Department of Geomatics Engineering, Schulich School of Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada.
Sensors (Basel). 2023 Jan 10;23(2):777. doi: 10.3390/s23020777.
Precise position information available from smartphones can play an important role in developing new location-based service (LBS) applications. Starting from 2016, and after the release of Nougat version (Version 7) by Google, developers have had access to the GNSS raw measurements through the new application programming interface (API), namely android.location (API level 24). However, the new API does not provide the typical GNSS observations directly (e.g., pseudorange, carrier-phase and Doppler observations) which have to be generated by the users themselves. Although several Apps have been developed for the GNSS observations generation, various data analyses indicate quality concerns, from biases to observation inconsistency in the generated GNSS observations output from those Apps. The quality concerns would subsequently affect GNSS data processing such as cycle slip detection, code smoothing and ultimately positioning performance. In this study, we first investigate algorithms for GNSS observations generation from the android.location API output. We then evaluate the performances of two widely used Apps (Geo++RINEX logger and GnssLogger Apps), as well as our newly developed one (namely UofC CSV2RINEX tool) which converts the CSV file to a Receiver INdependent Exchange (RINEX) file. Positioning performance analysis is also provided which indicates improved positioning accuracy using our newly developed tool. Future work finding out the potential reasons for the identified misbehavior in the generated GNSS observations is recommended; it will require a joint effort with the App developers.
智能手机提供的精确位置信息在开发新的基于位置的服务（LBS）应用程序中起着重要作用。从 2016 年开始，在谷歌发布 Nougat 版本（版本 7）之后，开发人员可以通过新的应用程序编程接口（API）即 android.location（API 级别 24）访问 GNSS 原始测量值。然而，新的 API 并没有直接提供典型的 GNSS 观测值（例如，伪距、载波相位和多普勒观测值），这些观测值必须由用户自己生成。虽然已经开发了几个用于生成 GNSS 观测值的应用程序，但各种数据分析表明存在质量问题，从偏差到从这些应用程序生成的 GNSS 观测值输出中的观测不一致性。这些质量问题将随后影响 GNSS 数据处理，例如，载波相位平滑和最终的定位性能。在这项研究中，我们首先研究了从 android.location API 输出生成 GNSS 观测值的算法。然后，我们评估了两个广泛使用的应用程序（Geo++RINEX logger 和 GnssLogger Apps）的性能，以及我们新开发的一个应用程序（即 UofC CSV2RINEX 工具）的性能，该工具将 CSV 文件转换为 Receiver INdependent Exchange（RINEX）文件。还提供了定位性能分析，表明使用我们新开发的工具可以提高定位精度。建议进一步开展工作，找出生成的 GNSS 观测值中存在的潜在行为异常的原因，这需要与应用程序开发人员共同努力。
