Value-by-alpha Maps: An Alternative Technique to the Cartogram

Abstract

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The cartogram, or value-by-area map, is a popular technique for cartographically representing social data. Such maps visually equalize a basemap before mapping a social variable by adjusting the size of each enumeration unit by a second, related variable. However, to scale the basemap units according to an equalizing variable, cartograms must distort the shape and/or topology of the original geography. Such compromises reduce the effectiveness of the visualisation for elemental and general map-reading tasks. Here we describe a new kind of representation, termed a value-by-alpha map, which visually equalizes the basemap by adjusting the alpha channel, rather than the size, of each enumeration unit. Although not without its own limitations, the value-by-alpha map is able to circumvent the compromise inherent to the cartogram form, perfectly equalizing the basemap while preserving both shape and topology.     

Design and evaluation of a geovisual analytics system for uncovering patterns in spatio-temporal event data

ABSTRACT

It remains difficult to develop a clear understanding of geo-located events and their relationships to one another, particularly when it comes to identifying patterns of events in less-structured textual sources, such as news feeds and social media streams. Here we present a geovisualization tool that can leverage computational methods, such as T-pattern analysis, for extracting patterns of interest from event data streams. Our system, STempo, includes coordinated-view geovisualization components designed to support visual exploration and analysis of event data, and patterns extracted from those data, in terms of time, geography, and content. Through a user evaluation, we explore the usability and utility of STempo for understanding patterns of recent political, social, economic, and military events in Syria.     

Visual clutter reduction in zoomable proportional point symbol maps

ABSTRACT

Proportional point symbols are commonly used in map displays. However, when such displays are zoomed out, the available map space shrinks and consequently symbols overlap and the display suffers from visual clutter. Therefore, solutions are needed to reduce visual clutter in zoomable map displays that contain proportional point symbols. The authors add to the body of knowledge through the investigation of the performance of three solutions: aggregation of unit areas, the displacement of overlapping symbols, and modified symbolization; four variations of modified symbolization are examined in detail. The original study begins with a consideration of the strengths and weaknesses of the solutions, with an emphasis on information loss. Thereafter, user sessions with 165 participants are arranged to gain empirical evidence of the performance of the solutions. The results reveal that although participants zoom out the map to zoom levels that implement visual clutter reduction techniques, they tend to zoom in the map and pan it to examine specific areas. Moreover, they willingly use the map with aggregated unit areas in cases when the solution facilitates task accomplishment. A certain amount of skepticism attaches to the solution that displaces overlapping symbols.     

Contemporary American cartographic research: a review and prospective

ABSTRACT

We review recent developments in cartographic research in North America, in the context of informing the 29th International Cartographic Conference, and 18th General Assembly in 2019. The titles of papers published since 2015 in four leading cartographic journals yielded a corpus of 245 documents containing 1109 unique terms. These terms were analyzed using Latent Dirichlet Allocation and by visual analytics to produce 14 topic groups that mapped onto five classes. These classes were named as information visualization, cartographic data, spatial analysis and applications, methods and models, and GIScience. The classes were then used as themes to discuss the recent cartographic literature more broadly, first, to review recent trends in the research and to identify research gaps, and second, to examine prospects for new research over the next 20 years. A conclusion draws some broad findings from the review, suggesting that cartographic research in the future will be aimed less at dealing with data, and more at generating insight and knowledge to better inform society about global challenges.     

城市公益性专题地图编制技巧

以武汉市公益地图编制为例,结合多年来专题地图编制经验和市场调研情况,总结出一套行之有效的城市公益性专题地图编制技巧,具有一定的参考价值。     

Exploratory analysis of the interrelations between co-located boolean spatial features using network graphs

Visual data mining of spatial data is a challenging task. As exploratory analysis is fundamental, it is beneficial to explore the data using different potential visualisations. In this article, we propose and analyse network graphs as a useful visualisation tool to mine spatial data. Due to their ability to represent complex systems of relationships in a visually insightful and intuitive way, network graphs offer a rich structure that has been recognised in many fields as a powerful visual representation. However, they have not been sufficiently exploited in spatial data mining, where they have principally been used on data that come with an explicit pre-specified network graph structure. This research presents a methodology with which to infer relationship network graphs for large collections of boolean spatial features. The methodology consists of four principal stages: (1) define a co-location model, (2) select the type of co-association of interest, (3) compute statistical diagnostics for these co-associations and (4) construct and visualise a network graph of the statistic from step (3). We illustrate the potential usefulness of the methodology using an example taken from an ecological setting. Specifically, we use network graphs to understand and analyse the potential interactions between potential vector and reservoir species that enable the propagation of leishmaniasis, a disease transmitted by the bite of sandflies.     

Weak numerical comparability of ISO-7027-compliant nephelometers. Ramifications for turbidity measurement applications

Nephelometric turbidity, a measure of light scattering by particles suspended in water, is commonly used for indicating water clarity or suspended particulate matter (SPM) concentration. Different turbidity sensors have long been known to respond differently to the same suspensions. Design standards have been introduced to improve comparability of turbidity sensors, notably the ISO-7027 standard adopted by a number of manufacturers. We compared six ISO-7027-compliant nephelometers in river silt, kaolinite (layer clay) and algae-laden pond water, with rigorous tank experiments over a wide (100-fold) concentration range. The responses of four different field-type (in situ) and two cuvette instruments, all calibrated to the same freshly made formazin standards, were very strongly linearly correlated, but ranged about twofold in magnitude. Apparently, even sensors meeting the same design standard (ISO-7027) cannot be relied on to output numerically similar formazin nephelometric unit (FNU) values. This weak numerical comparability highlights the futility of treating turbidity as an absolute quantity, for example in environmental standards or studies of fine SPM effects on aquatic life. Indeed, reporting of turbidity in informal units such as FNU is best avoided. Turbidity records should be converted, by site-specific calibrations, to quantities of ultimate interest such as SPM concentration or total phosphorus. For performance monitoring of field nephelometers, we advocate routine site-specific calibration, not to formazin, but to the light beam attenuation coefficient (beam-c; units: m⁻¹). Beam-c is a proper (SI) physical quantity that can be precisely measured by beam transmissometry, as in our experiments, and is accurately convertible to visual clarity.     

Producing global awareness? An analysis of Norwegian pupils’ negotiations of images in a museum exhibition

ABSTRACT

The article focuses on Norwegian pupils’ negotiations of meaning in images of social inequality in A World at Stake, a circulating museum exhibition in Denmark, Norway and Sweden that addressed the United Nation’s Millennium Development Goals. More specifically, the article focuses on the pupils’ engagement with two images in the exhibition. By investigating how the pupils negotiated the meaning of those images, the authors demonstrate some of the ways in which the pupils’ reported engagement and responses had the potential to foster critical debate relating to the North–South divide in terms of poverty and affluence. Drawing on critical visual methodology, the authors discuss their findings of how the pupils used their experiences to make sense of the images, situate their social identities within a globally and socially unjust world, and, by implication, the potential for two images to inspire them to reflect on their roles and responsibilities in the wider world. The authors conclude that although the pupils’ social identities to varying degrees were mobilized, AWAS spurred engagement and reflections that helped the authors to understand how the pupils saw themselves, their roles and their responsibilities beyond the Global North.     

浅析野外金的快速分析方法

该文选择野外快速测金的2种方法:氢醌容量法和目视比色法,从原理、试样分析、富集方法、吸附机理、解脱方式、试剂及分析手续几方面进行对比分析,着重对氢醌容量法作研究和完善工作。针对通过比对实验,确立分析测试条件,选择确定了快速、简便、经济的测试流程,并应用于样品测试,提高了检测速度。     

Edward Schenfeld: Visual photometry of variables: I. Comparison stars

Based on the SIMBAD database, we collected necessary information on the comparison stars used by E. Schenfeld in observations of variable stars in the 19th century.