Jon

The full or double cubit measures mentioned by Petrie don't cut it with me. Dividing by 28 seems reasonable in anyone's language (not mine of course) but even so there are very few courses where we can apply units of the cubit with any definition, grouped or non grouped. The measures Petrie took on opposing sides of the pyramid are quite remarkable for their agreement and as we follow them up the pyramid, course by course, we get a pretty good picture of how they applied their technique. Individual courses cannot be matched to any standard cubit, common, royal, or otherwise, or divisions thereof for that matter, at least not to those cubits we are aware of for Khufu's monument. The courses laid gradually became more level as the masons gained experience and there is coinciding data for the diagonals of many courses which illustrate just how competent they eventually became at levelling once they overcame the rock base on which they built.

It is just another case of not being able to convert Petrie's imperial measures into any known cubit or division of same. On reflection, the only cubits of the monument that have definitely been identified are those applied to the chambers, king's in particular, and so we could probably say that the term "royal" was aptly named.

I agree with your concern, and Dave's, on imported measures.