The ground reflection model, or the plane earth model [18, 19], is an a priori model.

Figure 8 shows the measurements of type A aisle, for Friis free space and plane earth models without correction factors.

It is observed, however, that the signal strength decay does not follow the plane earth model.

This fact is evidenced mainly by the RMSE value for free space that is lower than the plane earth model.

Regarding the plane earth model, the RMSE decreases, indicating a better fit, but the decay is not proportional to the fourth power of the distance.

Thus, the plane earth model is used, considering the heights of the nodes equal to 1 m, instead of 3 m (3 m for the total height from the ground, minus 2 m height of the piles).

For measurements taken up to a 100 meters, the gap relative to the top structure is approximately 0.6.R; that is, the plane earth and free space model leads to the same attenuation value.

Caption: Figure 8: Received power (dBm) as a function of distance, and Friis free space and plane earth models for type A aisle (linear scale for distance).

This packing is a mirror reflection and 90-degree rotation of one of the three 7x12 planet packings shown in my article "

Plane Earth Planet Packings" in the February 2005 Word Ways, with the position of the sun slightly shifted."

The Plane Earth Study and Teaching Society wishes to thank Word Ways' editor for generously granting us this opportunity to respond to his gravely misleading article in the May 2004 Word Ways entitled "Planet Packing in Two Dimensions." But before addressing that issue, we would like to acquaint the reader with our Society's basic tenets.

Briefly, Plane Earth believes that the universe is composed of a vast, mostly flat plane of infinite extent--the Earthplane--and the sky above it, and that what we think of as "the earth" is merely a locality on that plane.

In sum, Plane Earth's positionally proper planet packings are entertaining, educational, elegant and eminently estimable.