China
Africa
Explore chapters and articles related to this topic
Geodesy
Published in Basudeb Bhatta, Global Navigation Satellite Systems, 2021
The earth is divided into various sectors by the lines of latitudes and longitudes. This network is called a graticule. A map projection denotes the preparation of the graticule on a flat surface. Theoretically, map projection might be defined as ‘a systematic drawing of parallels of latitude and meridians of longitude on a plane surface for the whole earth or a part of it on a certain scale so that any point on the earth surface may correspond to that on the drawing’. Whether we treat the earth as a sphere or a spheroid, we must transform its 3D surface to create a flat map sheet. This mathematical transformation is commonly referred to as a map projection (Yang et al. 2000; Bugayevskiy and Snyder 1995).
An Improved multivariate generalised likelihood ratio control chart for the monitoring of point clouds from 3D laser scanners
Published in International Journal of Production Research, 2019
Sue E. Stankus, Krystel K. Castillo-Villar
This research presents a new methodology that captures the true 3D nature of data from scanned objects in a MGLR control chart. The theoretical contributions include (1) the mathematical expansion of formulas from two dimensions to three dimensions and (2) the application of a Fourier transform to the point errors to expose defects. With this new methodology, the point cloud from a scanned object can be used in its 3D form; the point cloud does not need to be unfolded or projected on to a 2D surface. A projection of a complex surface can lose valuable information regarding point density and proximity similar to the way regions near the earth’s poles are distorted on a flat map of the earth. In addition to retaining the 3D form, a Fourier transform was applied to the point errors to highlight defects in frequency space. When comparing the Fourier transform of a nominal part to the Fourier transform of a defective part, defects are emphasised more than when comparing the original point errors.
Mapping China’s offshore mariculture based on dense time-series optical and radar data
Published in International Journal of Digital Earth, 2022
Xiaoliang Liu, Zhihua Wang, Xiaomei Yang, Yueming Liu, Bin Liu, Junyao Zhang, Ku Gao, Dan Meng, Yaxin Ding
The tidal flat map of China (China_Tidal Flat, CTF) was used to mask tidal flat areas in the post-processing procedure. (Jia et al. 2021). Tidal flats are transition zones between marine and terrestrial environments, including intertidal mudflats, rocks, and sands. Due to the proximity of mariculture to tidal flats in some coastal zones, they can easily be misclassified (Wang et al. 2019). The CTF map is the first 10 m spatial resolution tidal flat map covering the entire coastline of China. It is produced based on time series of Sentinel-2 images acquired in 2019 and 2020 with an overall accuracy of 95%.
SegVisRL: development of a robot's neural visuomotor and planning system for lunar exploration
Published in Advanced Robotics, 2021
Tamir Blum, Gabin Paillet, Watcharawut Masawat, Kazuya Yoshida
Figure 10 shows two cases highlighting some of the current limitations of the DRL controller observed during the 200 trials. Trial 3 shows a case where the DRL controller crashes into an obstacle on the flat map. This occurred 8% of the time on the flat terrain and 8.5% of the time on the bumpy terrain. Trial 2 shows a case where the DRL controller falls off the 25 m × 25 m map on the bumpy terrain. This occurred 6.5% of the time for the flat map and 5% of the time on the bumpy map. While the overall performance of the DRL agent was good, these cases showcase some room for improvement.