Spatial pattern analysis and identification type of open green space in Yogyakarta city

. Open green Space is a spatial plan model aiming to maintain the quality of the environment. Nowadays, the number and distribution of Open green Space have decreased, particularly in urban areas. Such decline is due to many reasons, one of which is land conversion caused by social activities. This research aimed to analyse the distribution pattern and identify the type of Open green Space in Yogyakarta City. The method in this study using moran's I Index approach, GIS and direct field review. The results showed that the Open green Space was clustered with Moran’s Index of 0,074594. Validation with field check indicated that there was an absence of even, thorough, and most recent Open green Space identification. Visual detection using high-resolution satellite images and aerial photos affirmed that many open green spaces had not been inventoried, justifying the need for data update in Yogyakarta City. The identification process resulted in different types of Open green Space, but the most widely distributed ones in Yogyakarta City were in the forms of Private yard, Office park, Green belt, and City Parks.


Introduction
Regional development is an effort to maintain and improve people's welfare. Its principle is expected to take into account some vital elements such as ecology [1][2][3] culture [4,5] energy [6][7][8][9] natural resources [10] and community participation [11][12][13]. The integration of these elements creates sustainable regional development. Urban area is a space that experiences a very rapid development, which most of the time results in unbalanced urban growth [14]. For a sustainable urban growth, the development has to be planned with an accurate target according to the characteristics of the region.
The characteristics of a region significantly determine the implemented regional development planning policy. A thorough comprehension of these properties leads to maximum and efficient extraction and utilization of local potentials and resources. Regional development planning has to consider environmental condition and quality [15,16] One step to maintain the environmental quality in the development is by opening access to the arrangement of open green space [17]. Open green spaces in urban areas are recognized as valuable for the benefits they provide, such as biodiversity conservation and spaces for people to relax [18] In addition to maintaining the quality of the environment, open green space can also be used as a place of recreation [19,20]. It is also applicable as disaster mitigation measures [21] for air pollution disasters [22][23][24], floods [25,26], and drought [27] In term of air pollution, open green space serves as the design of an area used for green plants, which filter solid particles that can cause air pollution. It can be functioned to maintain groundwater availability to avoid any potentials of drought disaster. Furthermore, it can also stabilize the temperature in a region [28].
In general, sustainable development can take place by considering some of the main pillars namely, social, environmental and economic. The interaction of the three pillars can have positive and negative effects in an urban area (Figure 1.). Open green space in urban areas is the primary requirement for ecological balance and, thereby, human welfare [30]. Purpose of this research, is analyzed the distribution pattern and identified the type of open green space in Yogyakarta City, i.e., one of the urban areas with rapid development in the Special Region of Yogyakarta

Method
This research used both primary and secondary data. The primary data were the results of field survey that identified the types of open green space in the specified sampling points. These types represent the condition of the latest open green space model in the study area. Meanwhile, the secondary data consisted of spatial data, which can be observed in Table 1.  Since UAV-derived images have a high spatial resolution [31][32][33][34][35], they can describe the condition of an area in detail.
High-resolution satellite imagery is one of the advances in remote sensing technology. Satellite images depicting the conditions of the Earth's surface used to have a small spatial resolution, but now they provide spatial data with high resolution [36][37][38]

Open green Space Model in Yogyakarta City
Yogyakarta City is the center of development and economic activity in the Special Region of Yogyakarta. Infrastructure is the aspect with the most rapid growth in this city as it primarily aims to meet the persistently increasing public needs and economic activities. Such growth is characterized by the rising number of shopping centers and hotels. The direction of regional development is strongly related to the local spatial planning model, as well as the organization of open green space. This relationship leads to the diverse models of open green space in Yogyakarta City.
The sampling sites for identifying the open green space model in the study area is depicted in Figure 3. These sites were determined using purposive sampling technique.

The Distribution Pattern of Open green Space in Yogyakarta City
The method used to identify the distribution pattern of the Open green Space in Yogyakarta City was the Moran's Index. This index has been applied in various software. The data source used in the identification of the distribution pattern was the administrative boundaries of the villages in the city and the location of the Open green Space. The analysis results are presented in Figure 4. Because the process of inventory of open green spaces is still done in macro (general) has not done in detail. Such conditions cause the interpretation of the green space in the city of Yogyakarta is not evenly distributed, whereas the conditions in the field, there are various kinds of green space that may not have been inventory. Therefore, another method is needed for the inventory of open green space. One of them is use spatial data (spatial based).

Spatial-based Open green Space Inventory
Variety and types of existing data can be utilized for various purposes. One of them is spatial data that can be utilized for inventory of open green spaces. In this study, the application of spatial data utilization for open green space inventory is by using aerial photography data from Unmanned Aerial Vehicle (UAV). UAV is used copter type (quadcopter). The aerial photograph was taken at a sample location with a height of 350 ft, obtained 25 vertical photographs. Then in the next process is mosaic aerial photos. Mosaic photo results, can be observed in Figure 5. The result of the aerial photo mosaic process was obtained have a high spatial resolution level (4.23 cm). The data can be used for large-scale mapping. Further testing of accuracy by comparing laboratory accuracy to the field shows, the accuracy rate up to 92%. Inventory and identification of open green space based, spatial data can be applied with Landsat imagery data equipped with certain channels, but the resolution level of Landsat image data is still very small that is 30M and 15 M in sharpening process. Using the aerial photograph data with spatial resolution and high accuracy inventory and identification process will get accurate RTH data.
Identification of open green spaces and this distribution needs to be done, to support sustainable development goal. Benefits of open green space can be observed in Table 3 [39]. Based on the results of the analysis using moran's index, the pattern of open green space in Yogyakarta is still clustered, indicating that open green space has not spread evenly, and just attention to the aesthetic elements only. In some central locations of community activities, it is necessary to build open green space so that environmental balance can be maintained. The location data of open green space area in Yogyakarta city also need to be updated. The process of updating data and inventory of open green spaces, can utilize by spatial data of aerial photography from Unmanned Aerial Vehicle (UAV) because it has a high degree of resolution and accuracy.
Authors would like to thank the Indonesian Ministry of Research, Technology, and Higher Education for supporting this research. Authors would also like to thank colleagues that have been helpful during the study.