They are referring to integer ambiguity resolution, which is the final step in getting a dual-frequency differential GPS position down to centimeter accuracy.<p>This [1] is a good explanation. It does require a GPS receiver capable of carrier phase tracking, which your cell phone isn&#x27;t capable of. The cheapest I&#x27;ve seen is this uBlox [2].<p>[1] <a href="http:&#x2F;&#x2F;www.navipedia.net&#x2F;index.php&#x2F;Carrier_Phase_Ambiguity_Fixing" rel="nofollow">http:&#x2F;&#x2F;www.navipedia.net&#x2F;index.php&#x2F;Carrier_Phase_Ambiguity_F...</a><p>[2] <a href="https:&#x2F;&#x2F;shop-america.u-blox.com&#x2F;en&#x2F;usd&#x2F;3~130~AMERICAS&#x2F;Position-Time&#x2F;High-Precision-GNSS&#x2F;NEO-7P-NEO-6P" rel="nofollow">https:&#x2F;&#x2F;shop-america.u-blox.com&#x2F;en&#x2F;usd&#x2F;3~130~AMERICAS&#x2F;Positi...</a>