"Why is POGO always lowballing the walking distance"

#PokemonGO: I always felt like the POGO walking counter was off (say: too low), so today I walked (courtesy of google maps) 10.8 km in one go, but POGO only captured 7.1 km (started a 10 km egg at the beginning). This means it registered only two thirds of the actual distance.The path consists of many long straights (so the low sampling rate should not be a big issue), I always had POGO on the display, there was no connection or GPS drop the whole time as far as I could see. I walked normal speed, approx 5 km/h, never much faster.I regularly checked the egg counters and one time I saw that between two counter updates on a looong straight road, it increased like 300 m for a part which is more than 700 m long according to google maps.How can I increase the accuracy of the counter? Being cheated of a third of the distance is just annoying... via /r/pokemongo http://bit.ly/2EUbAd4