Abstract
The spiritual connotation of contemporary cities has gradually become rich and colorful, and the concept of a green city has also been accepted by the public. People living in cities have higher and higher requirements for landscape, but traditional landscape design cannot achieve efficient and accurate planning. Therefore, the old design method, which cannot meet the complex and changeable urban needs and cannot keep up with the development and changes of the times, is doomed to be eliminated and replaced. This study introduces a GIS system and uses an AHP method to assist landscape design. Through rational resource utilization of topography, vegetation growth, population density, and other conditions, the city can be green and environmentally friendly, reduce energy consumption, and meet people's concept of healthy life. The experimental results show that: (1) through the GIS system, a multidecision model is constructed to choose a reasonable location for the garden. Based on the opinions and scores of all parties, the B place with a score as high as 8.97 was selected. (2) Using comprehensive landscape sensitivity to divide four levels of landscape land-use value and looking for the best landscape vision, it is divided into five scenic functional areas and 12 scenic spots. SPEI and NDVI were used to select cultivated plants and landscapes. (3) Route multifactor comprehensive model is designed to plan garden route. The coincidence degree between the model and the actual road condition is about 87.62%. Citizen satisfaction is between 7 and 9 points, and the comprehensive evaluation is high. (4) The evaluation system of landscape architecture, in which both B-level index and C-level index are higher than 7 points is constructed, which is in line with the expectations of the public and experts and convenient for feedback correction. The method based on this study is feasible and can be further optimized.
1. Introduction
In recent years, the propaganda of green urbanism can better help people know, understand, and build the cities they have lived in for generations. On the basis of a deep understanding of the green city and the integration of the essential characteristics of landscape architecture design, the ultimate goal is to make people and nature achieve a harmonious and unified realm. At present, there are a lot of documents about the application of urban planning and design, which can provide us with more methods for reference. Compact urban areas can be identified by using GIS and AHP, and the function and spatial structure can be fully developed [1]. The spatial distribution data were extracted by GIS and ENVI software to evaluate the natural suitability of the environment [2]. The GIS system is introduced to make the spatial accuracy error less than 4%, and the urban landscape planning and design under light pollution are completed [3]. Further, introducing high-resolution image recognition technology can obtain data more effectively and simulate the green city landscape platform [4]. In addition, GIS remote sensing information collection can effectively monitor the ecological environment quality [5]. The evaluation thinking framework based on the entropy method and GIS can comprehensively evaluate the general situation of green cities [6]. Modeling cities was based on GIS to reduce energy consumption and greenhouse gas emissions [7]. To meet the special needs of landscape management, the landscape GIS system should improve the manageability of each area [8]. Mediterranean Green City uses GuidosToolBox software, GIS modeling technology, and MSPA to evaluate the connectivity of the natural framework [9]. Taking the design of Libo World Natural Heritage Theme Park in Karst of South China as an example, this study analyzes the application advantages of the GIS system [10]. The route selection of scenic roads in mountainous areas of southern Anhui by GIS–AHP method conforms to the development of transportation planning and tourism and recreation [11]. The ecological sensitivity of Qingcheng Mountain–Dujiangyan scenic spot under the construction pressure was evaluated by GIS [12]. Based on RS and GIS, combined with DEM and remote sensing image data, the ecological risk of Emei Mountain Scenic Area was analyzed and evaluated [13]. This study briefly summarizes the application of GIS in landscape architecture in the past 30 years [14]. Appropriate ideological and political education elements were incorporated and the course of GIS technology application in landscape architecture was reformed [15].
Since science and technology have never been valued by traditional art design, they are often despised or even ignored. Therefore, the landscape design relying on computers was not optimistic at first. The above literature boldly breaks through the limitations and abandons the single messy and blind pursuit of the inspiration construction method. Using various angles and technical methods to design landscape, we try to scientifically discuss the construction of a green city and related decision-making and scheduling. Combining landscape design with modern science and technology through powerful computer technology, the actual scene is better conceived and designed, and the traditional design is revolutionized so that it retains the original landscape design characteristics, and at the same time, it is more diversified, inclusive, and a true complex. Due to its strong logic, easy to use, powerful data processing function, and many other advantages, the GIS system has been gradually introduced into landscape design and has brought new value and scientific achievements. This study presents a GIS system, which uses the AHP method to assist landscape design. Through the rational utilization of resources in topography, vegetation growth, population density, and other conditions, the city can be green and environmentally friendly, reduce energy consumption, and meet the concept of people's healthy life. Through the GIS system, a multivariate decision-making model is built, and a comprehensive landscape sensitivity to divide four levels of landscape land use value is used to find the best landscape vision. SPEI and NDVI are used to select cultivated plants and landscapes. The evaluation system of landscape architecture is constructed, and the B-level index and C-level index are both higher than 7 points, which meets the expectations of the public and experts and is convenient for feedback correction. The method based on this study is feasible and can be further optimized.
2. Related Works
2.1. Green City
For Green City [16], in the theory of urban sustainable development, energy is used. For a prosperous and developing city, the uncontrolled and high-speed development of the city will inevitably cause a series of injuries to the natural living environment. It is a theory put forward in the “Green Movement,” aiming at protecting the environment. In the theory of urban sustainable development, the use of energy can further promote the stable development of the economy. Designing a garden landscape in the city is just in line with the spiritual connotation of the green city. Great importance is attached to the neglected natural resources in cities and rational transformation and utilization are made so as to drive more sustainable economic development through the landscape. This is in line with the requirements of ecological balance advocated in green cities.
Problems such as environmental pollution, insufficient resources, and serious losses are becoming more and more serious, which cause irreversible harm and threat to human survival and development. Therefore, the traditional development concept in the past needs to be changed. A more reasonable ecological environment is constructed, and resources are used better. Man and nature are harmonious and unified, and the goal lies in the common development of economy and environment. While protecting nature, it drives the economy and emphasizes the overall balance of ecology. To try to point out the future and direction of people's healthy life and civilized development, scholar Timshi Bitley summed up several characteristics of green cities, as shown in Figure 1:
2.2. Urban Landscape Architecture
The normal operation of the city will inevitably transform the original natural landscape. At this time, how to coordinate people, urban architecture, and natural landscape has become a problem that people should think about. Landscape architecture was born. By using this kind of planning, people can better coordinate the relationship between the living environment and natural science. Designers strive to create an efficient, comfortable, safe, and healthy living environment for people living in this land. For cities, it is of great significance.
The core of traditional urban garden design lies in artistic literariness. Designers are easily limited by individuals in the process of design and planning and they pay great attention to the generation of inspiration. The creation of artistic conception and the interest in poetry and painting are the soul of garden creation. Therefore, people will have a prejudice in the design of gardens. That is, this kind of planning and design is not logical and scientific, and cannot be measured concretely by parameters. This leads to the late integration design of modern science and technology with this discipline, which lags behind and has a broad prospect. However, to adapt to the complex and changeable social needs, the traditional landscape design system can not meet the requirements and can not reasonably explain the logic and internal relations of landscape design, breakthrough the traditional cognitive concept and create digital aesthetics. Let all landscape elements interweave harmoniously to create a scientific and dynamic garden system.
2.3. GIS Technology
GIS [17], the Chinese name is Geographic Information System. This is a computer system based on geographic information and spatial database that was gradually developed in the 20th century. It can collect and sort out the scattered spatial data (map data, remote sensing data, statistical data, etc.) and analyze and build a geographical model. This reduces a lot of tedious and unnecessary field exploration work and capital loss and greatly improves the work efficiency of the designers. As an instrumental subject, it has a wide range of uses, such as transportation, environmental protection, agriculture, and these industries, through the use of the GIS system for spatial analysis, can be associated with spatial location and attribute relationship, showing a three-dimensional spatial relationship. ArcGIS is the mainstream GIS platform software in the market so far, and it is a mature and complete product, as shown in Figure 2:
In ArcGIS operation, several kinds of data are involved, as shown in Table 1:
2.4. Analytic Hierarchy Process
AHP [22], whose Chinese name is “analytic hierarchy process,” combines qualitative and quantitative analysis when dealing with complex decision-making problems. This method is simple and clear, and the basic idea of solving problems is similar to people's way of thinking, especially the process of judgment is roughly the same. The basic steps of AHP are as follows:
2.4.1. Establish Hierarchical Structure Model
It is expressed by a structural model with clear levels. All the factors that need to be considered into the model are put, which can be divided into: the highest level, the middle level, and the lowest level.
2.4.2. Constructing Paired Comparison Matrices
Among them, let n elements participate in the comparison, and the relative weight is used to describe the comparison of the importance of a certain factor between the i-th element and the j-th element.
We can get the characteristics of paired comparison matrices:
2.4.3. Consistency Test
Theoretically, if it is an identical paired comparison matrix, then
In case of inconsistency, the following indicators are calculated:
Among them, RI is only related to the matrix order n, which can be obtained by specific query.
Judgment method: when there is only , the inconsistency degree of paired comparison matrix is satisfactory and can be accepted; otherwise, we will continue to adjust the pair comparison matrix until we are satisfied.
The method of calculating the maximum eigenvalue of paired comparison matrices:
2.4.4. Hierarchical Total Sorting [23]
For example, after a series of calculations in the previous three steps, are sorted to give a decision.
2.5. NDVI and SPEI
NDVI [24], the Chinese name is normalized vegetation index. Using this index in this study, we can reflect the coverage degree of surface vegetation and the growth of vegetation; at the same time, it is also one of the important indicators reflecting the growth and nutrition information of crops. In the calculation process, the spectral reflection characteristics of different bands are mainly used. If NIR is the reflection value in the near infrared band and R is the reflection value in the red band, the definition formula of normalized vegetation index can be obtained as follows:
The range of NDVI values is [-1, 1]. A positive value represents plant coverage, and the greater the calculated NDVI value, the greater the vegetation density; the smaller the NDVI value, the smaller the vegetation density. Therefore, in this study, we can reasonably choose suitable plants for cultivation in gardens according to the monitored vegetation coverage, which is of great significance. Of course, it is not completely appropriate for practical application to calculate only by definition. Therefore, there are several NDVI estimation models as follows:
2.5.1. Modis Algorithm [25]
2.5.2. TM/ETM Algorithm
2.5.3. AVHRR Algorithm
We can use the standardized precipitation evapotranspiration index (SPEI) to assess the temporal and spatial effects of drought on soil wetness. The larger the SPEI value, the wetter the area is. The smaller the value, the drier the area. It can provide great reference significance when selecting plants.
3. Landscape Design Based on GIS
According to the goal of green city, the overall design is carried out, and the urban landscape elements are analyzed by using ArcGIS software in GIS system. It is necessary to consider the site selection and specific functions of scenery, the flow of vehicles and people, and the convenience of transportation are also necessary to consider the integration and coordination between the landscape architecture and the surrounding environment, and the selection of plants in the landscape. After considering all the above factors, it is necessary to use the AHP method to evaluate the whole landscape concretely, and the designer will make corresponding adjustments and designs for landscape planning according to the feedback obtained.
3.1. Location Model
Landscape planning needs to choose a suitable geographical location in the city. Due to the complexity of the spatial layout, we usually simplify and eliminate unnecessary related objects, establish a clear model, and carry out specific analysis process in this model.
3.1.1. Scale Model
where is the total number of existing facilities in the study area and is the total number of required facilities.
3.1.2. Distance Model
where is the distance from the facility supply position to the service demand position. Satisfaction means reasonable spatial layout.
3.1.3. Location Allocation Model
where is the weight of the i-th demand point; is the distance; is the decision variable. The ultimate goal is to find the minimum value of the objective function, that is, the minimum weighted distance.
Three spatial models are compared, as shown in Table 2:
In view of the shortcomings of the three models the problems we need to solve were , cleared and finally we choose to build a multicriteria decision-making location model based on the GIS system. Based on the GIS system and the method of investigation and demonstration, Dijkstra algorithm is used to solve the shortest path, and a single optimal address is obtained through a series of solutions, as shown in Figure 3:
Shortest path:
Build a mathematical model:
where G is a tree and the solution is simple:
G is a general network, which is complicated to solve:
3.2. Garden Route Design
Determining the road route is the most important basic work to connect the whole landscape. Therefore, we need to give full consideration to the road route arrangement of urban landscape. To fully consider a variety of factors that can affect the road, it must be reasonable in the economy and also ensure green environmental protection. The whole garden keeps coordination in the environment and finally achieves the goal of people-orientation. Using the powerful function of the computer to choose the most suitable garden route, reduce the investment of capital cost and the waste of manpower and material resources. As shown in Figure 4:
Four single factors related to road route determination are considered comprehensively. The weight of each factor is determined by the analytic hierarchy process and expert consultation. On this basis, using GIS system, the map of each topic is analyzed by weight superposition, and the comprehensive cost model is established. Finally, through this model, the optimal route design is selected. Using the Raster Calculator function of ArcGIS software and Spatial Analyst module. Calculation model:
Based on the raster data, the optimal road path is analyzed. Mathematical model:
3.3. Landscape and Architectural Analysis
When the landscape architecture is built, the original ecological environment in the city will be destroyed. To conform to the spirit of green urbanism, the designers in this study can measure the conspicuous degree of landscape and the clarity of attention with the help of a landscape sensitivity method. The most valuable ecological features to the greatest extent are preserved, people are shown the best landscape vision, and people are let enjoy the beautiful scenery of the garden. In addition, to coordinate construction and protection, we also need to pay attention to the height of buildings and landscape buildings around the city and architectural planning with the help of the GIS system.(1)Slope landscape sensitivity(2)Distance landscape sensitivity(3)Visual probability landscape sensitivity(4)Comprehensive analysis of landscape sensitivity
“Plants” are the most important part of landscape composition. The landscape in the garden is not single, and the actual terrain is complex. The choice of plants should adapt to local conditions and follow the general law of plant growth. With the help of the GIS system, factors such as light, temperature, moisture, and soil are fully considered, and indicators such as NDVI and SPEI are used to provide scientific suggestions for the scientific cultivation of plants so that plants can grow and form beautiful landscapes. As shown in Table 3:
3.4. Construction of the Evaluation System
It is very important to construct the evaluation system of landscape architecture for the evaluation and optimization of landscape architecture ability. Function expression:
We set the following landscape evaluation indicators. As shown in Table 4:
4. Experimental Analysis
The experimental project of this study is to create a natural landscape that meets the requirements of a green city in a city. It is necessary not only to meet the needs of citizens for daily play and recuperation but also to show the city's characteristic culture, pay attention to the ecological harmony between man and nature, and give the city a green leisure comprehensive scenic spot.
4.1. Reasonable Degree of Site Selection
A suitable place is chosen in the city for garden transformation. According to geography, space, length, topography, convenient transportation, and other factors, the experiment uses the multidecision site selection model based on the GIS system and gives three garden site selection sites: A, B, and C. The location of these three locations in the city environment is a relatively good place, and then through expert interviews and public questionnaires, we carried out the evaluation of the reasonable degree of site selection, as shown in Figure 5:
We use the 10-point scoring standard to comprehensively evaluate the scores of models, experts, and citizens, and find that the comprehensive scores of A, B, and C are about 8.81, 8.97 and 8.53. Among them, location B scored the highest; among the scores given by models, experts, and citizens. Location B is also the most popular and the best choice location.
4.2. Master Plan of Landscape Architecture
4.2.1. Landscape Sensitivity Synthesis
According to the GIS system and relevant design experts, the weights of slope landscape sensitivity (Sa), distance landscape sensitivity (Sd), and visual probability landscape sensitivity (St) can be determined As shown in Figure 6:
According to the comprehensive landscape sensitivity (S) stratification in each class, we can divide the landscape sensitivity areas in the landscape, as shown in Table 5:
All the land in the garden planning area is divided according to the classification table. We can clearly see the different sensitivity levels in different regions, as shown in Figure 7:
The higher the sensitivity of landscape, the more scenery tourists see and the more it is suitable for sightseeing. Class I landscape sensitive areas account for 35.10% of the total planned garden area, and basically the best viewing areas are all over the two sides of the road. Among them, the sensitive land area of scenic appreciation area is as high as 14.80%. Class II and Class III landscape sensitive areas are mainly scenic sightseeing and cultural entertainment areas, accounting for 33.70% and 26.60% of the total planned garden area respectively. Level IV area is only 5% of the land area, scattered in various areas, with the lowest viewing value, which is difficult to be developed and visited.
4.2.2. Landscape Functional Zoning
According to the needs of gardens, based on the original mountain vegetation and water flow area, most of the mountains and ecological landscapes are preserved, such as digging and starting work are reduced and the damage to the soil and vegetation is minimized. It is divided into the following five regions (12 landscape spots in total): (1) building area: the areas with a poor environment are developed into building areas, artificial greening, and cultivation are used to restore the environment, and the landscape effect and atmosphere are set off by combining human landscape. (2) Cultural and entertainment areas: at the same time, exhibition education with cultural characteristics will be carried out, and activity areas for citizens to play and recuperate will be developed. (3) Economic and industrial zone: the land with great economic utilization value will be developed into an economic and industrial zone to drive the economic development of the city. (4) Ecological restoration area: natural protection and ecological restoration are carried out for some landscapes that have no development value but have been ecologically damaged. (5) Landscape appreciation area: transform the remaining landscape for viewing and sightseeing, as shown in Figure 8:
4.3. Facilitation Analysis of Route Design
Based on ArcGIS software and route multifactor comprehensive model, we got the total design of the garden route in this experiment. As shown in Figure 9:
To explore the rationality and convenience of route setting in more detail, we measure the coincidence between the specific actual road condition construction and the route given by the model and the route selected by experts. Twelve landscape spots were set for wiring, and the feelings of citizens in five groups (200 people in each group, 1000 people in total) were comprehensively considered, as shown in Figure 10:
We can find from Figure 10 that the garden route given by the model is the most consistent with the actual road conditions, with a coincidence degree of about 87.62%, while the coincidence degree of the route given by experts is about 81.81%. Their average coincidence was 84.71%. This shows that the optimal path given by the model through multi-factor consideration is effective and feasible, and has a high practical value.
With the 10-point scoring system, each citizen has different situations, so his subjective evaluation is different. The comprehensive score for each landscape spot is between 7 and 9 points. This shows that the route setting basically meets the travel needs of citizens, as shown in Figure 11:
4.4. Vegetation Analysis
We count the SPEI trend and NDVI of the landscape planning area in the past 10 years, as shown in Table 6:
NDVI in recent 10 years from 2011 to 2020. The plant cover in the scenic area and the economic and industrial area increased with the increase in the number of years, indicating that precipitation and vegetation grew well. However, the plant coverage in ecological restoration areas and building areas decreases sharply, and the environment is harsh, as shown in Figure 12.
Therefore, in terms of plant selection, we mainly choose drought-resistant, wind-resistant, and sun-loving plants in ecological restoration areas and building areas to stabilize water and soil and restore the original ecological environment. For other areas, we choose to keep the original tree species and plants without making too many ecological changes. More water-resistant plants can be planted in water flow areas, while flower lawns and sparse forest landscapes can be created in flat areas.
4.5. Evaluation and Analysis
The indexes in the evaluation system of landscape architecture are scored. Citizen scores are generally higher than expert scores. In the comprehensive score, the score of the ecological benefit index is the highest, up to 9 points, which shows that gardens give people real comfort for landscape design and ecological protection. The aesthetic experience index is as high as 8.2, and aesthetics has been recognized by experts and the public. The score of behavior feeling is 7.9, which is slightly lower and should be given more attention and changes. The effect of social function is the worst, with a score of 7.2, and related facilities and equipment should be further improved in the follow-up. The C-grade index scores are all greater than 7 points, which shows that it basically meets the requirements of landscape design, and has been generally recognized by experts and the public in rationality, as shown in Figures 13 and 14:
5. Conclusion
In this study, the concept of green city is integrated into landscape design and the GIS system is used to improve the original traditional design method, which has a strong innovative concept. The research results of this study show the following:(1)To choose a reasonable landscape location for a city, it is necessary to build a multidecision site selection model through the GIS system. Taking full account of the opinions and scores of experts, models, and citizens, the B site with a score as high as 8.97 is selected as the site selection for landscape design from three sites: A, B, and C.(2)Using comprehensive landscape sensitivity to divide the land use value. The garden area is divided into four levels, and the functions of the different sensitive levels are different, so as to find the best landscape vision. Following the general law of ecological environment, five scenic functional areas and 12 landscape spots are divided. According to SPEI and NDVI, the cultivated plants and landscapes were selected.(3)design a multifactor comprehensive model of the garden route and give the master plan of the garden route. According to the actual road conditions, the rationality and convenience of the route is explored. The coincidence degree of the model is about 87.62%, and the effect is very good. Citizens' satisfaction with the route is between 7 and 9 points, and the comprehensive evaluation is high.(4)construct a landscape evaluation system with 4 B-level indexes and 17 C-level indexes. Both B-level index and C-level index are higher than 7 points, which is in line with the expectations of the public and experts. Subsequent optimization can be optimized and fed back according to index details.
The final experimental results prove the feasibility and superiority of this method. Although GIS technology has been widely used, relying solely on the use of the GIS system for landscape design will cause aesthetic defects. This requires the designer to measure subjectively. In addition, due to the problem of network security, the GIS system should also strengthen the security work to avoid the risk of data leakage caused by some interference factors.
Data Availability
The experimental data used to support the findings of this study are available from the corresponding author upon request.
Conflicts of Interest
The authors declare that they have no conflicts of interest regarding this work.