Date Published: January 25, 2017
Publisher: Public Library of Science
Author(s): Nan Dong, Xiaohuan Yang, Hongyan Cai, Fengjiao Xu, Gui-Quan Sun.
The research on the grid size suitability is important to provide improvement in accuracies of gridded population distribution. It contributes to reveal the actual spatial distribution of population. However, currently little research has been done in this area. Many well-modeled gridded population dataset are basically built at a single grid scale. If the grid cell size is not appropriate, it will result in spatial information loss or data redundancy. Therefore, in order to capture the desired spatial variation of population within the area of interest, it is necessary to conduct research on grid size suitability. This study summarized three expressed levels to analyze grid size suitability, which include location expressed level, numeric information expressed level, and spatial relationship expressed level. This study elaborated the reasons for choosing the five indexes to explore expression suitability. These five indexes are consistency measure, shape index rate, standard deviation of population density, patches diversity index, and the average local variance. The suitable grid size was determined by constructing grid size-indicator value curves and suitable grid size scheme. Results revealed that the three expressed levels on 10m grid scale are satisfying. And the population distribution raster data with 10m grid size provide excellent accuracy without loss. The 10m grid size is recommended as the appropriate scale for generating a high-quality gridded population distribution in our study area. Based on this preliminary study, it indicates the five indexes are coordinated with each other and reasonable and effective to assess grid size suitability. We also suggest choosing these five indexes in three perspectives of expressed level to carry out the research on grid size suitability of gridded population distribution.
Grid cell is the basic unit to express population distribution information based on gridded population data. The choice of suitable grid size is very important, as the resolution must be fine enough to capture the desired spatial variation of population within the area of interest . Note that if the grid size exceeds the size of the smallest areal unit (i.e., block/parcel/residential building), data will be lost in the vector to raster transformation. In contrast, data redundancy will be generated if the grid size is less than the size of the areal unit when rasterizing vector data. Besides, there has scale dependency in the spatial distribution of population . And the characteristics of population distribution patterns are different at varied grid scales [3, 4]. Therefore, in order to reveal the actual spatial distribution of population, it is necessary to analyze characteristics of population distribution from different grid scales for a suitable grid size. The research on grid size suitability refers to determining an appropriate grid resolution to express the desired spatial variation of population distribution. It is significant to overcome effectively the limitations caused by unsuitable grid cell size or scale dependency.
The primary task of disaggregating census data to a regular grid is to determine grid size. How to choose a suitable grid size, which one can better express the spatial characteristics of population distribution, is important to improve the quality of spatialization of census data. Consequently, it is deserved to discuss how to select reasonable and effective indicators to assess grid size suitability. Combining with the existing work and the connotation of grid scale suitability, this study elaborated the reasons for choosing five indexes to analyze grid size suitability in terms of location expressed level, numeric information expressed level and spatial relationship expressed level.
In summary, this study summarized three expressed levels to analyze grid size suitability, which include location expressed level, numeric information expressed level, and spatial relationship expressed level. Five indexes were selected to explore expression suitability of population distribution on different grid scales. The five indexes are consistency measure (CM), shape index rate (SIR), standard deviation of population density (SDPD), patches diversity index (PDI), and the average local variance (ALV), respectively. The suitable grid size was determined by constructing grid size-indicator value curves and suitable grid size scheme. Finally, we presented the accuracy assessment about suitable grid size.