Carrier phase observations generally have smaller noise level than code measurements, so they have been used for high-precision GNSS positioning techniques such as Real Time Kinematic and Precise Point Positioning. However, ambiguity integers of the carrier observables should be newly determined when even one cycle is slipped, which might seriously degrade its performance. Thus, a cycle slip detection technique is essential for the carrier-phasebased positioning system, and a lot of cycle slip detection methods has been suggested. Many of them is based on assuming an ionospheric delay varies slowly over time. They assume that the rate of change in ionospheric delay is negligible, which is valid only in the mid-latitude regions. During highly active ionospheric periods or in high latitude regions (e.g. Alaska), these methods cannot be used because the ionospheric variation is far larger than its noise level. In this paper, we propose a method to detect cycle slips by comparing the rates of change in ionospheric delay from various combination of triple-frequency carrier phase measurements. We used GNSS observation data logged from a reference station of Alaska in 2015. This technique can be used in region with severe ionospheric conditions and be able to robustly detect cycle slips compared to existing methods.

Keywords: triple frequency, cycle slip-detection, high ionospheric activities