] Proj Digest, Vol 113, Issue 8

It is my experience that defined descriptive bounds tagged to coordinate systems has caused great confusion in GIS circles - especially for "legacy" systems.
NAD_1983_To_WGS_1984_2  for example, tagged for use in the Aleutians still is being used today with modern positional tools (like GPS).
Over the years, ESRI has refined their use of these and we welcome these changes.  See the red text on this page.
http://support.esri.com/cn/knowledgebase/techarticles/detail/24159

On Fri, Oct 25, 2013 at 9:00 AM, <proj-request at lists.maptools.org<mailto:proj-request at lists.maptools.org>> wrote:
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Today's Topics:

   1. Re: Projection bounds question (Hermann Peifer)

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Message: 1
Date: Thu, 24 Oct 2013 20:11:10 +0200
From: Hermann Peifer <peifer at gmx.eu<mailto:peifer at gmx.eu>>
Subject: Re: [Proj] Projection bounds question
To: "PROJ.4 and general Projections Discussions"
        <proj at lists.maptools.org<mailto:proj at lists.maptools.org>>
Message-ID: <526962BE.4090301 at gmx.eu<mailto:526962BE.4090301 at gmx.eu>>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 2013-10-24 17:57, Richard Greenwood wrote:
> Coordinate systems do not generally have defined bounds although there
> may be laws that govern where a given coordinate system is to be used.
> In theory, you could represent any place on the earth in any coordinate
> system.
>

(Ahem)

How would you represent a point at 52S 170W in ETRS89/LAEA Europe, also
known EPSG:3035? 52S 170W happens to be the antipodal point of the
coordinate system's projection centre.

Hermann

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End of Proj Digest, Vol 113, Issue 8
************************************

--
Joel Cusick
GIS Specialist
c: 907.280.9724 w: 907.644.3549
240 W. Fifth Ave. Anchorage AK 99501
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