Land Use Dataset of the Urban Fringe in Xi??an (2015)

Wang, B.¹  Huang, X. J.^1,2,3*  Wang, C.¹  Hu, K. L.¹

1. College of Urban and Environmental Sciences, Northwest University, Xi'an 710127, China;

2. Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, Xi'an 710127, China

3. Shaanxi Xi??an Urban Forest Ecosystem Research Station, Xi'an 710127, China

Abstract: The urban fringe is a transitional area between the urban built-up and rural areas. It is characterized by an interlaced state of land use and a fragmented landscape caused by the invasion of urban construction land into agricultural land. This data set contains Google Earth images that can be used to classify and interpret Landsat Thematic Mapper (TM) images of the Xi'an urban area and its adjacent areas in 2015 to obtain land use data. In combination with the spatial development trend of urbanization in Xi'an, we selected the proportions of construction land and farmland, and a landscape fragmentation index of each Jiedao in Xi'an to determine the boundary of the urban fringe, and obtained a land use data set of the urban fringe in Xi'an (2015). The results showed that the urban fringe of Xi'an includes 25 Jiedao, belonging to the Baqiao, Chang'an, Yanta, and Weiyang Districts and Fengdong New Town, and the land use types were mainly construction land, farmland, forest land, and other land uses. This data set is stored in .shp format and consists of 14 data files, with a data volume of 8.11 MB (compressed to one file, 4.78 MB). The research paper based on this data set was published in Volume 73, No. 6, of Acta Geographica Sinica (2018)

Keywords: urban fringe; land use; Xi??an; Jiedao

1 Introduction

In recent years, with China??s rapid urban expansion, the functional space of transportation, industry, and housing has spread to the suburbs of cities. However, the increase in the area of urban construction land has mainly occurred due to the assimilation of farmland into suburban areas, which has resulted in the urban fringe at the junction of urban and rural areas becoming severely and profoundly affected by urban spatial expansion^[1?C2]. Under this background, the urban fringe has been deeply affected by continuous spatial reconstruction and has frequently experienced a functional transformation. It has become the most unstable and sensitive area of many cities, and is also the region where urban?Csocial conflicts are particularly prominent. Because of its transitional, ambiguous, and dynamic characteristics ^[3], the boundary of the urban fringe is usually difficult to define accurately, which hinders the precise governance of cities. Therefore, it is of great significance to scientifically define the spatial scope of the urban fringe and grasp the dynamic changes of land use in the urban fringe to maintain a healthy and orderly urbanization.

As a significant consequence of urbanization, land use change is not only a typical feature of the urban fringe, but is also an important basis for defining the spatial scope of the urban fringe area. An interlaced state of land use and a fragmented landscape caused by the invasion of urban construction land into agricultural land are the main characteristics of the urban fringe ^[4]. This data set takes Xi'an as the research area, and classifies and interprets Landsat TM images of the Xi'an urban area and its adjacent areas in 2015 to obtain land use data. By combining this information with the spatial development trend of urbanization in Xi'an, we selected the proportion of construction land, the proportion of farmland, and a landscape fragmentation index of each Jiedao in Xi'an to define the boundary of the urban fringe of Xi'an, and obtained a land use data set of the urban fringe in Xi'an (2015). This data set not only provides a method for defining the urban fringe, but also provides a reference for land use planning and urban development in the study area.

2 Metadata of Dataset

The name, author, geographical region, data year, data set composition, data publishing and sharing service platform, and data sharing policy of the land use data set of the urban fringe in Xi??an (2015) are listed in Table 1.

3 Data Development Method

3.1 Raw Data

The urban fringe boundary data in this data set are from the Shaanxi Bureau of Surveying, Mapping and Geoinformation, and land use data are from Landsat TM images in the Geospatial Data Cloud (http://www.gscloud.cn)^[7] and Google Earth images. All data are from 2015.

3.2 Algorithm Principle

(1) This data set uses Landsat TM remote sensing images and Google Earth images as its main data sources. After image fusion, geometric correction, and image clipping, we overlay the administrative boundary data of each Jiedao to Landsat TM images and digitalized the land use status of each Jiedao in Xi'an city and its adjacent areas using a human-computer interactive visual interpretation method. We then divided the land use types into four categories: construction land, farmland, forest land, and other land, and obtained a vector map of land use in Xi'an City.

(2) Based on the land use data, we determined the proportion of construction land and farmland in each Jiedao. Then we converted the vector data of land use into raster data and input it into Fragstats 4.2 software to calculate the fragmentation index of construction land and farmland of each Jiedao.

(3) In combination with the spatial development trend of Xi'an urbanization, land use status, the proportion of construction land and farmland, and a landscape fragmentation index of each Jiedao, we defined the boundary of the urban fringe, and finally obtained a land use data set of the urban fringe in Xi??an.

Table 1  Metadata summary of the land use data set of the urban fringe in Xi'an (2015)

4 Results

4.1 Composition of Dataset

The land use data set of the urban fringe in Xi'an (2015) consists of two parts: (1) boundary data of the urban fringe in Xi'an (.shp); and (2) land use data in the urban fringe of Xi'an (.shp). The spatial distribution results are shown in Figure 1.

4.2 Analysis of Data Results

The urban fringe area of Xi'an includes 25 Jiedao belonging to the Baqiao, Chang'an, Yanta, and Weiyang Districts and Fengdong New Town, with a total area of 1425.22 km². Compared with the core areas that have fully realized urbanization, these 25 spatial units still have certain amounts of farmland, and the agricultural and urbanized spaces are intertwined and mixed. Statistical information regarding the land use in each Jiedao is given in Table 2.

Table 2  Area of different land uses in the urban fringe in Xi'an??km²??

The main land use types in the urban fringe of Xi'an in 2015 were farmland and construction land, with an area of 521.40 km²and 572.52 km², accounting for 38.05% and 41.78% of the total area, respectively. Dazhao Jiedao had the largest farmland area (39.93 km²). The farmland area of Hongqing, Dizhai, Xinhe, Xiliu, Duqu, and Paoli Jiedaos also exceeded 30 km². However, the area of construction land in Weiqu, Guodu, LiucunBao, Hancheng, and Sanqiao Jiedaos exceeded 30 km². The largest forest land area was Hongqing Jiedao (22.92 km²). Forest land was also relatively abundant in Hongqi, Xiwang, Dizhai, and Wangqu Jiedaos. The other land area of Caotan Jiedao was 28.43 km², with most of the land being a large water area.

From the perspective of the proportion of land use, the largest proportion of construction land (>80%) was in Sanqiao Jiedao. The proportion of construction land in Hongqi, Weiqu, Guodu, Dengjiapo, Yuhuazhai, Liucunbao, and Hancheng was also over 50%. This indicates that these areas were strongly influenced by urbanization and were rapidly becoming urban built-up areas. In contrast, the proportion of farmland in Huangliang, Xiliu, Wuxing, and Duqu was still over 50%, which indicates that the urbanization process has been relatively slow due to the distance from the urban center.

4.3 Description of Data Results

This data set is based on Landsat TM images, with a resolution of 30 m. The resolution of the images is slightly coarse. Even with the assistance of Google Earth images, there are still some errors in the results. In addition, the data set only classifies land use types into farmland, construction land, forest land, and others in the interpretation process, the classification of which is comparatively general. There are still some areas of water and grassland in the urban fringe, and there are numerous types of construction land. To determine land use changes in the urban fringe in Xi'an more intuitively and accurately, multi-period SPOT and Landsat TM images, with higher resolution, should be used for land use interpretation in the future. This will enable an assessment of exactly what type of construction land the farmlandhas been converted into in the urban fringe and will enable the dynamic changes of land use to be determined, therefore providing a reference for future urban land planning.

5 Discussion and Conclusion

The urban fringe is located between the two systems of the "city" and "country.?? It is the most sensitive, influential, and rapidly changing area during the process of urbanization. The most prominent feature of the urban fringe is that the land use situation is complex and changes rapidly, which makes urban land use planning difficult. This data set makes use of Google Earth images to classify and interpret Landsat TM images of the Xi'an urban area and its adjacent areas in 2015 to obtain land use data. By combining this information with the spatial development trend of urbanization in Xi'an, we selected the proportion of construction land and farmland, and a landscape fragmentation index for each Jiedao in Xi'an to determine the boundary of the urban fringe, and finally obtained a land use data set of the urban fringe in Xi'an (2015). From the results, it was apparent that the closer the Jiedao was to the city center, the more severely it was affected by urbanization. A large area of farmland in these Jiedaos had been transformed into urban construction land, and the degree of landscape fragmentation was also higher. The Jiedaos far from the city center were relatively weakly affected by urbanization, and still had a high proportion of farmland. The development of this data set provides a method to determine urban fringe areas. In addition, the data set itself also provides support for relevant research and urban land use planning in Xi'an.

Author contributions

Huang, X. J. designed the development of the data set; Wang, C. and Hu, K. L. collected and processed data; and Wang, B. wrote the paper.

References

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[5]       Huang, X. J., Wang, C., Hu, K. L., et al. Land use data set of urban fringes in Xi??an (2015) [DB/OL]. Global Change Research Data Publishing & Repository, 2019. DOI: 10.3974/geodb.2019.04.08.V1.

[6]       GCdataPR Editorial Office. GCdataPR data sharing policy [OL]. DOI: 10.3974/dp.policy.2014.05 (Updated 2017).

[7]       Geospatial Data Cloud site, Computer Network Information Center, Chinese Academy of Sciences. (http://www.gscloud.cn); Image track number is P127 / R36. DOI: 10.3974/dp.policy.2014.05.txt