Marching camp construction

[MonsGraupius]

I am currently thinking on how its done.
as Roman  agrimensor and Proffesional surveyor it has my interest.
As fas as I know  the surveyor had 1/10 of the troops at his disposal and went in front of the main body of the legion.
He would get his info from scouts and the auxilary which would go even before him.
he had to make the decision where to camp by that info.

Although it's not been my main interest, given the topic is about setting out a camp, I started trying to work out what likely happened when troops arrived and therefore the priorities. I won't go into the detail but the key points are:

1. The first priority is to work out where the defences are going. If terrain permits, this is a simple rectangle, otherwise it's as close as they can get given the terrain, but we get all different kinds of shapes, but usually four sided. The defences need to be marked by reference points. I think the most likely point is at the inner limit of the defences because everything outside of this can get disturbed as the defences are being built. It also means that troops can "muster" along the inside of this line as they arrive. Here they are out of the way of people building/surveying the camp and in a position to protect the camp as they form of human shield and ready to start working on defences.
   
2. The next key point is the headquarters - which is where unit commanders go when they arrive (even if HQ just a bloke with a "clipboard"). On a four sided shape this could be located by the point where diagonals from the corners cross, or if there is a defined road through the location, it may have just been marked out to sit beside this "via principalis". This probably gets a very prominent marker and is quickly occupied by HQ staff even before there is any shelter for them.
   
3. The next component needed is the "via principalis" which marks one side of the various HQ buildings, praetorian, hospital, granaries, etc. It's also the principle road so locates the main gates.
   
4. The next priority is to mark the opposite side of the HQ which forms one side of another street, and then to mark out the area of each "barrack" (or tent equivalent) and then the streets between them
   

This rough grid quickly defines the defences, the intervallum space and principle streets, which in turn locate the four gates. This marks out the principle components of the camp and creates a basic set of "arteries" that need to be kept unclogged to allow troops and equipment to move through the camp.