We propose a robust geometry-constrained scale estimation approach for monocular visual odometry, which takes the camera height as an absolute reference. Visual odometry is an essential module for robot self-localization and autonomous navigation in unexplored environments. Scale recovery is an indispensable requirement for monocular visual odometry, since it compensates for the metric information lost by a single camera and helps to reduce the scale drift. When the camera height is considered the absolute reference, the precision of scale recovery depends on the accuracy of the road point selection and road geometric model calculation. However, most of the previous approaches solve these two problems sequentially, and their road point selection is based on the color model of the road or prior-knowledge-based fixed region. In this paper, we propose combining and iteratively solving these two problems. We adopt the geometric model, instead of the color model, of the road to select the road points. Furthermore, the selected road feature points are used to estimate the road model, which limits the road point selection. In detail, we segment our feature points with Delaunay triangulation and select road points based on the depth consistency and road model consistency. The experiments on the KITTI dataset show that our method achieves the best performance among state-of-the-art monocular visual odometry methods.

Blockchain technology has developed rapidly and has been applied in various areas. Blockchain technology has the features of decentralization, transparency, autonomy and tamper resistance etc. The blockchain, with its unique features, can address some problems in traditional areas. In traditional games area, especially the gambling game, we learn that there is a strong requirement for fairness and random numbers. But traditional games are centralized and cannot meet this requirement. Hence, we propose a blockchain-based random number generation algorithm that can provide a “true random number”. This algorithm allows all the participants to take part in the generation of a random number, which ensures that the random number will not be manipulated by anyone. We as well design a blockchain game platform adopting this random number generation algorithm. Traditional games can be deployed on this platform with a simple adaptation. Finally, we deploy a poker game on the platform to verify the algorithm and performance. The experimental results show that the algorithm is effective and the platform has good performance.

Scale recovery is one of the essential problems for monocular visual odometry. The camera height is usually used as an absolute reference to recover the scale. In this case, the precision of scale recovery depends on the accuracy of the road region detection and road geometrical model calculation. In previous works, road detection and road geometrical model calculation are solved sequentially: the road geometrical model calculation is based on the road detection and the road region detection is based on the color information. However, the color information of a road is not stable enough. In the proposed method, the estimated road geometrical model is taken into consideration to detect the road region as a feedback. Therefore, the road region detection and road geometrical model estimation can benefit each other. Delaunay Triangulation method is used to segment an input image to many triangles with the matched feature points as vertices. Every triangle region is classified as a road region or not by comparing their geometrical model with that of the road and the road geometrical model is updated online. We evaluate our visual odometry scale recovery method on the KITTI dataset and the results show that our method is achieving the best performance among all existing monocular visual odometry scale recovery methods without additional sensors.

Blockchain is the basic technology of bitcoin. With the value appreciation and stable operation of bitcoin, blockchain is attracting more and more attention in many areas. Blockchain has the characteristics of decentralization, stability, security, and non-modifiability. It has the potential to change the network architecture. The consensus algorithm plays a crucial role in maintaining the safety and efficiency of blockchain. Using a right algorithm may bring a significant increase to the performance of blockchain application. In this paper, we reviewed the basic principles and characteristics of the consensus algorithms and analyzed the performance and application scenarios of different consensus mechanisms. We also gave a technical guidance of selecting a suitable consensus algorithm and summarized the limitations and future development of blockchain technology.