Usually. To the trained eye, a casual look can sometimes be enough to yield a high probability for stability and determine the drilling/driving technique. However, for most locations, a thorough assessment of the topography, soil, slope stability, artificial fill, proximity to water wells and other factors are best done by an experienced geologist. The minor cost of this step is cheap insurance against an unreliable position timeseries. Take a look at the geologic stability section for impacts of data from unsuitable geologic conditions.