[UW-GIS-L] Best projection for measuring distances across theWestern Hemisphere?

[Michalis Avraam]

Phil,

The ST_Distance function can use both the Vincentry and Haversine formulae
(I believe since 1.5). There is an option use_spheroid one can use to get
this behavior, which doesn't seem to be mentioned in that OpenGeo page.

Michalis


On Thu, Oct 21, 2010 at 11:33 PM, Phil Hurvitz <phurvitz at uw.edu> wrote:


> Hi Tristan, you might consider PostGIS, which supposedly calculates great

> circle distances. This is a good synopsis:

>

> http://workshops.opengeo.org/postgis-intro/geography.html

>

> -P.

>

> **************************************************************

>    Phil Hurvitz, MFR | PhD Student, Urban Planning | CBE

>        1107 NE 45th Street, Suite 535 | Box 354802

> University of Washington, Seattle, Washington  98195-4802, USA

> phurvitz at u.washington.edu | http://gis.washington.edu/phurvitz

> "What is essential is invisible to the eye." -de Saint-Exupéry

> **************************************************************

>

>

> On 10/21/2010 10:55 PM, Jin-Kyu Jung wrote:

>

>> I think It should be one of equal-distance projections. In ArcGIS,

>> Azimuthal Equidistant, Equidistant Conic or Equidistant Cylindrical can be a

>> good option. I am a little bit surprised that ESRI help site suggested

>> conformal, equal area (e.g. sinusoidal) or even compromised Robinson

>> projection to measure an accurate distance, though. Please, someone correct

>> me if I am wrong. Thank you!

>>

>> Jin-Kyu Jung

>>

>> On Oct 21, 2010, at 10:30 PM, Keven Bennett wrote:

>>

>>  World Robinson is the best I know of.

>>>

>>> Keven

>>>

>>> -----Original Message-----

>>> From: uw-gis-l-bounces at mailman1.u.washington.edu

>>> [mailto:uw-gis-l-bounces at mailman1.u.washington.edu] On Behalf Of Tristan

>>> Nunez

>>> Sent: Thursday, October 21, 2010 8:58 PM

>>> To: uw-gis-l at u.washington.edu

>>> Subject: [UW-GIS-L] Best projection for measuring distances across

>>> theWestern Hemisphere?

>>>

>>> Hi GIS folks,

>>>

>>> Do you have any suggestions on the best projection to use to measure

>>> distances in km (using the Euclidean distance tool in Arc 9.3) ranging

>>> from 0 km to 1000 km, across the Western Hemisphere? The map is

>>> currently in GCS_WGS_1984.

>>>

>>> Sources on the web and in ESRI's help site suggest that the Bipolar

>>> Oblique Conformal Conic projection was useful for this purpose, but

>>> ArcMap 9.3 doesn't have it in its coordinate systems library. From the

>>> ArcMap 9.3 help files, it seems like a sinusoidal projection centered

>>> at 90 W, a Robinson projection, or doing North and South America

>>> separately in a Lambert Conformal Conic projection would be the best

>>> compromise.

>>>

>>> Any thoughts would be highly welcome.

>>>

>>> Many thanks,

>>>

>>> Tristan

>>>

>>> --

>>> Tristan Nuñez

>>> Master of Science Candidate

>>> Landscape Ecology and Conservation Lab

>>> University of Washington

>>> tristan.nunez at gmail.com

>>> c. 503-819-5884

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>>

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