During my first 7-8 years of Federal employment with the USDA Soil Conservation Service, I walked many miles carrying a "Philadelphia Rod" as shown in the picture. While this picture appears to have been taken just for showing the vegetation in the drainage area, we spent much of our time surveying gradient terraces. It required a 2-man crew (Yes, that was prior to women doing survey work). I usually carried the "Rod" and my helper would "read the David White Level". The "Level" was a telescope with a "cross hair" that enabled the "Instrument Man" to determine whether the "Rod Man" needed to more to higher or lower spots on the hillside. The sight of the "target" on the Rod would need to be exactly on the cross hair in the Level when the desired spot was found to put in a marking stake. The Rod Man would step off 50 feet and the process would be repeated. The Target on the Rod would be moved up 2 tenths of a foot each 50 feet to provide the gradient in the terrace. The Terrace would be constructed along the line of the stakes "laid out" by this process. And to think that many years later when I took up the game of golf, a Buddy told me that Golf wasn't as simple as Soil Conservation.