ارزيابي كمي توزيع فضايي كاربري اراضي با استفاده از تابع Ripley’s K در شهر بجنورد

Quantitative evaluation of spatial distribution of land use in Bojnord Using Ripley’s K function

با توجه به ارزش ديدگاه فضايي در برنامه ­ريزي­ها، شناخت و تحليل روند تغييرات و نحوه­ ي توزيع كاربري­ها در سطح شهرها، تابع ريپلي مي­تواند به عنوان ابزاري كارآمد در جهت بررسي نحوه­ ي توسعه­ ي فضايي به كار آيد. ابزاري كه در حوزه­ي برنامه ­ريزي شهري و منطقه­ اي به كار نيامده است. در اين پژوهش كه از نظر ماهوي، كاربردي و از نظر روش، تحليلي – توصيفي است، با بهره ­گيري از تابع ريپلي، روند توسعه و توزيع فضايي كاربري­ها در سطح شهر بجنورد مورد بررسي قرار گرفته است. بجنورد در دهه ­ي 1380 به دليل ارتقا به مركزيت استان، رشدي سريع و ناگهاني در جمعيت و مساحت را تجربه كرده و به نوعي تعادل فضايي خود را از دست داده است. در ادامه به منظور آزمون درستي نتايج به دست آمده، از ضريب جهاني موران نيز بهره گرفته شد. به اين منظور نقشه­ هاي پايه و داده­هاي مورد نياز (كه از راه مطالعات اسنادي و نيز مشاهده جمع آوري گرديده است) توسط ابزارهاي موجود در نرم­افزار ArcGIS تجزيه و تحليل شده و خروجي­هاي لازم به دست آمد. نتيجه نشان مي­دهد كه توسعه­ ي فضايي و توزيع كاربري­ها در بجنورد نزديك به حالت متمركز بوده و در بخش­هاي حاشيه ­اي آن، حالتي تصادفي و بي­قاعده دارد. هم­خواني نتايج حاصل از تابع ريپلي و ضريب جهاني موران در اين پژوهش حكايت از آن دارد كه تابع k ريپلي مي­تواند ابزاري كارآمد در زمينه ­­ي سنجش نحوه­ ي توزيع فضايي كاربري­هاي شهري باشد.

Missing spatial approach in urban planning is one of the most important weaknesses which have been observed in urban settlements of Iran. Using quantitative methods in analyzing spatial distribution of urban land uses have been considered increasingly in recent years, which have been used and experienced throughout the world. Ripley’s K function is a statistical method which examines and estimates the spatial distribution pattern of geographical features in specified area. Here in this article the first time this function is applied to evaluate and analyze trend of spatial development in Bojnord especially the form and quality of land use distribution. Methodologically this can be considered as an applied research which uses descriptive and analytical methods to achieve its goal. So, required data have been collected through studying formal documents, surveying existent planes and analyzing maps and other visual references to derive needed information. In ArcGIS the Multi-Distance Spatial Cluster Analysis (Ripley's K-function) tool determines whether a feature class is clustered at multiple different distances. Bojnord with about 200,000 populations (2011) in the recent years has experienced a rapid and sudden growth in population and space. These changes lead to some problems in the urban area such as rising informal settlements around the city, wasting natural sources and lands and result in reduction of quality of life. In this study, the urban area divided into 26 separated zones which cover all over the city. These zones conform to the districts of municipality administration. The results show that beside the population, other observed data such as urban land uses (residential, cultural, green space etc.) have no determined pattern and generally can be considered as random distribution. To prove the results of Ripley’s K function in Bojnord and examine the efficiency of this index, the Moran’s global coefficient also has applied to the same data. This method shows same results. Population in Bojnord is generally clustered especially in center of the city. Other observed data have no specific pattern and randomly distributed in the urban area. It is shown that the results of two method match with each other. So Ripley’s K function can certainly be used to evaluate spatial distribution of geographical features and it can be considered as a quantitative method in urban and regional planning and spatial development.