Existing literature about online handwriting analysis to support pathology diagnosis has taken advantage of in-air trajectories. A similar situation occurred in biometric security applications where the goal is to identify or verify an individual using his signature or handwriting. These studies do not consider the distance of the pen tip to the writing surface. This is due to the fact that current acquisition devices do not provide height formation. However, it is quite straightforward to differentiate movements at two different heights (a) short distance: height lower or equal to 1 cm above a surface of digitizer, the digitizer provides x and y coordinates; (b) long distance: height exceeding 1 cm, the only information available is a time stamp that indicates the time that a specific stroke has spent at long distance. Although short distance has been used in several papers, long distances have been ignored and will be investigated in this paper. In this paper, we will analyze a large set of databases (BIOSECUR-ID, EMOTHAW, PaHaW, OXYGEN-THERAPY, and SALT), which contain a total amount of 663 users and 17,951 files. We have specifically studied (a) the percentage of time spent on-surface, in-air at short distance, and in-air at long distance for different user profiles (pathological and healthy users) and different tasks; (b) the potential use of these signals to improve classification rates. Our experimental results reveal that long distance movements represent a very small portion of the total execution time (0.5% in the case of signatures and 10.4% for uppercase words of BIOSECUR-ID, which is the largest database). In addition, significant differences have been found in the comparison of pathological versus control group for letter “l” in PaHaW database (p = 0.0157) and crossed pentagons in SALT database (p = 0.0122).

中文翻译：

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在线手写中短距离和长距离空中轨迹的比较研究。

现有的有关在线手写分析以支持病理诊断的文献已经利用了空中轨迹。生物特征安全应用程序中发生了类似的情况，其目的是使用其签名或手写物来识别或验证个人。这些研究没有考虑笔尖到书写表面的距离。这是由于以下事实：当前的采集设备不提供高度形成。但是，区分两个不同高度的运动是非常简单的：（a）短距离：数字化仪表面以下的高度等于或小于1厘米，数字化仪提供x和y坐标 （b）长距离：高度超过1厘米，唯一可用的信息是一个时间戳，指示特定笔划在长距离上花费的时间。尽管在几篇论文中都使用了短距离，但是长距离却被忽略了，并将在本文中进行研究。在本文中，我们将分析大量数据库（BIOSECUR-ID，EMOTHAW，PaHaW，OXYGEN-THERAPY和SALT），其中总共包含663个用户和17,951个文件。我们专门研究了（a）不同用户档案（病理和健康用户）和不同任务在地面，近距离空中和远距离空中花费的时间百分比；（b）潜在使用这些信号来提高分类率。我们的实验结果表明，长距离移动仅占总执行时间的一小部分（在签名的情况下为0.5％，在最大的数据库BIOSECUR-ID的大写单词中为10.4％）。此外，在PaHaW数据库中字母“ l”的病理学和对照组比较中发现了显着差异（p  = 0.0157）和SALT数据库中的交叉五边形（p  = 0.0122）。