Graphics Gems by Andrew S. Glassner

Author:Andrew S. Glassner [Glassner, Andrew S.]
Language: eng
Format: epub, mobi, pdf
Tags: Computer Graphics Mathematics, Computer Graphics, Programming, Games, Computers
ISBN: 9780122861666
Google: fvA7zLEFWZgC
Amazon: 0122861663
Publisher: Academic Press
Published: 1993-07-13T00:00:00+00:00

V.6 ALBERS EQUAL-AREA CONIC MAP PROJECTION

Figure 2. Continental United States projection. Dashed lines show standard parallels

and cross marks the center of the projection.

USGS Standard Parallels

Region

North Parallel

South Parallel

Continental USA

45.5

29.5

North America

60.0

20.0

Alaska

65.0

55.0

Hawaii & Phillipines

18.0

8.0

Implementation

Implementing map projections is similar to implementing hash tables.

One usually consults a reference, finds the appropriate algorithm, and

translates the reference pseudo-code into the language of choice. De-

tailed understanding is often not required. Detailed description of the

formulae presented here is not given. Those interested might derive the

simpler spherical Albers projection and certainly should obtain USGS,

from which most of the notation and math was taken.

GRAPHICS GEMS I Edited by ANDREW S. GLASSNER

323

V.6 ALBERS EQUAL-AREA CONIC MAP PROJECTION

Two functions are used repeatedly in the calculations. The first, de-

noted by q ← F(lat), is given a latitude and produces q:





 

q ←(1− e 2)

sin( lat)





− 1 ln 1− e sin( lat)



 ,

1− e 2sin2( lat)

2 e

 1+ e sin( lat) 

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