In order to carry out a continuous and rational work in forest enterprises, it is important to determine the wood volume and increment amount of the trees periodically. It is necessary to measure the tree trunk diameter precisely in determining the wood volume of the trees for the different uses of the materials to be obtained from the trees. Tree trunk diameters are mostly measured manually with calipers. In this process, a forest worker measures the trunk diameter of the tree with a caliper, and another worker records this measurement information in the standing tree measurement report and then this information is transferred to the computer for further analysis. All these processes bring problems such as time, labor and measurement errors. In this study, it is planned to develop a low-cost portable measurement system consisting of a depth camera, single board computer and other peripherals with depth information in order to measure tree trunk diameters, and an experimental system was created to carry out preliminary tests. Some preliminary tests were carried out with the imaging system created in line with the target plan. In images containing depth information, the fact that a targeted tree trunk can be highlighted without being affected by the external lighting environment enables the tree trunk diameter to be determined precisely. 15 different measurements were performed, provided that the distance between the camera sensor and the tree trunk was within a certain limit value (20-100 cm), and tree trunk diameters were determined with a maximum error value of 1.975 cm according to manual caliper measurement.