Overdrive GPS issues with iPad

TJK · EVDO Newbie Joined: 29 Jul 2010 Posts: 2

My Overdrive works great wherever I travel for data access. I have yet to encounter any issues. In fact, I currently am on a remote lake where Sprint claims zero coverage and yet I am getting sufficient connectivity for email and albeit slow web browsing. So, kudos.

However I am having a strange GPS issue. My first trip with the Overdrive was to Las Vegas. Upon getting to my hotel I was playing around with the settings by connecting to http://overdrive from the browser on my iPad and enabled GPS for the first time. It correctly nailed my position but now even after 2 months it seems to think my current location is the Flamingo Hotel on LVB no matter where I am. This is using the stock map app on my iPad.
If I go into the settings on the Overdrive it does return correct lat / lon and elevation data and will show correct position if I connect to the mapping application via the Overdrive control panel. But when I pop back out to Maps on the iPad I am back in Vegas. I have actually tested this with 3 different iPads, 2 of which have never been to LV and all think they are at the Flamingo. So, either Elvis has possessed my iPad or the Overdrive is fixated on that location.

The only exception was on a recent trip to Allentown, PA where it retuned correct location data through Maps only to be back in Vegas the next time I turned it on.

Any ideas?

Dwayne · Posted: Thu Jul 29, 2010 5:57 pm Post subject:

The short version of the explanation is quite simple. Using a mobile hotspot (such as an Overdrive, or MiFi) for positioning applications should NEVER be considered reliable.

Here's the longer explanation . . .

The problem is that you are not using GPS at all. You are using WPS (WiFi Positioning System). Instead of using a GPS chip to find your position, your iPad is using it's WiFi radio to find nearby WiFi access points (WAPs). It will find the nearby access points and look up their MAC address using a centralized database over the Internet (like SkyHook Wireless' database). Based upon your relative position to the WAPs (measured by the visibility of various WiFi networks and latency to each of them), it attempts to estimate your position.

The way that the WAPs get into the database is by companies, such as SkyHook Wireless, driving specially outfitted vehicles that essentially drive around and look for WiFi networks. When they find one, they record the GPS location and MAC address of the network in a big database. That's where your iPad looked up your position.

The problem you are experiencing is because WPS is based upon one VERY BIG flaw . . . the assumption that WiFi networks don't move. In order for WPS to work, you have to depend on the GPS coordinates of various WAPs staying stationary. For home and office WiFi networks, that's a reasonably safe assumption. But for mobile WiFi neworks, it causes major problems.

So . . . here's your problem. Your Overdrive's position was recorded while you were in Las Vegas. It was entered into the database with that location. So now when your iPad looks for your location, it sees your Overdrive and looks it up in the database. The database returns the location where it was recorded in Las Vegas and that's what is displayed in the Maps application on your iPad.

The very same thing happened to me. I went to SkyHook and had them remove my WAP from their database (I contacted them via e-mail and they were happy to help). It took less than a month for it to end up back in their database at another location (caught me eating lunch at Chili's). They don't have a way to completely keep it out of the database permanently as far as I know, so this is only a short-term fix.

Options:

(1) Replace your iPad with an iPad 3G. It has a real GPS chip built-in. Even if you don't use AT&T's 3G service, the GPS chip is still active and accurately finds your position. Only drawback is that you need a reasonably clear view of the sky for GPS satellite lock. If you don't have one, you need to rely upon WPS (which may be inaccurate) or cellular location data (which requires you to activate your AT&T 3G service).

(2) Don't use the built-in mapping app on the iPad. Instead, you can log into the web admin interface on your Overdrive (http://102.168.0.1), enable the OverDrive GPS, and click on the "Map Me" button. You will need to use a browser other than Safari on the iPad (like Perfect Browser) because Safari blocks the JavaScript popup windows generated when using the "Map Me" button. Now, the major drawback of this method is that it doesn't automatically refresh your position. You have to manually keep going back to the OverDrive's web screen and hitting "Map Me" every time you want an update.

(3) Some people claim to have gotten third-party GPS units (bluetooth, I think) working with the iPad using the built-in maps app or Navigon. Some had to jailbreak their iPad (which I don't recommend) but others didn't specifically say that in the posts I read. You'd just have to do a web search to find your options there.

TJK · EVDO Newbie Joined: 29 Jul 2010 Posts: 2

Dwayne- thanks very much for the informative reply. I have contacted Skyhook and am awaiting a reply.

I will definitely download an alternate browser and give that a try as well.

You would think that Skyhook would be able to recognize mobile WAPs somehow?

Dwayne · Posted: Sun Aug 01, 2010 6:29 pm Post subject:

Contacting SkyHook is only a temporary solution. There are too many companies doing what SkyHook does. They are only one of the databases used by some of these apps.

Identifying a device as a mobile router is actually not easy to do. They identify the network by MAC address. While a MAC address can be traced to a manufacturer, it would be traced to the manufacturer of the WiFi card, not the router itself. So there really is not easy way that I can think of to make it obvious to the systems recording nearby networks that the device is mobile.

Probably the better answer is for the router manufacturers to provide another, easier method for accessing the GPS data on the router. CradlePoint has done this, but for some reason Novatel and Sierra haven't. Using a web page to launch a static map is about all they can do right now. If they made it available in a choice of NMEA and KML formats (like CradlePoint), it would be much easier for applications to use the GPS data directly off the router.