# Dictionary:Derivative map

A map of one of the derivatives of a field of values such as gravity, magnetics, time structure, etc. The objective of a derivative map is to emphasize short wavelength (high-frequency) anomalies.

**1**. Dip and azimuth maps generally involve the first horizontal derivative.

**2**. With potential fields the second vertical derivative [based on Laplace's equation, ] was once used widely, but it has largely been replaced by the total gradient or total horizontal derivative. The horizontal derivatives, and , are usually estimated by finite-difference methods from values measured at gridded points on a map, often using a residualizing template based on polar representation of the Laplacian or by 2D convolution with such a template. See Cordell and Grauch (1985).