Trend surface examples
Trend surfaces are widely used by geologists, particularly in petroleum exploration, as a means of separating a mapped variable into two components, the trend and the residuals from the trend. The trend corresponds to the concept of "regional features," while residuals represent "local features." Used in this manner, trend surface analysis is a global method for filtering spatial data.
This plot shows Bouguer gravity data for northwest Kansas. While there are several interesting features, there is also a strong west-to-east trend.
The first-order polynomial of the gravity data set shows the strong east-to-west gradient.
Once the background gradient is removed, the local anomalies are displayed more clearly.
more on trend surface analyses...