-------- Original Message --------
Subject: Re:      Re: world map projection for web]
Date: Tue, 29 Mar 2005 17:45:24 -0500
From: Paul B. Anderson <[log in to unmask]>
To: Maps and Air Photo Systems Forum <[log in to unmask]>
References: <[log in to unmask]>

------------------
- Hi All,

Dr. Carter of Illinois State University (Normal, IL) very eloquently
responded to an earlier version of this post. Jon, you still have not given
any purpose for your map so here are some general pointers:

If what you want to display a country or region on or near the Equator, use
a Cylindrical. If you want to display a country or region in the temporate
zones use a Conic. If you wish to display a country or region near the poles
use an Azimuthal.

If you want to display a country or region with minimal distortion for the
map projection you chose, change the map's ASPECT so that the area of
interest is positioned at the center of the map.

If you wish to construct a world statistical map, choose an Equal-area
Pseudocylindrical.

If you want to produce a world map that others can lift right off the web
page and use in a gis program choose the Plate Carrée (a couple of other
names of it are the equirectangular and unprojected).

While most schools teach 4 basic properties of a map projection, here is a
comprehensive listing of properties to ponder preserving when constructing a
map.

=============================
       Graticule Groups
  (or Fundamental Properties)
=============================
Azimuthal (or Planar)
* Perspective
* Non-perspective

Orthoapsidal
Pseudoazimuthal
Retroazimuthal

Conic
Polyconic
Pseudoconic

Cylindrical
Polycylindrical
Pseudocylindrical

Composit
Projections that are composed of two or more different map projections.

=======================
  Representation Groups
(or Special Properties)
=======================
1) Conformal

2) Equal-area (also Equivalent, or Authalic)

3) Neither Conformal nor Equal-area (also Arbitrary, or Aphylactic)
Consists of any of the following:

3a) Equidistant projections

3b) Approximately Equidistant projections
The Meridional particular scale is a constant value but it's not equal to
the principal scale

3c) Abstandsgleich (German term, no English Equivalent)
Has Equidistantly spaced parallels and variable meridional particular
scales.

3d) Abweitungstreu (German term, no English Equivalent)
The particular scale along the parallels is equal to the principle scale.

3e) Absolute Minimum Error projections
Sums of the squares of the errors in the particular scales, integrated
throughout the area mapped, have a minimum value.

3f) Minimum Error projections
Has one or more of the Special Properties but satisfies the secondary
condition that the sum of the squares of the errors in the particular
scale have a minimum value.

3g) Périgonale (French -- No English Equivalent)
The maximum values of Angular Deformation are reduced to a minimum value.

3h) Périhalique (French term -- No English Equivalent)
The maximum values of Area Distortion are reduced to a minimum value.

3i) Périmecoïque (French term -- No English Equivalent)
The maximum values of Linear Distortion are reduced to a minimum value.

3j) Projections that are 'Total Area True' (flächengleich or atractozonique)
and also satisfy some property other than equivalence.

3h) Orthodromic
Projections on which great circle arcs are rectilinear.

3i) Loxodromic
Projections on which rhumb lines are rectilinear.

========
  Aspect
========
Normal (or Direct)

First Transverse

Second Transverse

Simple Oblique

Transverse-Oblique

Skew

Plagal

============
  References
============
Wray, Thomas, 1974, The Seven Aspects of a General Map Projection,
Cartographica Monograph No. 11

Maling, D. H., 1968, The Terminology of Map Projections: International
Yearbook of Cartography, v. 8, p. 11-65

Lee, L. P., Jan 1944, The Nomenclature and Classification of Map
projections,
Empire Survey Review No. 51, Vol. VII, P. 190-200

============
Paul B. Anderson FCCS (USN, Retired)
Kingsport, TN native living in Norfolk, VA

My Map Projection Graphics:
http://www.ilstu.edu/microcam/map_projections/index.html



----- Original Message -----
From: "Johnnie D. Sutherland" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, March 29, 2005 16:19
Subject: Re: world map projection for web]


> -------- Original Message --------
> Subject:        RE: world map projection for web
> Date:   Tue, 29 Mar 2005 09:44:26 +1000
> From:   <[log in to unmask]>
> To:     <[log in to unmask]>
>
>
>
>
>
> Dear Listers
>
>
>
> Apologies in advance if this is déjà vu - I've had problems receiving
> list messages recently.
>
>
>
> Can anyone suggest a good projection for whole world web maps? It
> appears from observation that there are lots of Mercators used but the
> areal distortion is enormous so we would prefer a compromise between
> areal and shape accuracy. I suspect that "rectangular" projections (ie
> those which have straight lat and long lines) are perhaps easier for the
> public to use, but I have no inkling as to the veracity of this
> assumption. The projection must display Antarctica.
>
>
>
> Are Miller cylindrical, Winkel Tripel or Robinson projections popular
> for web mapping applications?
>
> Thanks
>
> Jon  Stirzaker
>   Geoscience Australia
>   E-mail:   [log in to unmask] <mailto:[log in to unmask]>
>