Effectiveness Of Cartogram For Representation Of Globeland30 Data

GlobeLand30, the world’s first global land cover dataset at 30m resolution for the years 2000 and 2010, was recently released and donated by China to the United Nations. GlobeLand30 refers to various material types on the earth’s surface. For publishing and sharing the GlobeLand 30 well, an effective type for visualization is urgently needed. There are many types for visualisation of the geographical distribution of spatial data. Evaluation of the effectiveness of visual variables for map presentation has been an important research topic in cartography. Cartogram is a powerful method for the visual representation of statistical data. Some researchers consider cartogram as a very effective technique for visualisation of spatial data, while others doubt about the effectiveness because of the possible distortion in shape and/or disconnectivity in topology.This study is aiming at evaluation the effectiveness of cartogram for visualizing the GlobeLand 30 data. The evaluation is consistented of two parts. One is the comparison between cartogram and thematic map and the other is the effect from map projections for GlobeLand 30 data visualisation. In the comparison between cartogram and thematic map ,Qualitative analysis method is used, the evaluation is made of effectiveness, efficiency. A clinic survey using a questionnaire is conducted for the evaluation. The questionnaire is placed on the Internet. In the effect from map projections, quantitative and qualitative analysis methods are adopted, the quantitative analysis is done at principle level and the qualitative analysis is made by comparing the differences between different projections from the perspective of perceiving recognition.The results of comparison between cartogram and thematic map shows that thematic map is better than cartogram on the expression of area while on the expression of tendency distribution and areas’multiple relationships, cartogram is better. These two methods have no significant difference in influence on efficiency. On the perspective of satisfaction, different testees are same as researchers that have different opinion on cartogram. The characters of cartogram are shortages to some people and advantages to other people. Areas’ irregular shape is the main factor that affects the effectiveness of cartogram. The results of quantitative analysis experiment of the influence of projection on cartogram show that equal-area projection has the smallest y value which means that equal-area projection effect cartogram less than other projections. And the results of qualitative analysis experiments show that the differences between different projections used in Cartogram can be recognized according to the latitude. In the cartogram for representation for GlobeLand 30 data,the projection will impact the effectiveness of cartogram in the high latitude while impact little in the low latitude.