GPS World, June 2016
accessible through the three dots at the top of the screen File Formats The app currently logs data in a binary format that is dependent on the particular GNSS receiver An example is the nvd format shown in Figure 4 Once the data is in the cloud a variety of software tools are available to convert these files to other formats such as the widely used RINEX format Currently our post processing of nvd files stored in the cloud is done in a custom Python script that converts them to the RINEX format in batch mode To validate the generated RINEX format we use the TEQC tool provided by UNAVCO Software Architecture The Android OS implements threads as a way to let users run multiple tasks at the same time to manage multiple user interface updates or to perform various background actions Activity threads handle a users interaction with the main screen and GNSS configuration screens Other app specific threads are spawned by the main activity thread in response to user prompts The spawned threads perform specific actions asynchronously in the background so the user can continue to interact with the app while uploads are in progress In particular the main activity thread handles the users interaction with the main screen The activity calls the appropriate software functions that respond to button taps The main thread also updates the user interface with the latest status information and manages the creation of new threads for serial input output I O as well as uploads to Dropbox The GNSS receiver config activity thread presents the user with a lightweight text editor which captures all necessary GNSS receiver configuration commands In the current version of the app these commands are permanently stored in the smartphone internal bulk memory using the Android SharedPreferences module This can be easily extended in the future such as to store and download command configuration files to and from the cloud When a user toggles the Session Control button in other words a Start Session event the serial I O manager thread starts storing all the bytes received from a GNSS receiver to a GNSS session file The bytes are read from the smartphones USB serial data interface and written to a file in binary format The file and its properties are represented internally by a GNSS JUNE 2016 WWW GPSWORLD COM GPS WORLD 61
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