I seriously considered tossing my iPhone and Android smartphones into the brown waters of the Thames. How liberating, if not exhilarating, it would have felt. But I took a deep breath, stepped away from the bridge railing, put both devices back into my pockets and continued along my confusing trajectory.\nWhat had pushed me to the edge? Two words: "GPS navigation."\nI recently spent almost three weeks in London. If you\u2019ve been to the U.K. capital, you know how confounding it can be for visitors. Streets meander and suddenly change names \u2014 with only a street sign here and there to assist. In most places, there are no visible high rises to ground you.\nHaving visited London in the past, I knew what to expect, navigation-wise. I was also trying to minimize AT&T\u2019s expensive international data roaming charges on my iPhone 5s.\nSo I armed myself before leaving the U.S. with two iOS apps, CoPilot Premium USA ($8) and Garmin\u2019s viago ($2), both of which offer downloadable maps for purchase for European countries and other regions.\nI also borrowed a portable GPS device from Garmin, the nuvi 3597LMTHD ($330 list price) and equipped it with optional maps for the United Kingdom and France. And I used a low-end Samsung Galaxy Fame Android smartphone with a one-month unlimited data SIM card purchased in London, with the goal of using Google Maps and Google Navigation.\nI was curious to see which of these options fared the best. As you may have guessed by now, each led me astray in one way or another.\n\n* CoPilot Premium. Faced with a nearly endless to-do list before departure, I forgot to download the CoPilot Premium U.K. map\u00a0at home. When I tried installing it over Wi-Fi in my rented flat, the download kept freezing and stopping. I received the same error message: \u201cInternet Connection Not Found! Try again shortly.\u201d It\u2019s a shame, because in the United States, CoPilot and its downloadable maps are a fairly solid smartphone GPS option.\n* Garmin viago. I'm a fan of viago (see my review) and had downloaded and installed the necessary map for London navigation on my iPhone before leaving home. But the app stalled whenever I tried to look up a destination while out and about in London, with cellular data turned off. (The iPhone 5s has built-in GPS, so you shouldn\u2019t have to rely on cellular data if you have an app that supports directions via downloaded maps and content.)\n* Garmin nuvi. The Garmin nuvi, which works well in San Francisco, repeatedly failed to find a satellite in London. The device also doesn\u2019t offer pedestrian or transit modes, so it wouldn\u2019t have been very useful for walking even if it had fixed on a satellite. (Seriously though, why don\u2019t all dedicated GPS devices offer pedestrian modes?)\n* Google Maps. Next I tried Google Maps on the Samsung phone. Folks, there\u2019s a good reason Google says its Maps pedestrian mode is in "beta" \u2014 it had me going in more circles than the London Eye. Another American I met there had similar issues with Google Maps.\n* A surprise winner: Citymapper. Finally, acting on another friend\u2019s advice, I downloaded Citymapper, which is free for both iOS and Android. Of all the options I tried, this app proved to be the least exasperating. (Sorry, that\u2019s as much enthusiasm as I can muster.)\n \nCitymapper on Android\n\nThe app, which covers only a handful of major cities (including London), offers pedestrian, transit, cycling, taxi and other routing modes. It doesn\u2019t give you turn-by-turn directions, however. Instead, the app shows your route on a map, with start and end points and a familiar pulsing blue dot to indicate your current position.\nThis isn\u2019t ideal, because you have to look at the screen frequently. And the Android app, unlike the iOS version, annoyingly overlays useless information on the map. As a result, I had to pinch and zoom in on the map to get a better view. Whenever I tapped the GPS icon to see my current position, the map zoomed back out and I had to pinch and zoom in again for a closer look. Sigh.\nThat said, Citymapper was far more efficient in getting me from point A to point B than Google Maps. Its search function is excellent. And I like how it estimates taxi fare, walk time and even how many calories you\u2019re likely to burn when walking.\nUltimately, my experience in London reminded me of how much GPS technology has to improve before it\u2019s consistently accurate and reliable, especially for pedestrians. In the meantime, if you find yourself in London, I recommend investing in a good paper map, asking locals for directions and using a combination of your smartphone\u2019s GPS and compass to figure out where the heck you are.