SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Is there a reason that your valve placements would not be visible to the naked eye?

It might be more practical to simply copy the old technique for documenting buried water well locations, which was to take measurements to the two nearest corners of the house, making a triangle that will allow anyone with a tape measure to pinpoint a valve box.

Another practical no-high-tech-required idea is to use larger valve boxes. While I realize it is Texas custom to put each valve into its own tiny round box, as opposed to systems with large rectangular boxes holding half a dozen valves, it might serve you well to use a certain large round box, originally made by Ametek, to contain one or two zone valves. While there are many similar boxes, the Ametek design allowed the placement of a 3-inch extension piece on the existing box, for when turf buildup finally threatens to completely bury old boxes.

That is a bit of an overkill for most jobs. In 29 years of professional consulting experience, including large projects such as regional parks, parkways, etc. I have never seen it done. Some times there are some designers working for engineering firms that like to show off some skill that it is not common to others, and add it to the construction documents (plan).
The designer needs to keep the construction documents, including plans, simple and easy to read for everyone ... less is more.
Using some elements that are part of the hardscape as reference landmarks, and adding a dimension that is easy to read and understand works very well, and should not for a Land Surveyor to go out ad set the valve(s) location(s).