The Geometer is a new device that enables the user to accurately measure bearing and inclination angles to any visible target. It is designed for use by observers on distance sampling surveys and replaces the forestry inclinometers commonly used on aerial surveys. The Geometer is designed for ease of use, to reduce observer error and to eliminate the need for time-consuming and error-prone data transcription. The Geometer has been used successfully in multiple countries for aerial cetacean survey since 2015, and a new improved version is presently being developed.