Testing the Usability of Interactive Maps in CommonGIS

The paper reports on an experimental study aimed at assessing the usability of five different interactive tools for exploratory analysis of geographically referenced data implemented in CommonGIS. Usability was assessed in terms of tool learnability, memorability, and user satisfaction. The study provided valuable data concerning the usability of each individual tool; we also derived some conclusions relevant to geovisualization techniques in general. We found that users were, in principle, able to understand and adopt the new ideas of map interactivity and manipulability. However, these ideas needed to be appropriately introduced; people could hardly grasp them just from the appearance of the maps and controls. An introductory demonstration was sufficient to understand the purposes of the interactive tools, and a short training session enabled people to use them. The importance of educating users is a particular challenge for geovisualization tools that are intended to be accessed over the Internet.     

Towards Usability Engineering for Online Editors of Volunteered Geographic Information: A Perspective on Learnability

This article presents one of the first systematic usability investigations for a Volunteered Geographic Information (VGI) editor. This research is motivated by the fact that although VGI is now widely consumed, contribution rates are lagging considerably. Compared to traditional GIS interfaces, with complex interfaces resulting in high cognitive loads and barriers to participation, VGI tools and interfaces need to be easy to use and learn to encourage and facilitate contributions. This article develops a case study of OpenStreetMap, one of the most successful VGI projects, and its default editor, Potlatch2. Ten participants with no prior experience of VGI contribution, were instructed to contribute data to OSM in a structured exercise, while being monitored using an eye tracker and audio/video screen capture software. Each participant was asked to Think Aloud, i.e. describe what they were thinking and doing as they completed the tasks. The results highlight significant usability issues impacting learnability, especially from the perspective of a new contributor: hidden functionality, lack of user feedback between interactions and the inefficient and inconsistent placement of functionality and map controls. The facilitation of VGI contributions clearly depends on designing targeted interfaces, optimized to the needs of specific levels of contributors with defined goals and expectations.     

机载LiDAR安置角检校定标器设计与验证

传统的检校安置角误差的方法依靠人工量测重叠航带同名特征间的偏移来估计安置角误差,但是同名特征的真实位置难以获取,并且人眼瞄准误差的存在降低了检校精度。因此设计了一种定标器来解决同名特征的获取难题。首先介绍了定标器的结构特点和设计原理,然后制作了缩放模型并进行了半仿真地面扫描实验,分析了定标器的可用性。最后制作了实物进行飞行实验进一步证明其设计的合理性。研究结果表明定标器的设计是合理的。     

Usability Issues in Applying Participatory Mapping for Neighborhood Infrastructure Planning

Public participation is required in neighborhood infrastructure planning and problem‐solving. Although Participatory GIS methods are considered important to help urban community groups identify problems and express their needs and concerns, usable means to help groups produce their maps remain difficult to be realised. Further, an effective means to facilitate the integration of government spatial plans and participatory maps also remains unclear. This article addresses usability issues in participatory mapping activities by exploring group collaboration mechanics and accomplishing use assessments. The study aims at testing the usefulness and the impact of participatory mapping for community development. User studies including questionnaire surveys, interviews, group usability testing, scenario assessments, and the scaling‐up activity were executed. Transparent photomaps, Mobile GIS, and a Web map were implemented and assessed in the study area. A use scenario for community and official spatial data integration was also developed. The results of user studies show that the use of transparent photomaps is more effective to complete group tasks to discuss, draw, and annotate their infrastructure problems. For group participants, the transparent maps are more engaging, easy to learn, and more error tolerant than the use of Mobile GIS. A combination use of simple and advanced PGIS methods is necessary to be implemented to reach informed priority‐decision making.     

地学信息可视化系统的可用性辅助评估工具设计研究

针对传统可用性评估方法中存在的主要问题,提出要设计地学信息可视化系统的可用性辅助评估工具。本文首先分析传统常用的可用性评估方法及其存在的主要不足,提出解决这些问题的基本想法。然后提出地学信息可视化系统可用性辅助评估工具的总体设计思路及系统的工作流程,并详细阐述了系统的功能模块与关键技术实现。该工具可以减少测试过程中的主观影响,节省开支,更加有效地利用有限的样本,提高可用性评估结果的科学性。     

Legend Layouts for Thematic Maps: A Case Study Integrating Usability Metrics with the Thinking Aloud Method

Abstract

The legend is a critical tool in reading and interpreting a thematic map. The goal of the study reported here is to understand how the legend works as a map is read. The methodology combined usability performance metrics with the thinking aloud method. Subjects were asked to perform two sets of tasks using two thematic maps with different legend layouts. While latency and accuracy of answers for the first set of tasks did not differ significantly between users of the different layouts, users clearly preferred legends that were simple or familiar. The thinking aloud protocols from the second part of the study revealed different patterns of legend comprehension for each legend design. In addition, the study identified four problem-solving strategies that were adopted by the subjects. Finally, some principles for designing legends were developed from the results of the study.     

Using Eye-tracking and Mouse Metrics to Test Usability of Web Mapping Navigation

The growth of web-based mapping is transforming geovisualization. Use of web mapping has become ubiquitous throughout much of the world and has sparked greater public interest in GIS and mapping. Despite the rapid growth of web mapping, there has been relatively little study of the design and usability of web maps. Moreover, the design and function of popular web mapping programs are sometimes at odds with standard GIS and cartographic practices for even the simplest of functions such as zooming into a feature of interest. This study advances understanding of web mapping design via web usability testing based on mouse metrics and eye tracking technology to assess the utility of four different web map navigation schemes: pan zoom; double clicking; zoom by rectangle; and wheel zoom. We found significant differences among the various interfaces, with marked preference for the standard GIS approach of rectangle zoom, followed closely by wheel zoom. Far fewer users preferred the web mapping standard of pan zoom or click zoom. In addition to finding significant differences in usability among these approaches, this work illustrates the broader utility of usability testing and eye tracking technology for creating a better web mapping experience for users.     

How many samples are needed? An investigation of binary logistic regression for selective omission in a road network

ABSTRACT

Selective omission in a road network (or road selection) means to retain more important roads, and it is a necessary operator to transform a road network at a large scale to that at a smaller scale. This study discusses the use of the supervised learning approach to road selection, and investigates how many samples are needed for a good performance of road selection. More precisely, the binary logistic regression is employed and three road network data with different sizes and different target scales are involved for testing. The different percentages and numbers of strokes are randomly chosen for training a logistic regression model, which is further applied into the untrained strokes for validation. The performances of using the different sample sizes are mainly evaluated by an error rate estimate. Significance tests are also employed to investigate whether the use of different sample sizes shows statistically significant differences. The experimental results show that in most cases, the error rate estimate is around 0.1–0.2; more importantly, only a small number (e.g., 50–100) of training samples is needed, which indicates the usability of binary logistic regression for road selection.     

星座异构基准站网虚拟参考站数据生成方法

针对各地现有卫星导航定位基准站可用星座存在差异性的问题,提出了按星座分别生成虚拟参考站数据的方法。该方法通过修正接收机钟差影响,实现了多个参考站作为主参考站生成同一个站点的虚拟观测值,有效避免了单个主参考站星座兼容性的影响,可为流动站提供更多的可用卫星。试验针对部分基准站不兼容北斗卫星的情况,分别在开阔区域和房角区域测试了按星座组网前后流动站的定位性能。结果显示：更多基准站参与服务能够改善虚拟参考站数据质量;按星座组网后流动站的定位质量更优,尤其可以显著改善流动站在房角等有遮挡区域的可用性和定位质量。研究成果对于有效整合当前各类基准站数据资源、提升服务对星座的兼容性具有实用价值。     

Prototyping an artificial neural network for burned area mapping on a regional scale in Mediterranean areas using MODIS images

Each year thousands of ha of forest land are affected by forest fires in Southern European countries such as Spain. Burned area maps are a valuable instrument for designing prevention and recovery policies. Remote sensing has increasingly become the most widely used tool for this purpose on regional and global scales, where a large variety of techniques and data has been applied. This paper proposes a semiautomatic method for burned area mapping on a regional scale in Mediterranean areas (the Iberian Peninsula has been used as a study case). A Multi-layer Perceptron Network (MLPN) has been designed and applied to MODIS/Terra Surface Reflectance Daily L2G Global 500m SIN Grid multitemporal composite monthly images. The compositing criterion was based on maximum surface temperature. The research covered a six year period (2001–2006) from June to September, when most of the forest fires occur. The resulting burned area maps have been validated using official fire perimeters and compared with MODIS Collection 5 Burned Area Product (MCD45A1). The MLPN shown as an effective method, with a commission error of 29.1%, in the classification of the burned areas, while the omission error was of 14.9%. The results were compared with the MCD45A1 product, which had a slightly higher commission error (30.2%) and a considerably higher omission error (26.2%), indicating a high underestimation of the burned area.     

格网点电离层垂直改正误差分析及其改进算法研究

格网点电离层垂直改正误差（GIVE）是对格网点电离层垂直误差的估计,该值如估计过小则会影响系统完好性,如估计过大则会影响系统可用性,一般以一定概率的置信上限表示。提出了一种格网点电离层垂直改正误差的改进算法,该算法在保证一定风险概率的条件下使得估值更加接近真实值,提高了系统的可用性。实测数据分析表明：该算法实用有效。     

参考经验模态分解-独立分量分析及其在GPS多路径误差处理中的应用

多路径误差在绝大部分应用中,其测站间相关性很弱,不能通过差分观测得到有效削弱,成为高精度GPS动态变形监测中的主要误差源。针对GPS多路径误差的特点,结合具有良好多尺度分解能力的经验模式分解方法(EMD)和具有良好盲分离能力的独立分量分析(ICA)方法,提出带参考信号的EMD-ICA方法来削弱多路径效应的影响。应用实例的结果证明了该方法的有效性。     

Analyzing GNSS data in precise point positioning software

This work demonstrates that precise point positioning (PPP) can be used not only for positioning, but for a variety of other tasks, such as signal analysis. The fact that the observation model used for accurate error modeling has to take into consideration the several effects present in GPS signals, and that observations are undifferenced, makes PPP a powerful data analysis tool sensitive to a variety of parameters. The PPP application developed at the University of New Brunswick, which is called GAPS (GPS Analysis and Positioning Software), has been designed and built in order to take advantage of available precise products, resulting in a data analysis tool for determining parameters in addition to position, receiver clock error, and neutral atmosphere delay. These other estimated parameters include ionospheric delays, code biases, satellite clock errors, and code multipath among others. In all cases, the procedures were developed in order to be suitable for real-time as well as post-processing applications. One of the main accomplishments in the development described here is the use of very precise satellite products, coupled with a very complete observation error modeling to make possible a variety of analyses based on GPS data. In this paper, several procedures are described, their innovative aspects are pointed out, and their results are analyzed and compared with other sources. The procedures and software are readily adaptable for using data from other global navigation satellite systems.     

Arno Peters: The man and his map

Abstract

This paper shows an experiment with tactile maps designed for visually impaired persons. Tests were carried out on a tactile map produced with 3D printing and including a new type of tactile symbols, volumetric symbols (3D). These symbols are localized faster than conventional flat relief symbols, with the same error rate, an improvement in the use of these tactile devices. Moreover, following tests, differences were found between types of participants with blind participants generally carrying out the proposed tasks better than the rest of users.     

Evaluation of noise annotation lines: using noise to represent thematic uncertainty in maps

Noise annotation lines are a promising technique to visualize thematic uncertainty in maps. However, their potential has not yet been evaluated in user studies. In two experiments, we assessed the usability of this technique with respect to a different number of uncertainty levels as well as the influence of two design aspects of noise annotation lines: the grain and the width of the noise grid. We conducted a web-based study utilizing a qualitative comparison of 2 areas in 150 different maps. We recruited participants from Amazon Mechanical Turk with the majority being nonexperts with respect to the use of maps. Our findings suggest that for qualitative comparisons of “constant uncertainty” (i.e., constant uncertainty per area) in thematic maps, noise annotation lines can be used for up to six uncertainty levels. During comparison of four, six, and eight levels, the different designs of the technique yielded significantly different accuracies. We propose to use the “large noise width, coarse grain” design that was most successful. For “mixed uncertainty” (i.e., uncertainty is not constant per area) we observed a significant decrease in accuracy, but for four levels the technique can still be recommended. This article is a follow-up to our conference paper reporting on preliminary results of the first of the two experiments.     

A multistage collaborative 3D GIS to support public participation

This paper presents a collaborative 3D GIS to support public participation. Realizing that public-involved decision-making is often a multistage process, the proposed system is designed to provide coherent support for collaborations in the different stages. We differentiate ubiquitous participation and intensive participation and identify their suitable application stages. The proposed system, then, supports both of the two types of participation by providing synchronous and asynchronous collaboration functionalities. Applying the concept of Digital Earth, the proposed system also features a virtual globe-based user interface. Such an interface integrates a variety of data, functions, and services into a unified virtual environment which is delivered to both experts and public participants through the Internet. The system has been designed as a general software framework and can be tailored for specific projects. In this study, we demonstrate it using a scene modeling case and provide a preliminary evaluation toward its usability.     

拟准检定法及其在测量中的应用初探

经典最小二乘平差假定观测数据中不含有粗差,但随着现代测绘技术发展,数据采集的自动化程度越来越高,对数据采集过程进行人工干预较难实现,观测结果包含粗差在所难免。本文探讨利用拟准检定法进行粗差探测的原理、特点及优势,并通过模拟算例,验证了拟准检定法处理粗差的有效性。     

风云三号D星天基BDS实时定位性能分析

随着北斗三号卫星导航系统(BeiDou navigation satellite system-3, BDS-3)开始向全球提供导航服务,独立使用BDS为在轨运行的卫星提供全球覆盖、全时段的定位服务成为可能。结合风云三号D星(FengYun-3D, FY-3D)全球卫星导航系统掩星探测仪(global navigation satellite system occultation sounder, GNOS)的真实在轨数据对天基BDS的定位性能进行了详细的分析。首先,使用BDS真实广播星历计算了在不同轨道高度下的可见卫星数和定位精度因子（position dilution of precision, PDOP）,并结合精密星历分析了广播星历的轨道误差、时钟误差及空间信号测距误差(signal-in-space range error, SISRE)。仿真结果表明,在95%的置信水平下,从地面到2 000 km的轨道高度,BDS在全球范围内最小可见卫星数为6,最大PDOP小于5,星座可用性已经达到100%,全球平均可见卫星数BDS比GPS(global positioning syste...     

多镜头组合型全景相机两种成像模型的定位精度比较

根据多镜头组合型全景相机的严格成像机理,分析了广泛采用的全景理想成像模型系统误差的来源,推导出误差分布规律,并深入比较了严格成像模型和理想成像模型之间的差异.首先,分析了理想模型的单片物方定位误差和像方后方交会误差,理论公式表明其误差分布和物像间距及视角大小相关;其次,分析了全景立体像对的理想核线误差,并证明误差受像对间的旋转角和Z坐标影响.最后,分别采用室内、外数据对两种模型的空间后方交会、核线模型、光束法平差进行比较分析.试验结果表明,室外条件下由于物距接近于全景投影面、立体影像间旋转角较小等因素,两种模型的差异很小,且都达到了相当于1像素左右的测量精度;在狭窄的室内条件下,由于物距小、旋转角大等因素,严格模型在测量精度上明显优于理想模型.     

pRPL 2.0: Improving the Parallel Raster Processing Library

This article presents an improved p arallel R aster P rocessing L ibrary – pRPL version 2.0. Since the release of version 1.0, a series of modifications has been made in pRPL to improve its usability, flexibility, and performance. While retaining some of the key features of pRPL, the new version has gained several new features: (1) a new DataManager class has been added for integrated data management, and to facilitate data decomposition, assignment mapping, data distribution, Transition execution, and load‐balancing; (2) a GDAL‐based raster data I/O mechanism has been added to support various geospatial raster data formats, and provide centralized and pseudo parallel I/O modes; and (3) a static load‐balancing mode and a dynamic load‐balancing mode using the task‐farming technique are provided. A parallel zonal statistics tool and a parallel Cellular Automata model were developed to demonstrate the usability and performance of pRPL 2.0. The experiments using the California datasets showed that the performance altered when different pRPL options (i.e. load‐balancing mode, I/O mode and writer mode) were used for different algorithms, datasets, and varying numbers of processes.