Bor-Wen Tsai

The Effect of DEM Resolution on Slope and Aspect Mapping

This article examines the effect of the spatial resolution of digital elevation models (DEMs) on slope and aspect data. After a review of computing methods for slope and aspect and such factors as DEM resolution, topographic complexity, and quality of DEM data, the article presents two experiments using DEMs from 8 to 80 m intervals. Results of the experiments show that the accuracy of slope and aspect data, as well as the mean and standard deviation of slope values, decrease with lower DEM resolutions. Comparison of slope and aspect maps generated from different resolutions reveals that slope differences concentrate in areas of steep slopes, whereas aspect differences are in generally flat areas with minor landform features. Slope differences can be explained statistically by relative relief, and aspect differences by relative relief and standard deviation of elevation.

Multi-layer multi-class dasymetric mapping to estimate population distribution.

The spatial patterns of population distribution are very important information for most regional planning and management decisions. But the socioeconomic data are usually published in areal aggregated format due to privacy concerns. Although choropleth maps are used extensively to display spatial distributions of these areal aggregated data, patterns may be distorted due to assumptions of homogeneous distributions and the modifiable areal unit problem. Most human activity, including population distribution, is spatially heterogeneous due to variations in topography and regional development. A multi-layer multi-class dasymetric (MLMCD) framework was proposed in this study to better redistribute the regionally aggregated population statistics into smaller areal units and reveal more realistic spatial population distribution pattern. The Taipei metropolitan area in Taiwan was used as a case study area to demonstrate the disaggregation ability of the proposed framework and the improvements to the traditional binary or multi-class dasymetric method. Assorted data, including remote sensing images, land use zoning, topography, transportation and accessibility to facilities were introduced in different layers to improve the redistribution of aggregated regional population data. The concept of multi-layer multi-class dasymetric modeling is both useful and flexible. Different levels of accuracy in this population redistribution process can be achieved depending on data and budget availabilities and the needs for different data usage purposes.

Analyzing Spatial and Temporal Changes of Aquaculture in Yunlin County, Taiwan∗

Abstract This article analyzes spatial and temporal changes of aquaculture land use in Yunlin County, Taiwan, and discusses the driving forces for these changes. Digital land-use maps and satellite imagery for 1982, 1988, 1994, and 2002 were used to extract aquaculture areas. A geographic information system was used to derive changes in aquaculture areas and to compute the spatial clustering statistics over time. A survey of eighty-seven farmers was conducted to obtain their views and concerns about aquaculture. The results show a rapid expansion in aquaculture during the 1980s, driven mainly by exports to Japan, and a continuous decline since the mid-1990s because of economic, environmental, and demographic factors.

The Spatial Knowledge of Indigenous People in Mountainous Environments: A Case Study of Three Taiwanese Indigenous Tribes

This article recounts information gleaned from a case study of three indigenous tribes in Taiwan regarding the origin and nature of their spatial knowledge. Sketched mental maps and 3D virtual environment () are used by indigenous elders and hunters to delineate their traditional territories. Spatial components representing the predominant spatial elements are identified. Spatial structures used for locational positioning are analyzed, as are spatial reference systems for orientation and movement. The results show that spatial components are used for daily activities, as well as having historical and cultural meaning; a quadrant structure is used for spatial positioning; and instead of using the directional reference system of east, south, west, and north, these indigenous people rely on the orientation analogies of uphill, downhill, upstream, and downstream for direction.

Teaching Topographic Map Skills and Geomorphology Concepts with Google Earth in a One-Computer Classroom.

Abstract Teaching high-school geomorphological concepts and topographic map reading entails many challenges. This research reports the applicability and effectiveness of Google Earth in teaching topographic map skills and geomorphological concepts, by a single teacher, in a one-computer classroom. Compared to learning via a conventional instructional method, students learning with Google Earth do not have different geomorphological concepts development because both settings enable students to learn with similar static representation. However, students learning with Google Earth improve topographic map skills significantly compared to the conventional instructional method. This is because of the 3D landscape visualization and prior knowledge connections available with Google Earth.

Use of PPGIS for Indigenous Mapping: An Assessment of Data and Function Needs

Public participation geographic information system (PPGIS) has been widely used in indigenous mapping recently. Much attention has been paid to participation and empowerment but little has been considered for system design. This research deals with system design, especially focusing on data provision, system functionality and the relationship between the two. What data are required and how data are presented are the major concerns of data provision. The results of this study show that GIS vector data, scanned map images and 3D virtual environment (digital elevation model overlaid with high resolution imagery) play important roles at different stages of the entire process of spatial cognition. Data browsing, query, measurement and visualization are commonly used GIS functions in indigenous mapping.

Fractal Formation of Settlement Forms in Taiwan

Fractal geometry has recently caught great attention in urban, ecology, and GIS research. This paper employs box-counting method to measure the settlement forms of twenty jurisdictions in Taiwan. The computed fractal dimensions are then linked to population density and ratio of urban area to total land area for each jurisdiction. The results are compared to Shens study (2002) to investigate the difference between the development of settlements in the U.S. and that in Taiwan. The conclusions are: 1) the fractal measures satisfies the inequality of 1＜D＜2 and can be regarded as proof of urban fractal that has been studied by several researchers, 2) the computed fractal measures coincides with the pattern of the spatial distribution of various settlements, that is, scattered in northern Taiwan, compact in the southern and the eastern regions, and 3) similar characteristics exist between settlements in Taiwan and cities in the US in terms of their spatial forms and population and urban area parameters.