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Hi Ryan, I was reading the python listing openmms_controller_livox.py, I state that I am not an expert programmer, but very basic and I saw that this listing in addition to doing tests, checks the status of the buttons connected to the raspberry via GPIO interface and creates the files with the livox and utc data, I understood that through a serial port you receive the string with the utc data from the apx18 and then formats them, then I noticed the call to the openpylivox listing that allows you to extrapolate the real lidar data and in case it was a horizon also the data of its internal imu, but I did not understand where you extract all the gnss and imu data from the apx18. Maybe I will ask stupid questions, but I don’t have such in-depth knowledge of programming, but I would like to be able to extrapolate data from a cheaper gnss and imu sensor by modifying some parts of openmms, with the help of an experienced programmer that I am trying to involve to develop a decidedly free system very expensive sensors like APX, if I can I would like to contribute to your project but I need information on the software to explain it to the programmer. Thanks Francesco Italy
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Hi Francesco,
Your observations regarding the serial data being transmitted from the APX-18 to the Raspberry Pi computer are correct. However, this serial data stream is only used for Quality Assurance purposes immediately following data collection with an OpenMMS sensor (ideally while the operator is still in the field). I’m hopeful that viewing the OpenMMS Software Flowchart, found here, may help in your understanding of ALL the datasets collected by an OpenMMS sensor. Stated a different way, this serial data stream does not contain the low-level ‘raw’ GNSS and IMU observations from the APX-18 sensor. Those observations are stored directly within the built-in ~8GB of storage on the APX-18 itself. After completing data collection, the operator connects directly to the APX-18 via an ethernet cable and uses a web browser to navigate through the APX-18’s WebUI and download the respective .T04 binary file (see here for more details). All the ‘raw’ GNSS and IMU observations are contained within this .T04 file which is imported into the Applanix POSPac UAV post-processing software application, and processed with GNSS reference station data to produce the Smoothed Best Estimated Trajectory (SBET) ASCII file (see here for more details). It is this exported trajectory file that is then utilized within the OpenMMS software suite to produce a true colour georeferenced point cloud.
I hope my explanation helps your understanding of the GNSS+IMU data processing involved with the OpenMMS v1.3 solution.
Thanks for your interest in OpenMMS and for the question!
Ryan
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