Strebe 1995 projection

Strebe first presented the projection at a joint meeting of the Canadian Cartographic Association and the North American Cartographic Information Society (NACIS) in August 1994.{{cite conference

| title = Why We Need Better World Maps, and Where to Start

| last = Strebe

| first = Daniel "daan"

| conference = Canadian Cartographic Association and North American Cartographic Information Society Joint Conference

| date = August 9–13, 1994

| location = Ottawa

}} Its final formulation was completed in 1995. The projection has been available in the map projection software Geocart since Geocart 1.2, released in October 1994.{{cite journal

| last = Strebe

| first = Daniel "daan"

| title = A bevy of area-preserving transforms for map projection designers

| year = 2018

| journal = Cartography and Geographic Information Science

| volume = 46

| issue = 3

| pages = 260–276

| doi = 10.1080/15230406.2018.1452632

| s2cid = 134864785

| url = https://www.researchgate.net/publication/324252646

}}

The projection is arrived at by a series of steps, each of which preserves areas. Because each step preserves areas, the entire process preserves areas. The steps use a technique invented by Strebe called "substitute deprojection" or "Strebe's transformation".{{cite journal

| first1 = Bojan

| last1 = Šavrič

| first2 = Bernhard

| last2 = Jenny

| first3 = Denis

| last3 = White

| first4 = Daniel "daan"

| last4 = Strebe

| title = User preferences for world map projections

| journal = Cartography and Geographic Information Systems

| year = 2015

| volume = 42

| issue = 5

| pages = 398–409

| doi = 10.1080/15230406.2015.1014425

| s2cid = 120691673

| url = https://www.researchgate.net/publication/273517879

}} First, the Eckert IV projection is computed. Then, pretending that the Eckert projection is actually a shrunken portion of the Mollweide projection, the Eckert is "deprojected" back onto the sphere using the inverse transformation of the Mollweide projection. This yields a full-sphere-to-partial-sphere map. Then this mapped sphere is projected back to the plane using the Hammer projection. While the projections named here are the ones that define the Strebe 1995 projection, the substitute deprojection principle is not constrained to particular projections.

The projection as described can be formulated as follows:

:$\backslash begin\{align\}$

x &= \frac {2D}{s} \cos \varphi_{\text{p}} \sin \lambda_{\text{p}} , \quad

y = s D \sin \varphi_{\text{p}} \\

s &= 1.35 \\

D &= \sqrt {\frac {2}{1 + \cos \varphi_{\text{p}} \cos \lambda_{\text{p}}}} \\

\sin \varphi_{\text{p}} &= \frac {2 \arcsin \frac{\sqrt{2} y_{\text{e}}}{2} + r y_{\text{e}}}{\pi} \\

\lambda_{\text{p}} &= \frac {\pi x_{\text{e}}}{4r} \\

r &= \sqrt {2 - y_{\text{e}}^2} \\

x_{\text{e}} &= s \frac {\lambda (1+\cos \theta)}{\sqrt {4\pi + \pi^2}} , \quad

y_{\text{e}} = 2 \frac {\sqrt \pi \sin \theta}{s \sqrt {4+\pi}},

\end{align}

where $\backslash theta$ is solved iteratively:

:$\backslash begin\{align\}$

\theta + \sin \theta \cos \theta + 2 \sin \theta &= \frac{1}{2} \left(4+\pi\right) \sin \varphi .

\end{align}

In these formulae, $\backslash lambda$ represents longitude and $\backslash varphi$ represents latitude.

Strebe's preferred arrangement is to set $s\; =\; 1.35$, as shown, and 11°E as the central meridian to avoid dividing eastern Siberia's Chukchi Peninsula. However, s can be modified to change the appearance without destroying the equal-area property.

• List of map projections

{{reflist}}

• [http://archive.nytimes.com/www.nytimes.com/slideshow/2011/11/07/science/20111107-tattoos-17.html?_r=2&pagewanted=all New York Times book review for Carl Zimmer's Science ink, showing the Strebe projection as a large tattoo.]
• [https://www.mapthematics.com/forums/viewtopic.php?f=8&t=223 First published formulation of the Strebe projection.]

{{Map projections}}

Category:Equal-area projections