Which device is often used to ensure accurate horizontal measurements?

A digital theodolite is a highly precise instrument used in surveying to measure both horizontal and vertical angles. It plays a crucial role in ensuring accurate horizontal measurements because of its advanced technology and features. The device typically includes digital readouts that minimize human error often associated with reading traditional instruments. Additionally, digital theodolites can integrate with other surveying equipment to enhance overall accuracy, streamline data collection, and allow for the easy transfer of measurements to computer software for analysis. This level of precision is essential in various surveying tasks, making the digital theodolite indispensable for professionals in the field.

While surveying compasses can provide useful angle measurements, they do not offer the same level of precision as digital theodolites. Smartphone apps can assist with measurements but generally rely on the device's sensor capabilities and may lack the accuracy needed for professional surveying tasks. A staff gauge is primarily used to measure the depth of water or similar applications, making it unsuitable for providing horizontal measurements.