Image data and ground truth for evaluation of visual odometry algorithms primarily intended for tree nursery inspection machines

Dataset contains 112 RGB images taken using perpendicularly downward facing camera Alvium G5-508 with TECHSPEC® HR Series 16 mm Fixed Focal Length lens, sensor pixel size is 3.45 μm. Image resolution is 2432x2018, images are archived as ZIP file in "Images.zip" containing files "pxxx.png", where xxx is image id. Camera was calibrated using OpenCV tools (https://docs.opencv.org/4.x/dc/dbb/tutorial_py_calibration.html), and all images are undistorted using intrinsic matrix obtained as a result of camera calibration. In images Pinus sylvestris (the Scots pine, Scotch pine, Baltic pine, or European red pine) seedlings in cartridges with 40x40 mm cells are captured. For measuring purposes, a ruler is also captured in all images. Exact distance from camera to surface (cartridge with seedlings) was not measured, however it was not changing more than +/-1 mm during capture process. Images were captured with the camera being still with exposure and shutter speed set on auto. Each image was captured after camera was moved (translated) by 10 +/-1 mm over X axis, however due to camera driving mechanism construction, minor translation also over Y axis. Rotation movement was avoided. Camera was moved using rails with stepper motors. View of the experimental setup and axis description is given in file "Setup.pdf". File "Translations.txt" gives "ground truth" information: translation amount in pixels for both axes between consecutive frames. This was determined manually for all frames. Dataset is intended for evaluation of visual odometry algorithms primarily for tree nurseries.

本数据集包含112张RGB图像，均由Alvium G5-508垂直向下拍摄相机搭配TECHSPEC® HR系列16mm定焦镜头拍摄，传感器像素尺寸为3.45μm。图像分辨率为2432×2018，所有图像打包为ZIP压缩包"Images.zip"，其中图像文件命名格式为"pxxx.png"，xxx为图像编号。该相机已通过OpenCV工具（https://docs.opencv.org/4.x/dc/dbb/tutorial_py_calibration.html）完成校准，所有图像均使用相机校准得到的内参矩阵完成畸变校正。图像中拍摄了装载于40mm×40mm方格育苗盘的欧洲赤松（Pinus sylvestris，又称苏格兰松、波罗的海松或欧洲红松）幼苗，为便于尺寸测量，所有图像中均同步拍摄了标尺。相机到育苗盘表面的精确距离未进行测量，但拍摄过程中该距离的波动幅度不超过±1mm。拍摄时相机处于固定状态，曝光与快门速度设置为自动模式。每拍摄完成一张图像后，相机沿X轴平移10±1mm；受相机驱动机构结构限制，拍摄过程中Y轴也存在微小平移，全程未产生旋转运动。相机通过搭载步进电机的导轨完成移动。实验装置的视图与坐标轴说明见文件"Setup.pdf"。文件"Translations.txt"提供了"真值（ground truth）"信息，即相邻帧之间两个坐标轴方向上的像素平移量，该信息通过对所有帧手动标注得到。本数据集主要用于评估苗圃场景下的视觉里程计算法。