Knowledge of underground structures is essential in the construction industry. For example, deploying sensors in boreholes helps determine the depth at which sheet pile or foundations may be found. In common with UXO detection, Mag-13 three-axis sensors, and Grad-13 gradiometers can be used to detect changes in magnetic field associated with nearby structures. The same tools can be used to detect underground features such as pipes, well casings, and cables, so that they may be avoided. Our range includes sensors for integration into utility location tools. In offshore work, our sensor arrays based on the Mag-13 or Grad-13 can be used for mapping the location of cables.