Cognitive Semantic Analysis and Dynamic Generation of Cartographic Symbols

Location-based services (LBS) requires generating real-time personalized and dynamic cartographic symbols. In order to tackle this problem, this paper proposes a structural description model and a dynamic generation method of cartographic symbols based on cognitive analysis. Following the cognitive semantics principle of‘reality-cognition-symbol’, the description model elaborates the mapping mechanism between symbol graphics and symbol semantics, which uses symbol morphemes as atomic units and semantic structure as description framework. The generation method is composed of a context-free grammar model which uses rules to generate cartographic symbols on the basis of morphemes. Through the modelling of graphic morphemes, structural morphemes and rule-based generation system, a grammar compiler for dynamic generation of cartographic symbols is redesigned. Lastly, experiments of dynamic generation of cartographic symbols in different contexts and semantics are performed to verify the feasibility of the proposed method. Therefore, this study leads to a further understanding of cognition and structure principles of cartographic symbols, and also pushes forward dynamic generation of cartographic symbols for related industries and applications

The Syntax Model of Mobile Maps Generation

Using the method of formal language (FL), the syntax model of mobile map generation is studied. The syntax model is located in the level of logical calculus of map generation based on the analysis of its process. Combined the hierarchical and recursive characteristics of map representation, the simplest form of syntax structure is abstracted as carto-lexicons and syntax-rules. The classification system of carto-lexicons is established as well as the model of the spatial relation predicate system, and the map operation rules and rules of different levels of syntactic units are discussed. The compilation process and key techniques of the syntax model are discussed, and the feasibility of the model is verified through mobile maps generation experiment. The essence of the model is a kind of formal language grammar, which uses finite rules and lexicons to generate maps automatically, as well as a kind of high-level cartography interface of human-computer interactive

Geo-registration of Unprofessional and Weakly-related Image and Precision Evaluation

The 3D geo-spatial model built by unprofessional and weakly-related image is a significant source of geo-spatial information. The unprofessional and weakly-related image cannot be useful geo-spatial information until be geo-registered with accurate geo-spatial orientation and location. In this paper, we present an automatic geo-registration using the coordination acquired by real-time GPS module. We calculate 2D and 3D spatial transformation parameters based on the spatial similarity between the image location in the geo-spatial coordination system and in the 3D reconstruction coordination system. Because of the poor precision of GPS information and especially the unstability of elevation measurement, we use RANSAC algorithm to get rid of outliers. In the experiment, we compare the geo-registered image positions to their differential GPS coordinates. The errors of translation, rotation and scaling are evaluated quantitively and the causes of bad result are analyzed. The experiment demonstrates that this geo-registration method can get a precise result with enough images

A Visual Salience Model of Landmark Based on Virtual Geographical Experiments

In this paper,a visual salience model of landmark based on virtual geography experiments is proposed for landmark discrimination and salience calculation.Taking the calculation of salience model of city buildings as an example,visual factors of landmarks and their calculation are first analyzed,and then a virtual experiment environment is developed to incorporate eye tracking as well as controllable and computable visual factors.Furthermore,a quantitative model of the relationship between eye movement factors and visual salience of landmark is derived from empirical results.Based on the quantitative model,further experiment is designed to solve the equation of visual salience model of landmark by fitting experimental data,which describes the relationship between a visual salience of landmark and visual factors.The key to the proposed method is to use eye movement factors to represent a salience model in a virtual environment with controllable and computable visual factors,and then the salience model can be calculated through landmark cognition experiments and data analysis.This method can not only reduce the complexity of landmark research,but also overcome the difficulty of repeating the experiments,which makes it a unique advantage to solve problem that tackles interaction mechanism between human and environments such as landmark discrimination

The effects of raindrop impact and runoff detachment on hillslope soil erosion and soil aggregate loss in the Mollisol region of Northeast China

Soil aggregates profoundly influence soil fertility and soil erosion. A large number of studies have showed that soil aggregate loss was mainly affected by raindrop impact and runoff detachment during hillslope erosion process; however, few attempts have been made to investigate which one plays the dominant role in soil aggregate loss. Therefore, a laboratory study was conducted to quantify the effects of raindrop impact and runoff detachment on soil erosion and soil aggregate loss during hillslope erosion processes. A soil pan (8 m long, 1.5 m wide, and 0.6 m deep and with an adjustable slope gradient of 0&ndash;35 ) was subjected to rainfall simulation experiments under two soil surface conditions: with and without raindrop impact through placing nylon net over soil pan. Two rainfall intensities (50 and 100 mm h 1) of representative erosive rainfall and two slope gradients (5 and 10 ) in the Mollisol region of Northeast China were subjected to two soil surface conditions. The results showed that raindrop impact played the dominant role in hillslope soil erosion and soil aggregate loss. Soil loss caused by raindrop impact was 3.6&ndash;19.8 times higher than that caused by runoff detachment. The contributions of raindrop impact to hillslope soil erosion were 78.3% to 95.2%. As rainfall intensity and slope gradient increased, soil loss caused by raindrop impact and runoff detachment both increased. The loss of each size aggregate was greatly reduced by 46.6&ndash;99.4% after eliminating raindrop impact. Meanwhile, the contributions of raindrop impact to the &gt;2, 1&ndash;2, 0.5&ndash;1, 0.25&ndash;0.5 and &lt;0.25 mm soil aggregate loss were 79.1% to 89.7%. Eliminating raindrop impact reduced rainfall intensity effect and increased slope gradient impact on aggregate loss.</div

Effectiveness of Rectangular Cartogram for Conveying Quantitative Information: An Eye Tracking-Based Evaluation

A rectangular cartogram is a kind of graphical representation that uses a rectangular area to represent the attributes of geographical objects and is widely used in the representation of statistical data such as population, economic statistics, and epidemic distribution. However, there is currently little research on the effectiveness of rectangular cartograms for conveying quantitative data. In this paper, the rectangular cartogram and unclassed choropleth map are compared to evaluate the rectangular cartogram’s effectiveness in quantity representation through task-driven eye-tracking cognitive experiments. In addition, the accuracy and efficiency of information communication and the differences in the reading processes of map readers when using the two types of maps for different tasks have been analyzed to provide references for more effective use of rectangular cartograms in the future. The main contributions of this paper are: (1) it has been proven by experiments that when completing the four tasks of locate, compare, find extreme, and estimate, the participants have higher accuracy rates with the rectangular cartogram; (2) the reading process shown by the eye tracking experiment shows that the more complex the task is, the more patient the participants would be with the rectangular cartogram, and the more pronounced the advantages of the rectangular cartogram are

Comparison of runoff and soil loss in different tillage systems in the Mollisol region of Northeast China

Longitudinal ridge tillage is the conventional tillage method in the cold, Mollisol region of Northeast China in which furrows are oriented up and down the slope. In part due to the use of this tillage system with large slope lengths, soil erosion is a serious problem in this region. Currently, it is unclear what the best tillage system and ridge orientation is for sustainable agriculture in this region. Thus to compare the runoff and soil loss in longitudinal (LRS) and contour ridge (CRS) systems to a flat tillage system (FTS), a series of simulated rainfall experiments were conducted. A large soil pan (8 m-long, 1.5 m-wide, and 0.6 m-deep) and a side sprinkler rainfall simulation system were used in this study with the three tillage systems (LRS, CRS, FTS) under three rainfall intensities (50, 75 and 100 mm h(-1)) at a 5 slope gradient. The results showed that runoff and soil loss in the LRS were larger than those in the CRS and FTS due to a shift in erosion pattern from sheet to concentrated flow erosion along furrows which led to shear stress increases. Contour ridge failures occurred in the 75 and 100 mm h-1 treatments by breaching of ridges when water stored in furrows exceeded their storage capacity. Breaching changed the runoff and soil loss by providing a large sediment source to the convergent flow. Water storage of CRS furrows was constant as rainfall intensity varied which led to overtopping during large storm conditions. Shifting conventional LRS to CRS with modifications to retain more rainwater during low to moderate rainfall events is highly recommended as this would reduce soil loss and enhance infiltration. The FTS exhibited the lowest runoff and soil loss which is recommended for the Mollisol region of Northeast China in large storm conditions