Document Type : Research Paper

Authors

1 Ph.D. Student in remote sensing, Faculty of geodesy and geomatics engineering, K.N Toosi University of Technology, Tehran, Iran

2 Ph.D. in remote sensing, Iranian Space Research Center

3 Professor, Photogrammetry and remote sensing department, Faculty of geodesy and geomatics engineering, K.N Toosi University of Technology, Tehran, Iran

Abstract

Extended Abstract
1- Introduction
Remote Sensing (RS), as one of the most efficient mapping technologies, is employed in wide areas due to its speed, cost-effectiveness, monitoring over wide areas and using time series data. So far, several data and methods are used for this purpose. In general, RS active and passive sensors provide useful information in various applications such as building extraction, natural resource management, agricultural monitoring, etc. The extraction of accurate information about the location, density and distribution of buildings in the urban areas is one of the major challenges in the urban study which is used in various applications. In this framework, the monitoring of the urban parameters, such as urban green space, public health, and environmental justice, urban density and so on has been accomplished by radar and optical image processing, in the last three decades. So far, various methods, including Artificial Intelligence (AI), Deep Learning (DL), object-based methods, etc. have been proposed to extract information in the urban areas. However, an important issue is access to the powerful computer hardware to process the time-series images. In such a situation, the use of the Google Earth Engine (GEE) as a web-based RS platform and its ability to perform spatial and temporal aggregations on a set of satellite images has been considered by many researchers. In this research, a semi-automatic method was developed building extraction in Tabriz, northwest of Iran, based on the satellite images using the GEE cloud computing platform. Since accessible data is one of the most important challenges in the use of space RS, in this study, the free Sentinel-1 and sentinel-2 data, which belongs to the European Space Agency (ESA), has been utilized.
 
2- Materials & Methods
2-1- Study Area
The study area is central part of the city of Tabriz East Azerbaijan Province, which is located in northwestern of Iran.
 
2-2- Data
Various data sources have been used in this study, including Sentinel-1, Sentinel-2, and the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM). In addition, 400 training samples were created using High-Resolution Google Earth Imagery (GEI) in two classes: urban-residential (buildings) and non-residential areas (vegetation, soil, road, water and etc.).
2-3- Methodology
The goal of this research is to develop a method for identifying the buildings in an urban area. For this purpose, after importing images and pre-processing them in the GEE Platform, a map of the Primary Urban Areas (PUA) and High-Potential Buildings (HPB) was produced from Sentinel-1 images according to the sensitivity of the radar images to the target physical parameters. Then, in order to remove the annoying features and extract the Secondary Urban Areas (SUA), spectral indices such as Normalized Difference Vegetation Index (NDVI), Green Normalized Difference Vegetation Index (GNDVI), Renormalized Difference Vegetation Index (RDVI), Normalized Difference Water Index (NDWI), Soil Extraction Index (SOEI), Normalized Difference Built-up Index (NDBI), and Build-up Extraction Index (BUEI) were extracted from Sentinel-2 images. Also, the high slope of the area and the mountainous areas was extracted from the SRTM DEM data and used as a mask in the final results. Afterwards, the unimodal histogram thresholding method was used in order to determine the threshold value for each index. Finally, by merging the map of HPB and the map of SUA, the final map was produced and evaluated by other methods. In this research, the proposed method used images from GEI with a very high spatial resolution to validate the generated map. As a result, sampling was carried out using a visual interpretation of GEI in two classes: residential areas (buildings) and non-residential areas. The samples were selected randomly and 400 points were collected for each residential and non-residential class. In the study area, a total of 800 test points were used to evaluate the results of the proposed method. To evaluate the accuracy of the results, the criteria of overall accuracy (OA), kappa coefficient (KC), user accuracy (UA) and producer accuracy (PA) were used.
 
3- Results & Discussion
According to the visual interpretation, all buildings in urban areas with a length and width greater than 10 meters (spatial resolution of the four major bands of Sentinel2) can be extracted using the proposed method in this study, and the results are acceptable in various features. According to the proposed method, annoying features such as vegetation and water body areas were removed from the building identification process with high accuracy, and the accuracy in the study area was improved. The results showed that the OA and KC were 90.11 % and 0.803, respectively. Based on the quantitative and qualitative comparisons, the proposed method had a very satisfying performance.
 
4- Conclusion
Due to the spectral diversity and the presence of various features in urban environments, preparing a map related to it in a large area is extremely difficult. In this regard, the current study presented a very fast semi-automatic method for preparing the urban area map and extracting buildings in Tabriz using Sentinel-1 and Sentinel-2 satellite images as a time series in the GEE platform. One of the most significant benefits of the proposed method is that the data and processing system used in our study is free. Thus, in addition to not having to download large amounts of data, the method presented in the current study has the ability to eliminate many of the limitations of traditional methods, such as classification methods and their requirement for large training samples. The proposed method did not extract the map of buildings using heavy and complex algorithms, which was an important consideration in the discussion of computational cost. Therefore, it can be concluded that the simultaneous use of Radar and optical RS data in the GEE Web-Based platform has a very high potential in distinguishing features and building mapping.

Keywords

1- Arnold Jr, C. L., & Gibbons, C. J. (1996). Impervious surface coverage: the emergence of a key environmental indicator. Journal of the American planning Association, 62(2), 243-258.
2- Ban, Y., Jacob, A., & Gamba, P. (2015). Spaceborne SAR data for global urban mapping at 30 m resolution using a robust urban extractor. ISPRS Journal of Photogrammetry and Remote Sensing, 103, 28-37.
3- Bouziani, M., Goïta, K., & He, D.-C. (2010). Automatic change detection of buildings in urban environment from very high spatial resolution images using existing geodatabase and prior knowledge. ISPRS Journal of Photogrammetry and Remote Sensing, 65(1), 143-153.
4- Bramhe, V., Ghosh, S., & Garg, P. (2018). Extraction of Built-up areas using Convolutional Neural Networks and transfer learning from Sentinel-2 Satellite Images. International Archives of the Photogrammetry, Remote Sensing & Spatial Information Sciences, 42(3).
5- Chen, J., Chen, J., Liao, A., Cao, X., Chen, L., Chen, X., He, C., Han, G., Peng, S., & Lu, M. (2015). Global land cover mapping at 30 m resolution: A POK-based operational approach. ISPRS Journal of Photogrammetry and Remote Sensing, 103, 7-27.
6- Civco, D. L., Hurd, J. D., Wilson, E. H., Arnold, C. L., & Prisloe Jr, M. P. (2002). Quantifying and describing urbanizing landscapes in the Northeast United States. Photogrammetric engineering and remote sensing, 68(10).
7- Deng, C., & Wu, C. (2012). BCI: A biophysical composition index for remote sensing of urban environments. Remote Sensing of Environment, 127, 247-259.
8- Feyisa, G. L., Meilby, H., Jenerette, G. D., & Pauliet, S. (2016). Locally optimized separability enhancement indices for urban land cover mapping: Exploring thermal environmental consequences of rapid urbanization in Addis Ababa, Ethiopia. Remote Sensing of Environment, 175, 14-31.
9- Forget, Y., Linard, C., & Gilbert, M. (2017). Automated supervised classification of Ouagadougou built-up areas in Landsat scenes using OpenStreetMap. Paper presented at the 2017 Joint Urban Remote Sensing Event (JURSE).
10- Ghorbanian, A., Kakooei, M., Amani, M., Mahdavi, S., Mohammadzadeh, A., & Hasanlou, M. (2020). Improved land cover map of Iran using Sentinel imagery within Google Earth Engine and a novel automatic workflow for land cover classification using migrated training samples. ISPRS Journal of Photogrammetry and Remote Sensing, 167, 276-288.
11- Gitelson, A. A., Kaufman, Y. J., & Merzlyak, M. N. (1996). Use of a green channel in remote sensing of global vegetation from EOS-MODIS. Remote Sensing of Environment, 58(3), 289-298.
12- Goward, S. N., Markham, B., Dye, D. G., Dulaney, W., & Yang, J. (1991). Normalized difference vegetation index measurements from the Advanced Very High Resolution Radiometer. Remote Sensing of Environment, 35(2-3), 257-277.
13- Hansen, M. C., & Loveland, T. R. (2012). A review of large area monitoring of land cover change using Landsat data. Remote Sensing of Environment, 122, 66-74.
14- He, C., Shi, P., Xie, D., & Zhao, Y. (2010). Improving the normalized difference built-up index to map urban built-up areas using a semiautomatic segmentation approach. Remote Sensing Letters, 1(4), 213-221.
15- Hegazy, I. R., & Kaloop, M. R. (2015). Monitoring urban growth and land use change detection with GIS and remote sensing techniques in Daqahlia governorate Egypt. International Journal of Sustainable Built Environment, 4(1), 117-124.
16- Huang, H., Chen, Y., Clinton, N., Wang, J., Wang, X., Liu, C., Gong, P., Yang, J., Bai, Y., & Zheng, Y. (2017). Mapping major land cover dynamics in Beijing using all Landsat images in Google Earth Engine. Remote Sensing of Environment, 202, 166-176.
17- Jensen, J. R. (1996). Introductory digital image processing: a remote sensing perspective: Prentice-Hall Inc.
18- Li, G., Lu, D., Moran, E., & Hetrick, S. (2013). Mapping impervious surface area in the Brazilian Amazon using Landsat Imagery. GIScience & remote sensing, 50(2), 172-183.
19- Li, L., Zhou, H., Wen, Q., Chen, T., Guan, F., Ren, B., Yu, H., & Wang, Z. (2018). Automatic Extraction of urban Built-up area based on object-oriented method and remote sensing data. International Archives of the Photogrammetry, Remote Sensing & Spatial Information Sciences, 42(3).
20- Liu, C., Shao, Z., Chen, M., & Luo, H. (2013). MNDISI: a multi-source composition index for impervious surface area estimation at the individual city scale. Remote Sensing Letters, 4(8), 803-812.
21- Liu, D., Chen, N., Zhang, X., Wang, C., & Du, W. (2020). Annual large-scale urban land mapping based on Landsat time series in Google Earth Engine and OpenStreetMap data: A case study in the middle Yangtze River basin. ISPRS Journal of Photogrammetry and Remote Sensing, 159, 337-351.
22- McFeeters, S. K. (1996). The use of the Normalized Difference Water Index (NDWI) in the delineation of open water features. International journal of remote sensing, 17(7), 1425-1432.
23- Ndehedehe, C. E., Oludiji, S. M., & Asuquo, I. (2013). Supervised learning methods in the mapping of built up areas from Landsat-based satellite imagery in part of Uyo Metropolis. New York Science Journal, 6(9), 45-52.
24- Rawat, J., & Kumar, M. (2015). Monitoring land use/cover change using remote sensing and GIS techniques: A case study of Hawalbagh block, district Almora, Uttarakhand, India. The Egyptian Journal of Remote Sensing and Space Science, 18(1), 77-84.
25- Rosin, P. L. (2001). Unimodal thresholding. Pattern recognition, 34(11), 2083-2096.
26- Spence, M., Annez, P. C., & Buckley, R. M. (2008). Urbanization and growth: World Bank Publications.
27- Sun, Z., Guo, H., Li, X., Lu, L., & Du, X. (2011). Estimating urban impervious surfaces from Landsat-5 TM imagery using multilayer perceptron neural network and support vector machine. Journal of Applied Remote Sensing, 5(1), 053501.
28- Sun, Z., Xu, R., Du, W., Wang, L., & Lu, D. (2019). High-resolution urban land mapping in China from sentinel 1A/2 imagery based on Google Earth Engine. Remote Sensing, 11(7), 752.
29- Teo, T.-A., & Shih, T.-Y. (2013). Lidar-based change detection and change-type determination in urban areas. International journal of remote sensing, 34(3), 968-981.
30- Valdiviezo-N, J. C., Téllez-Quiñones, A., Salazar-Garibay, A., & López-Caloca, A. A. (2018). Built-up index methods and their applications for urban extraction from Sentinel 2A satellite data: discussion. JOSA A, 35(1), 35-44.
31- Vigneshwaran, S., & Kumar, S. V. (2018). Extraction of Built-up area using Highresolution Sentinel-2A and Google Satellite Imagery. International Archives of the Photogrammetry, Remote Sensing & Spatial Information Sciences, 42.
32- Wang, Z., Gang, C., Li, X., Chen, Y., & Li, J. (2015). Application of a normalized difference impervious index (NDII) to extract urban impervious surface features based on Landsat TM images. International journal of remote sensing, 36(4), 1055-1069.
33- Xian, G., & Homer, C. (2010). Updating the 2001 National Land Cover Database impervious surface products to 2006 using Landsat imagery change detection methods. Remote Sensing of Environment, 114(8), 1676-1686.
34- Xu, H. (2007). Extraction of urban built-up land features from Landsat imagery using a thematicoriented index combination technique. Photogrammetric Engineering & Remote Sensing, 73(12), 1381-1391.
35- Yang, L., Huang, C., Homer, C. G., Wylie, B. K., & Coan, M. J. (2003). An approach for mapping large-area impervious surfaces: synergistic use of Landsat-7 ETM+ and high spatial resolution imagery. Canadian journal of remote sensing, 29(2), 230-240.
36- Zha, Y., Gao, J., & Ni, S. (2003). Use of normalized difference built-up index in automatically mapping urban areas from TM imagery. International journal of remote sensing, 24(3), 583-594.
37- Zhang, C., Sargent, I., Pan, X., Li, H., Gardiner, A., Hare, J., & Atkinson, P. M. (2018). An object-based convolutional neural network (OCNN) for urban land use classification. Remote Sensing of Environment, 216, 57-70.
38- Zhang, J., Li, P., & Wang, J. (2014). Urban built-up area extraction from Landsat TM/ETM+ images using spectral information and multivariate texture. Remote Sensing, 6(8), 7339-7359.
39- Zhang, X., Liu, L., Wu, C., Chen, X., Gao, Y., Xie, S., & Zhang, B. (2020). Development of a global 30 m impervious surface map using multisource and multitemporal remote sensing datasets with the Google Earth Engine platform. Earth System Science Data, 12(3), 1625-1648.
40- Zhao, D., Li, J., & Qi, J. (2005). Identification of red and NIR spectral regions and vegetative indices for discrimination of cotton nitrogen stress and growth stage. Computers and Electronics in Agriculture, 48(2), 155-169.