I would like to time-align RTC instances for two nRF9160s to within 100 µs, by synchronizing each RTC independently to a GPS 1PPS (one pulse per second) event. Does the nRF9160 GPS module make available a 1PPS signal and/or is there a GPS software event (callback) that can occur with a specified 1PPS latency variation?
In general, is there a link to documentation for the GPS module, such as a user guide, hardware reference, or software API (other than the GPS source code available on GitHub)?
Regarding your first question I need to come back to you.
Regarding your second question, additional information about the GPS can be found in the Objective Product Specification:
Please note the section about the GPS in the Development Status blog.