The Quantitative Study Of The Legend Of Thematic Map

Thematic map is a kind of carrier of geographic information visualization, andmap users can make full use of geographic information accurately and rapidly by agood style of legend. The legend is an important part of the transfer of geographicinformation, which can explain the content and connotation of the symbols. Thematicmap plays an important role in all walks of life, and the function of legend isparticularly important.Due to the complexity of geographic entities and phenomena, the particularity ofsymbol, a lot of difficulties can be found in the process of the compilation of thematicmaps. Traditional thematic maps mostly need manual drafting and artificialpreparation. With the rapid development of computer technology and geographicinformation system, thematic map’s symbol and the design and compilation ofthematic map’s legend have got great improvement, but there are a lot of problems,such as a lower accuracy, higher error rate, lower standardization, lower automationand more time and effort consuming. So in order to achieve the accurate expression ofthematic map, the automation and standardization of legend is around the corner.Based on point, line, polygon symbols, this paper studied the quantitativeexpression of legend of thematic map by object-oriented theory, which could makelegend expression be more flexible, strengthen the understanding of the complicatedgeographical information and make drawing more standardization. The main contentsare as follows:1. According to different expression contents of thematic map, we can analyzethe composition of general legend: colors, symbols, annotations, names, grades and soon;2. According to national standards and related industry standard, we put forwardthe solution of the legend quantitative, including the quantitative of the number oflegend, legend symbols, legend annotations, legend names, legend order, legendlayout, legend classification and so on; 3. Dynamic legend which is based on spatial data is mainly carried the analysisfrom the design thought, function design, data processing design and so on. Andfinally we can realize the quantitative expression of dynamic legend based on spatialdata;4. The quantitative expression of static legend which is based on the interaction,taking the five aerogeophysical professional legend for example: profile, track line,abnormal point, contour and color ramp can be realized one by one;5. Legend module is encapsulated in the form of dynamic link library, which isuseful to do integration and invocation for other systems.Finally, we summarize the prospect and the problem existing in the quantitativeexpression of the legend of the thematic map.