Unmanned aerial vehicles (UAVs) are modern tool for various scientific research areas such as agriculture, disaster management, mining and surveying. Among them, remote sensing is utilizing UAVs to acquire high-resolution digital images of ground surface. In remote sensing and photogrammetric operations, the geometric quality of the imagery basically depends on the relation between pixel size and the map scale, contrast information, atmosphere and the sun elevation, the printing technology, screen resolution and the visual acuity (ISPRS Int J Geo-Inf, Liu et al. Liu et al., ISPRS International Journal of Geo-Information 7:333, 2018; Eur Assoc Geosci Eng 1–5, Zatserkovnyi et al. Zatserkovnyi et al., European Association of Geoscientists and Engineers 25:1–5, 2020). In this study, accuracy has been assessed and compared of true digital orthoimages generated by two different software with same configuration. Three datasets of different places called dense urban, urban slum and forest mountains have been collected from field with area covering 0.061, 0.130 and 2.040 km² and ground sampling distance 1.79, 2.19 and 11.86 cm, respectively. The orthoimages were generated using Pix4D and AgiSoft Photoscan software and then randomly distributed checkpoints, and visual angular distortion on the orthoimage was used to verify its precision. It was observed that in dense urban and urban slum Pix4D accuracy is more than AgiSoft Photoscan, but in forest mountain, it is vice versa. However, the process and mapping accuracy to generate TDOI require further improvement.

无人机（UAV）是用于农业，灾害管理，采矿和勘测等各种科学研究领域的现代工具。其中，遥感技术正在利用无人机获取地面的高分辨率数字图像。在遥感和摄影测量操作中，图像的几何质量基本上取决于像素尺寸和地图比例，对比度信息，大气和太阳高度，打印技术，屏幕分辨率和视敏度之间的关系（ISPRS Int J Geo -Inf，Liu等.Liu等人，ISPRS国际地理信息杂志7：333，2018; Eur Assoc Geosci Eng 1-5，Zatserkovnyi等人Zatserkovnyi等人，欧洲地球科学家和工程师协会25： 2020年1月5日）。在这项研究中，已评估并比较了具有相同配置的两个不同软件生成的真实数字正射影像的准确性。从田间收集了三个不同地点的数据集，分别称为密集城市，城市贫民窟和森林山，面积分别为0.061、0.130和2.040 km²和地面采样距离分别为1.79、2.19和11.86厘米。正射影像是使用Pix4D和AgiSoft Photoscan软件生成的，然后是随机分布的检查点，并且正射影像上的视觉角度失真用于验证其精度。据观察，在人口稠密的城市和贫民窟中，Pix4D的准确性要高于AgiSoft Photoscan，但在森林山区则相反。但是，生成TDOI的过程和映射精度需要进一步改进。