城市扩张是近年来全球变化研究的热点课题，随着3S技术的快速发展，尤其是遥感（RS）和地理信息系统(GIS)技术在分析全球土地利用信息方面的便捷应用，使得城市扩张在土地利用领域的研究愈发深入。城市群是城市到达一定阶段后的重要形式，是城市扩张研究领域的重要内容，对于研究城市发展规划和制定发展策略具有重要意义。城市群的时空演变特征是其城市定位、空间组织、发展趋势的重要表征，对于城市的进一步研究具有重要作用。因此，基于RS和GIS技术综合分析城市群的扩张规律和时空异质性特征对于未来城市发展规划和城市扩张科学研究具有重要意义。

本文以关中平原城市群为研究区域，采用GIS空间分析与景观指数分析相结合的方法，选取了2005年、2010年、2015年、2020年4期Landsat遥感影像，运用CART决策树分类方法，综合光谱特征、纹理特征、植被、水体和建筑指数，提取关中平原城市群的土地利用信息，并计算了5种景观指数，结合近年来的社会经济数据，分析城市群各地类的占比以及城市扩张的强度、速率、模式、景观格局变化情况，并比较了城市扩张过程中时空特征的异同，总结城市群扩张规律，进而对城市群未来的扩张趋势进行预测，最后提出对城市群未来发展具有建设意义的策略。全文主要结论如下：

（1）关中平原城市群建设用地占比较小，呈缓慢增加趋势，整体增长率偏低，扩张强度先快后慢。第一大土地覆盖类型为林地，其次为耕地和建设用地，其中建设用地占比仅达到12%左右；3省份建设用地占比为山西省＞陕西省＞甘肃省；11个市建设用地占比较高的为西安市、庆阳市、咸阳市、渭南市、运城市，均为城市群中部和东部较发达城市，西部城市占比较小；2005-2020年城市群建设用地增长面积为3637.37km²，涨幅在30%左右，平均增长率仅为2.32%，各城市最大增长率3.53%，最小增长率仅为0.44%，增长相对缓慢。并且前期增长率大于后期增长率，扩张强度也呈现出先快后慢的趋势。

（2）景观格局方面，关中平原城市群景观格局整体变化相对较小，各个城市间存在差异，时间尺度上符合“扩散-聚集”的城市发展普遍规律。西安、咸阳、渭南、宝鸡、运城、庆阳6市城市结构相对其他城市较稳定，城市紧凑度较高，在扩张模式上以边缘式为主。平凉、天水、铜川、商洛4市由于地理位置限制，城市景观格局的稳定度低，聚集度低，扩张模式中飞地式占比较高，这也符合城市发展与城市扩张的正比关系。

（3）城市群扩张规律在时间和空间两个尺度上存在不同的特点。时间上，一是起始年份建设用地面积较大的城市，在其后15年间建设用地增长面积较多；二是不论城市规模的大小，15年间建设用地扩张都呈现出先快速增长再缓慢增长的的趋势；三是，扩张速率和扩张强度随着城市规模的增大，逐渐变得缓慢；四是景观格局随着城市扩张，逐步趋于稳定，形状更复杂，聚集程度增加，整体破碎度减小；空间上，一是城市群涉及省份所包含的城市数量在一定程度上决定城市建设用地扩张量，包含数量越多，对城市扩张贡献值越大；二是城市群发展不平衡，主要城市的扩张起绝对主力作用，其他城市对扩张的影响力微乎其微；三是关中平原城市群扩张的主要方向在城市群的中东部，且基本为一条交通干线上的几大城市。

（4）城市群未来的扩张在扩张方向、模式、规模、速率、强度方面随着驱动力因素的变化而发生改变。扩张方向会集中在中东部地区，沿陇海线及京昆线向东扩张，扩张强度依次减弱，扩张速率中东部逐渐减小，西部逐渐增大，扩张规模中东部会高于西部，城市群空间结构的扩张趋势预测会整体按照“一圈一轴三带”的模式发展，外围按点状城市分布的模式发展；定量预测2030年建设用地面积增加最多的是西安市，最少的是铜川市，而关中平原城市群整体的增加量在10%-18.9%。鉴于以上预测，提出了优化城市结构、调整产业结构、构建综合城市交通和深度参与一带一路建设四点城市群发展策略，对于城市群未来的空间发展规划具有一定的借鉴意义。

Urban expansion is a hot topic in global change research in recent years. With the rapid development of 3S technology, especially the convenient application of RS and GIS technology in analyzing global land use information, the research on urban expansion in the field of land use has become more and more in-depth. Urban agglomeration is an important symbol of a certain stage of urban development, an important content in the field of urban expansion research, and is of great significance for studying urban development planning and formulating development strategies. The temporal and spatial evolution characteristics of urban agglomerations are important characterizations of their urban positioning, spatial organization, and development trends, and play an important role in the further study of cities. Therefore, a comprehensive analysis of the expansion laws and spatiotemporal heterogeneity characteristics of urban agglomerations based on remote sensing and geographic information technology is of great significance for future urban development planning and urban expansion scientific research.

This paper takes the Guanzhong Plain urban agglomeration as the research area, adopts the method of combining GIS spatial analysis and landscape index analysis, selects four Landsat remote sensing images in 2005, 2010, 2015, and 2020, and uses the CART decision tree classification method to synthesize spectral characteristics, Texture features, vegetation, water bodies, and building indices were used to extract the land use information of the Guanzhong Plain urban agglomeration, and 5 landscape indices were calculated. Combined with socioeconomic data in recent years, the proportion of each type of urban agglomeration and the intensity of urban expansion were analyzed. , rate, pattern, landscape pattern changes, and compared the similarities and differences of time series characteristics in the process of urban expansion, summarizes the expansion laws of urban agglomerations, and then predicts the future expansion trend of urban agglomerations, and finally puts forward the construction significance for the future development of urban agglomerations strategy. The conclusion of the full text is as follows:

(1) The proportion of construction land in the Guanzhong Plain urban agglomeration is small, showing a slow increase trend, the overall growth rate is low, and the expansion intensity is first fast and then slow. The largest land cover type is forest land, followed by cultivated land and construction land, of which construction land accounts for only about 12%; the proportion of construction land in 3 provinces is Shanxi Province > Shaanxi Province > Gansu Province; 11 cities account for construction land comparison The highest are Xi'an, Qingyang, Xianyang, Weinan, and Yuncheng, all of which are relatively developed cities in the central and eastern part of the urban agglomeration, and the western cities account for a smaller proportion; The growth rate is around 30%, the average growth rate is only 2.32%, the maximum growth rate of each city is 3.53%, and the minimum growth rate is only 0.44%, the growth is relatively slow. And the growth rate in the early stage is greater than the growth rate in the later stage, and the expansion intensity also shows a trend of fast at first and then slow.

(2) In terms of landscape pattern, the overall change of the landscape pattern of the Guanzhong Plain urban agglomeration is relatively small, and there are differences between cities. The time scale conforms to the general law of urban development of "diffusion-aggregation". The urban structure of Xi'an, Xianyang, Weinan, Baoji, Yuncheng, and Qingyang is relatively stable compared with other cities, and the urban compactness is relatively high. There are three expansion modes (edge type, enclave type, and filling type), and the edge type is the most host. Due to geographical constraints, Pingliang, Tianshui, Tongchuan and Shangluo have low stability and low agglomeration in their urban landscape patterns, and enclaves account for a high proportion of the expansion model, which is also in line with the proportional relationship between urban development and urban expansion.

(3) The expansion laws of urban agglomerations have different characteristics in time and space. In terms of time, firstly, cities with a larger area of construction land in the initial year have more area of construction land growth in the following 15 years; secondly, regardless of the size of the city, the expansion of construction land in the 15 years has shown a rapid growth at first and then a slow growth. The third is that the expansion rate and the expansion intensity gradually become slower with the increase of the city scale; the fourth is that the landscape pattern gradually becomes stable as the city expands, the shape is more complex, the aggregation degree increases, and the overall fragmentation degree decreases. Small; in terms of space, first, the number of cities included in the provinces involved in the urban agglomeration determines the expansion of urban construction land to a certain extent. The more the number of cities involved, the greater the contribution to urban expansion; The expansion of major cities plays an absolute main role, and other cities have little influence on expansion. Third, the main direction of the expansion of the Guanzhong Plain urban agglomeration is in the central and eastern parts of the urban agglomeration, and it is basically several major cities on a traffic trunk line.

(4) The future expansion of the urban agglomeration will change with the changes of the driving factors in the expansion direction, mode, scale, speed and intensity. The expansion direction will be concentrated in the central and eastern regions. It will expand eastward along the Longhai Line and the Beijing-Kunming Line. The expansion intensity will gradually weaken. The expansion rate will gradually decrease in the central and eastern regions, and gradually increase in the western regions. The expansion trend of the structure is predicted to develop in accordance with the model of "one circle, one axis and three belts" as a whole, and the periphery will develop in the mode of point-like city distribution; it is quantitatively predicted that in 2030, the construction land area will increase the most in Xi'an, and the least in Tongchuan. The overall increase in the Guanzhong Plain urban agglomeration is 10%-18.9%. In view of the above predictions, a four-point urban agglomeration development strategy is proposed to optimize urban structure, adjust industrial structure, build comprehensive urban transportation, and deeply participate in the construction of the Belt and Road, which has certain reference significance for the future spatial development planning of urban agglomerations.