The ideas of Alexander Thom appeared naturally from his work of measuring megalithic "monuments". In a very real sense he was reading them, albeit from the modern framework of a professional engineer versed in science and not as an archaeologist. Without Thom's work, there would have been scant discussion in 20th century Britain of these monuments as relating to astronomy. Now, in his absence, the archaeologists have fallen back to using far-from-proven anthropological speculations about megalithic superstitions about death and the afterlife, though perhaps tied to a rudimentary form of horizon astronomy.
The reasons archaeology in Britain successfully rejected Thom's ideas are the skill set archaeologists in Britain are trained, and then funded, to conduct. These skills are growing towards new technological means but, because of the dismissal of Thom's ideas, knowledge of astronomy, metrology or geometry are hardly applied when recording endangered or newly discovered monuments. This means that archaeologists are not trying to read the monuments as regards the "native" information they might contain, about megalithic astronomy, geometry and metrology, because extensive peer-reviewed papers exist which summarily dismantle theories involving these as almost completely wrong.
If someone does not go into a library to read its books, what are they there for? Thom found he could read megalithic monuments but now archaeologist's have convinced themselves that Thom has been scientifically refuted when he has not. This problem is uniquely fundamental to understanding the megalithic because the megalithic existed before the invention of writing. With no means to express their intellectual life except through their artifacts, these had to become like books and are "texts" in the sense of containing what was informing to their intellectual life.
It is therefore important to see that the triple and four square structures that define the key points in the Type A stone circle geometry would have formed a portable astronomical reference for any observatory designed to also measure sightlines to either horizon alignments or topographical features. Wherever such a design was reproduced, the invariant ratios between the lengths of the key types of year would be available. It is likely that a whole series of other geometries and demonstrations could be replicated within such a scheme, for measurement, reference and training.
In this sense then, the megalithic could reliably spread its cultural knowledge by providing a single standard reference length and a person versed in reconstructing the knowledge; to derive other units of length as required in building monumental designs, "in the field". A design incorporating multiple squares such as the Type A built upon a grid, could have been a standard observatory in megalithic Britain.