A novel cartography scheme based on run-length operation

Map exporting plays a crucial role in the realization of spatial data visualization. However, this process will be slow and high memory required when dealing with high precision map or enormous data. A fast cartography approach based on run length coding is proposed in this paper. The main idea is to express map symbol using run length set rather than dot matrix, thus the disposal of various form of symbol, linetype or label in cartography pattern can achieve through the operation of run length set, which will largely cut down redundant information emerged in the process of map rendering. The core of our scheme is geographical element expression with run-length set and run length overlay calculation of multiple layers, specifically to explore how map symbol and cartographic products are created by using run-length code. A detailed description about design of dot-form symbol is presented in this paper. We argue that dot-form symbol is a block of different size run-length segment, which records the complete color attribute. The design of complex symbol is built through the operation of fundamental run-length block, which have been implemented in previous research. In addition, other styles of map symbol can create in the same pattern. Based on this representation, it is actually plug in a block of run-length when insert a symbol into map layer. Thus, the map document can be taken as a set of run-length in different layers. While the map product is the final superposition effect of layers, combination of run-length block in each layer is necessary for the ultimate cartography pattern. The procedure is as follows: (1) progressive scan cartography space; (2) compare each layer with uppermost layer to determine merge or resolve run-length blocks to form ultimate run-length set, which is executed by adding operation of run-length for layers. The rules of disposing run-length block or not is discussed in detail. Thereby, all cartography features are contained in the final run-length set and map export will be realized in a short time for smaller memory space. The advantages of the scheme in speed and memory consumption are illustrated by comparative analysis with existing cartography system. Simultaneously, performance analysis concerning thematic map series is made at the end of this paper.