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The Nile Decoded

by Goro Adachi

Copyright © 2003 Goro Adachi
All rights reserved.

Appendix 2

On Map Projections and Interaction

 

Working with maps without understanding their subtle mechanics can easily lead to inconsistency and confusion. The level of complexity involved is actually quite surprising. Although probably of minute significance to the average reader, those seeking to investigate the Time River system in depth are advised to know the following basic points. 


Orthographic Azimuthal Projection

Because there are countless ways to express a spherical globe on a two-dimensional plane, there are many types of map projections. People use different projections for different purposes.

For the Time River overlay scheme, we are forced to use a virtual globe computer program and nothing less. Conventional maps containing various spatial distortions are just not suited for the purpose of this operation – which is to see two or more different geographical regions in superimposition. We really need the digital flexibility and precision of a virtual globe to create large-scale geographical overlays.

And preferably the simulated Earth is an ‘orthographic azimuthal projection’. It shows a natural-looking globe, but its geometry is as viewed from infinitely far away. (See Figures A2.1 and A2.2.)


Figure A2.1  Orthographic Azimuthal Projection.



Figure A2.2  Comparison.

If the required operation is to just make a map overlay, it doesn’t really matter whether the virtual globe is an orthographic azimuthal projection or a truer representation of the earth (i.e. a perspective view from a fixed point in space), as long as the size, or distance, is consistent.

But if the operation requires you to combine a map with something else (such as a sky projection or a painting), the globe’s projection type becomes an important issue, because there would be varying results depending on the selection.

The orthographic azimuthal projection becomes a better choice in this case because it would eliminate one variable – the distance between the viewpoint and the earth – in determining the overlay configuration. This makes the whole process much simpler.


Aligning Maps

How to align multiple maps/globes in superimposition is another important and tricky issue for the Time Rivers. It turns out that comparing two areas of the planet separated by a great distance – especially in terms of latitude – is not as simple as it sounds.

First, it is imperative that the centers of all the projections used in an overlay composite would coincide when put in place so that the spatial distortions are uniform among the maps.


Figure A2.3  How to produce a large-scale map overlay. (The end product of this example is the ‘Eden Overlay Configuration discussed in the Nile Decoded paper.)

But this alone still does not ensure consistency. We also need to carefully decide where to place the centers of the projections before bringing them together, as this would actually produce varying results. (See Figure A2.4 for a demonstration of this.) This process can be rephrased as choosing the ‘central meridian’ or, as I like to say, ‘anchor meridian’.


Figure A2.4  The position of the anchor meridian (central meridian) affects the overlay configuration.

As made clear in the author’s book The Time Rivers, the prime ‘anchor meridian’ selected, or detected, for the Time River system is 33°E longitude.

All these points should be carefully taken into account when attempting to replicate, confirm, or criticize findings presented in the book or the Nile Decoded paper.

 

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Copyright © 2003 Goro Adachi
All rights reserved.


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