Simplify calculations by taking advantage of trigonometric functions. Often, triangle-based geometry will use some combination of sine (sin), cosine (cos) and tangent (tan) operations to deduce unknown variables. For instance, a surveyor 300 meters away from a vertical feature needs to position a sighting instrument 10 degrees above the horizontal plane to pinpoint the top of the feature.
Here, the tangent (tan) function comes in handy. Assume that the feature is at right angles to the horizontal. By definition, tangent(angle) = vertical/horizontal. In this case,
tangent(10 degrees) = vertical/300. Therefore, 300*tan(10 degrees) = vertical, or 52.898 meters above the level of the measuring instrument.
Combine natural and human factors to make predictions about the environment. Make recommendations accordingly. For instance, say a lake's water level rises or falls according to an equation that relates average annual temperature and water level. Land surveyors would use that equation to predict the water level in the near future.
Limit algebraic extrapolations. Equations and formulas usually do not capture the "feedback" and cyclical nature of natural phenomena -- or, if they do, they become exceedingly complicated. This is especially true with water-related surveying, as water levels are more responsive to temperature, pollution and other external conditions. Acid rain may alter lake chemistry. The modified lake water may erode subsurface features, carving out bigger niches for water to flow into, thereby reducing the rate of water level rise. Limitations on data, equipment, time, and expertise all serve to introduce unavoidable error into predictions about the future, no matter how skilled the surveyor.