Looks like Tim and Jay will run with water levels and that's very fine. My choice of old school optics relates to the environment I worked in during the 70's and 80's as crew leader and site manager. Among the projects I managed was a sprawling meandering house with 49 exterior corners. I was the guy who laid out the cut, the footings and foundation, so I was in need of serious optics to place the house. The surveyors transit and dumpy level were bought used for less than $500 total. To this day, such instruments can be found for similar prices. No electronics to go glitchy. All the details of operation and adjustment can be found in old surveying and engineering texts. The really cool aspect of old transits is the principle of recursion or the procedure of increasing resolution through repeated and accumulated readings.

Nineteenth century precise mechanical tech (although my gear is post WWII) will outlast any electronic device.