Even the best collection of positioning and orientation data can be significantly improved by post-processing. In real time, depending on the collection method, users of Applanix equipment can get an accuracy of 5-10 centimeters. Using POSPac software to post-process that data, they can get it down to 2-3 centimeters.
POSPac MMS is the comprehensive version of the software, and its uses include marine, airborne, and land platforms; POSPac UAV is a subset of that, restricted to only UAV applications. Additionally, Applanix has developed a version for use with backpack systems used to survey on foot. “You can strap one of our systems onto pretty much anything that moves, then post-process the data later,” says Terence Fu, a software engineer and POSPac’s Development Manager.
POSPac has the same GUI architecture as Trimble Business Center (TBC). Typically, however, TBC is used for static surveys and POSPac for kinematic ones, usually integrating GNSS and inertial data, but a GNSS-only version is also available. POSPac runs on Windows 7 and Windows 10 platforms, though Applanix will likely discontinue support for Windows 7 sometime in the next couple of years.
There are many UAV servicing and direct georeferencing applications for POSPac. “It’s an emerging market,” says Fu “We have many UAV customers”.
Traditionally, one of the best methods to post-process positioning data collected in the field has been to use a local reference station in order to cancel out the common errors. In the last few years, however, POSPac has integrated a new processing mode, called PP-RTX, which stands for Post-Processed Real-Time Extended. It is a service that uses Trimble’s own global network of reference stations to provide global satellite corrections.
POSPac users logs their rover data with an Applanix POS or APX system. Then, through the Internet, they download the corrections from the RTX service, which POSPac uses to cancel out the errors and improve the accuracy of the final positioning solution. To further improve the quality of the solution, they can then combine the GNSS data with that from the inertial sensor.
The main benefit, Fu points out, is that you don’t need to own, configure, set up, and pay for your own local reference base station, which is often a paid service. “With PP-RTX, you log your data then click one button in POSPac and it will download the data, run the QC process, and do the post-processing. The accuracy is phenomenal, given how simple it is. It is nearly as good as having a local reference station.”
Additionally, the data is available right away, whereas a base station sometimes requires longer wait time to transmit, depending on your set-up.