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Online Vs. Offline: The Android GeoData Conundrum



At the time this post is being written, virtually all Android devices being sold and used are mobile phones. Most of these mobile phones come with data plans that can stream data (3G/4G) on demand; they also  come with WiFi capability, so that you can get equivalent data directly off a wireless network. But what if you’re in an area that doesn’t have cellular data coverage or WiFi? For geodata, that can be a big problem.

1. Many commonly-used geographic apps, like Google Maps, Google Earth, Google Navigation, Layar, etc., require that a data connection be present to work. You can check this yourself by shutting off wireless data connectivity completely on your Android unit. Set it into “airplane mode” to turn off the cellphone connectivity, turn off the Wifi as well, then start up Google Maps. You may see a part of a map leftover from the last time you used it, but that’s it; zoom in/out, or scroll to a different area, and nothing will show up. You’ll eventually get an error message saying that the app can’t connect to the network.

Most people will spend most of their time in an area where some kind of wireless data connectivity is present. But if you check out the coverage map for Verizon, generally considered the carrier with the best overall coverage, you can see that there’s still a fair amount of the country that doesn’t have coverage, especially west of the Mississippi:

Zoom in closer, and you’ll see pockets of missing coverage even in areas that look completely solid above. Many of those area will never get decent data coverage, either because they’re too sparsely populated, or because topography/access makes coverage difficult to impossible to achieve. In those areas, online geodata will probably never be available, and your Android unit won’t be able to use geographic apps that require online access.

2. Phones had dominated Android unit sales up to now, but Android slates, tablets, media devices, etc. are coming soon. While some of these will have 3G/4G connectivity options, others won’t; that reduces their data connectivity coverage footprint to just those areas where they can get a WiFi connection. Adding 3G/4G  connectivity can be expensive, $25-30 a month, exceeding the cost of the hardware over its lifetime. So are those units going to be limited to only having geodata available only where there’s WiFi? If so, their utility as mobile geography tools will be severely crippled.

3. Finally, some wireless data providers are looking at limiting data bandwidth; ATT has already capped monthly consumption at 2 GB a month, with massive charges if you run over, and Verizon has long been rumored to be looking at similar caps. If you’re downloading large amounts of geographic data over such connections, like aerial imagery, you could easily bump up against those limits. WiFi downloads won’t have those limitations, but if you’re going where there’s no WiFi, that’s not a big help.

The solution is obvious – the ability to store data for an area so that it will be available even if there’s no connection. In other words, “data caching”. That way, you could download large amounts of data for a specific area over a fast, cheap WiFi network, and then access it quickly in areas that either have no connectivity, or connectivity limited by bandwidth caps. I think the master vision of Google and the wireless companies is that we’ll always be connected, and therefore this won’t be an issue. But that’s not the case right now, and I doubt it ever will be. I hope that data caching will be added to apps like Google Maps and Earth that currently lack it, but I haven’t seen any signs of that coming soon.

However, there are already a number of Android apps currently available that can cache online map imagery for later use offline; other apps can take map data converted into special formats, and use it offline. I’ll be reviewing a fair number of those apps over the coming months, starting next week with reviews of two apps that cache topographic and OpenStreetMap data for offline use. They have limitations, and the range/types of data available through these offline apps doesn’t match that of online apps, but they make Android units geographically useful in places where they’d otherwise be useless.

While I’m on this topic, a tangential word of warning. I’ve been reading the specs of a number of Android devices slated to come out over the next six months, and most of them include “GPS”. But their definitions of what constitutes “GPS” seem to vary. With true GPS, they’re picking up signals from GPS satellites, and converting those to a location; these will work anywhere in the world, regardless of whether the units have access to wireless signals. But for some units, if you dig deeper into the specs, the manufacturers talk about “network GPS” or “antenna GPS”, where location is determined by how close they are to wireless hotspots or cellular base station antennas. This technique is a useful adjunct to true satellite GPS, especially in urban areas where satellite visibility can be blocked by tall buildings. But it’s not in any sense an acceptable substitute for true satellite GPS, and shouldn’t even be called “GPS”. Not only is it far less accurate than true GPS even in the best case, it doesn’t work at all if you’re out of range of the cellphone network or hotspots. If the specs say “assisted GPS”, that’s probably OK, but you should still read the fine print. True assisted GPS is a augmentation to satellite GPS: proximity to a cellular antenna is used to narrow down your initial location, and provide information that lets your unit pick up satellite data more quickly. But I’ve also seen “assisted GPS” used to describe units that pick up location data from antennas/hotspots; once again, not acceptable. If you want to record geographic data with your Android unit, accept no substitutes – only buy Android devices with true satellite GPS that works anywhere. End of rant.


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7 Responses to “Online Vs. Offline: The Android GeoData Conundrum”


  1. 1 Buddha

    “…If you want to record geographic data with your Android unit, accept no substitutes – only buy Android devices with true satellite GPS that works anywhere. End of rant.” So what Android phones are out there (besides the failed Garmin phone) that support true sat GPS hardware? Much of what I’ve seen so far have only been the aGPS hardware. I’d be great if at some point in time there’d be a list of recommended Android phones & apps for mapping.

    Great work on the new site!

  2. 2 Goya

    One of the disadvantages of online maps are the enourmous roaming costs. if I stay in Belgium my 1Gb dataplan is largely sufficient, but one I drive 200 km I find myself paying 3.1$ per Megabyte (!). on some networks the price rises up to 16.5$…
    So caching maps would be a very welcome feature…

  3. 3 leszekp

    Most smartphones have true satellite GPS; for example, my Droid X has full satellite GPS. True assisted GPS is normally a supplement to this, not a replacement, but the specs on some units are equivocal about this. For example the upcoming Notion Ink Adam tablet had originally listed aGPS, but if you read the specs you realized that meant just network/cellular positioning, not true GPS (they later added true GPS to the specs).

    To test a phone to make sure it has true satellite GPS, put the phone in airplane mode, which turns off cellular and WiFi connectivity, then run a GPS status program to see if it can get a position. If it can, you’re good to go. I’ll have posts on good GPS status programs in the near future.

  4. 4 leszekp

    $3.1 a megabyte? Wow! Here in the US, ATT charges .05 per megabyte over their limit of 2 GB, which I thought was expensive. That’s why I went with Verizon, which has “unlimited” (actually 5 GB limit) for the same price.

    Lots of options for both caching online maps, and creating your own maps as well, for the Android. Too many, maybe, as reviewing all of them will take some time. But I will be covering as many of them as I can.

  5. 5 tonyf

    Would love to find out about creating my own maps or using geotiffs in a GPS app for HTC desire. Will be doing a long car trip away from mobile coverage, and want to cache maps. Australia.

  6. 6 leszekp

    My Droid X is having odd battery issues right now, and I’m waiting for a replacement. If it comes as scheduled (Thursday), I’ll try to put up some posts on this topic next week. First two will be on apps that can create offline maps for a number of Android apps, then I’ll cover one or two apps that display the maps.

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