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Gang Ai      
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Gang Ai published an article in August 2018.
Top co-authors
Xinqi Zheng

40 shared publications

School of Information Engineering, China University of Geosciences, Beijing 100083, China

Qing Huang

4 shared publications

School of Information Engineering, China University of Geosciences, Beijing 100083, China

Chunxiao Zhang

1 shared publications

Publication Record
Distribution of Articles published per year 
(2013 - 2018)
Total number of journals
published in
Article 0 Reads 2 Citations Generating a High-Precision True Digital Orthophoto Map Based on UAV Images Yu Liu, Xinqi Zheng, Gang Ai, Yi Zhang, Yuqiang Zuo Published: 21 August 2018
ISPRS International Journal of Geo-Information, doi: 10.3390/ijgi7090333
DOI See at publisher website ABS Show/hide abstract
Unmanned aerial vehicle (UAV) low-altitude remote sensing technology has recently been adopted in China. However, mapping accuracy and production processes of true digital orthophoto maps (TDOMs) generated by UAV images require further improvement. In this study, ground control points were distributed and images were collected using a multi-rotor UAV and professional camera, at a flight height of 160 m above the ground and a designed ground sample distance (GSD) of 0.016 m. A structure from motion (SfM), revised digital surface model (DSM) and multi-view image texture compensation workflow were outlined to generate a high-precision TDOM. We then used randomly distributed checkpoints on the TDOM to verify its precision. The horizontal accuracy of the generated TDOM was 0.0365 m, the vertical accuracy was 0.0323 m, and the GSD was 0.0166 m. Tilt and shadowed areas of the TDOM were eliminated so that buildings maintained vertical viewing angles. This workflow produced a TDOM accuracy within 0.05 m, and provided an effective method for identifying rural homesteads, as well as land planning and design.
Article 0 Reads 0 Citations Implementation of a Parallel GPU-Based Space-Time Kriging Framework Yueheng Zhang, Xinqi Zheng, Zhenhua Wang, Gang Ai, Qing Huan... Published: 17 May 2018
ISPRS International Journal of Geo-Information, doi: 10.3390/ijgi7050193
DOI See at publisher website ABS Show/hide abstract
In the study of spatiotemporal geographical phenomena, the space–time interpolation method is widely applied, and the demands for computing speed and accuracy are increasing. For nonprofessional modelers, utilizing the space–time interpolation method quickly is a challenge. To solve this problem, the classical ordinary kriging algorithm was selected and expanded to a spatiotemporal kriging algorithm. Using the OpenCL framework to integrate central processing unit (CPU) and graphic processing unit (GPU) computing resources, a parallel spatiotemporal kriging algorithm was implemented, and three experiments were conducted in this work to verify the results. The results indicated the following: (1) when the size of the prediction point dataset is consistent, the performance of the method is robust with the increasing size of the observation point dataset; (2) the acceleration effect of the parallel method increases with an increased number of predicted points. Compared with the original sequential program, the implementation of the improved parallel framework showed a 3.23 speedup, which obviously shortens the interpolation time; (3) when cross-validating the temperature data in the Beijing Tianjin Hebei region, the space–time acceleration model provides a better fit than traditional pure space interpolation.
Article 0 Reads 0 Citations Design of a Model Base Framework for Model Environment Construction in a Virtual Geographic Environment (VGE) Chunxiao Zhang, Gang Ai, Xinqi Zheng, Kun Fang, Jiayang Li Published: 04 May 2017
ISPRS International Journal of Geo-Information, doi: 10.3390/ijgi6050145
DOI See at publisher website ABS Show/hide abstract
The model environment is a key component that enables a virtual geographic environment (VGE) to meet the scientific requirements for simulating dynamic phenomena and performing analyses. Considering the comprehensiveness of geographic processes and the requirements for the replication of model-based research, this paper proposes a model base framework for a model environment of a VGE that supports both model construction and modelling management, resulting in improved reproducibility. In this framework, model management includes model metadata, creation, deposition, encapsulation, integration, and adaptation; while modelling management focuses on invoking the model, model computation, and runtime control of the model. Based on this framework, to consider the problem of ever-worsening air quality, we applied the Linux-Apache-MySQL-Perl stack plus Supervisor to implement the model base to support a VGE prototype using professional meteorological and air quality models. Using this VGE prototype, we simulated a typical air pollution case for January 2010. The prototype not only illustrates how a VGE application can be built on the proposed model base, but also facilitates air quality simulations and emergency management.
Article 0 Reads 0 Citations Design of Light-Small Mobile 3D Laser Measurement System Yi Bo Sun, Xin Qi Zheng, Zong Ren Jia, Gang Ai Published: 01 September 2013
Applied Mechanics and Materials, doi: 10.4028/
DOI See at publisher website