Search

The hydrologic coding of a dendritic river system can be used to indicate the stream order and spatial-structure features of a river system. However, most conventional hydrologic coding systems use a top down (i.e., from the source to the estuary) approach, which does not accurately reflect the hierarchies of a dendritic river system. Based on Gravelius’ definition of stream order, we have proposed an automated bottom up (i.e., traced from the estuary to the source) coding system for dendritic river systems. Firstly, directed topology trees are constructed to organize the data of a river network, followed by the calculation of stroke connections to construct river entities and identify the main stem. Secondly, the river system is then progressively coded from the estuary up to the source according to the definition of stream order in our system. Finally, actual topographic map data of a river system in some regions of Hubei Province are used to comparatively validate our hydrologic coding system against Horton’s coding system. The experimental results demonstrate that our coding system is very effective in highlighting hierarchies formed by catchment relationships. Our method is also found to be suitable for the selection of streams in topologically shallow dendritic river systems with uniformly distributed tributaries.

Merging is an important operation for the generalization of land-cover data. However, current research often entails merging on a global perspective, which is not conducive to capturing the spatial characteristics of geographic objects with significant spatial structures, i.e., structured geographic objects. As such, this paper proposes an area merging method that can maintain the boundary characteristics of the structured geographic objects. First, we identify the structured geographic objects based on the description parameters of the spatial structure. Second, a Miter-type buffer transformation is introduced to extract the boundary of each structured geographic object, and area elements inside the boundary are processed with corresponding merging operations. Finally, the boundary of the structured geographic objects and the merging result of the area elements are inserted back into the aggregated result of the original land-cover data using the NOT operation. The proposed approach is experimentally validated using geographical condition census data for a city in southern China. The experimental validation indicates that the proposed approach not only reasonably identify the typical characteristics of structured geographic objects but also effectively maintains the boundary characteristics of these objects.

This article primarily describes the nature of geoinformatics, including the role of each of its components as understood today, and illustrates how the change in demand and the progress in science and technology are the two driving forces for the development of this subject. The changes in popular needs are next analyzed in detail, focusing on four aspects: the user group, intended usage, medium, and service. Lastly, it points out that geoinformatics work should be conducted following the development of geographic information.

Spatio-temporal big data cloud platform is an important spatial information infrastructure that can provide different period spatial information data services, various spatial analysis services and flexible API services. Activities of policy coordination, facilities connectivity and unimpeded trade on the Belt and Road Initiative (B&R) will create huge demands to the spatial information infrastructure. This paper focuses on researching a distributed spatio-temporal big data engine and an extendable cloud platform framework suits for the B&R and some key technologies to implement them. A distributed spatio-temporal big data engine based on Cassandra™ and an extendable 4-tier architecture cloud platform framework is put forward according to the spirit of parallel computing and cloud service. Four key technologies are discussed: 1) a storage and indexing method for distributed spatio-temporal big data, 2) an automatically collecting, processing, mapping and updating method of authoritative spatio-temporal data for web mapping service, 3) a schema of services aggregation based on nodes registering and services invoking based on view extension, 4) a distributed deployment and extension method of the cloud platform. We developed a distributed spatio-temporal big data centersoftware and founded the main node platform portal with MapWorld™ map services and some thematic information services inChina and built some local platform portals for those countries in the B&R area. The management and analysis services for spatio-temporal big data were built in flexible styles on this platform. Practices show that we provide a flexible and efficient solution tobuild the distributed spatio-temporal big data center and cloud platform, more node portals can be aggregated to the main portal bypublishing their own web services and registering them in the aggregation schema. The data center and platform can support thestorage and management of massive data well and has higher fault tolerance and better scalability.

With the globalization and rapid development every filed is taking an increasing interest in physical geography and human economics. There is a surging demand for small scale world map in large formats all over the world. Further study of automated mapping technology, especially the realization of small scale production on a large scale global map, is the key of the cartographic field need to solve. In light of this, this paper adopts the improved model (with the map and data separated) in the field of the mapmaking generalization, which can separate geographic data from mapping data from maps, mainly including cross-platform symbols and automatic map-making knowledge engine. With respect to the cross-platform symbol library, the symbol and the physical symbol in the geographic information are configured at all scale levels. With respect to automatic map-making knowledge engine consists 97 types, 1086 subtypes, 21845 basic algorithm and over 2500 relevant functional modules.In order to evaluate the accuracy and visual effect of our model towards topographic maps and thematic maps, we take the world map generalization in small scale as an example. After mapping generalization process, combining and simplifying the scattered islands make the map more explicit at 1 : 2.1 billion scale, and the map features more complete and accurate. Not only it enhance the map generalization of various scales significantly, but achieve the integration among map-makings of various scales, suggesting that this model provide a reference in cartographic generalization for various scales.

This paper was aimed at analyzing and verifying each of the parameter settings in the computing process of GAMIT. The optimum number of introduced auxiliary station was determined, and models for the weighted mean temperature of the atmosphere in Guilin were established. Under the underlying strategy of introducing all the respective most optimum criteria, the precipitable water vapor (PWV) was first calculated by using the data provided by the CORS base station in Guilin, before analyzing and comparing it with the PWV and actual precipitation obtained from the sounding data. According to the result, a high degree of coincidence was discovered among the general trend of the following three indicators: the calculated PWV, as well as the PWV and actual precipitation acquired using the sounding data, hence offering a significant value for reference in terms of extreme weather warning.

By calculating the zenith troposphere information from 11 reference stations of the CORS network in Guilin City, Guangxi Province in 2018 by GAMIT10.6 as the reference values, analyzing the relationship between the zenith troposphere and the elevation, as well as the latitude in the Guilin Region, building a model for the zenith tropospheric delay (ZTD) suitable for the Guilin Region, uniformly selecting 8 CORS reference stations in the Guilin Region to build a new model, comparing with the ZTD estimated by GAMIT10.6 and studying the applicability of the new model in the Guilin Region, the results showed that: 1) In the Guilin Region, the ZTD presented linear negative correlation with the station elevation; 2) the ZTD estimated by the new model was well consistent with the reference value, with high precision, and increased with the elevation.