Reducing noise levels in geodetic data is critical for the interpretation and modeling of geophysically interesting signals. In this paper, I estimate noise properties of continuous GPS time series collected on concrete pillar monuments and compare them with similar data from deep drilled braced monuments that are considered the most stable three-dimensional monuments available. I show that the time series noise properties are very similar between the monument types, at least for time series up to 4.5 years duration. Differences between the monument types are therefore not a dominant influence on these time series, implying that the less expensive concrete pillar monuments are a valid choice for recording many signals of geophysical interest.