Google Navigate guides Jaguar in Chickpet

Goolge Maps updated itself on my Samsung Android Note 2 and it has merged navigation into the map. Map has a a newer UI and looking slick. Reminded me to blog my experience.

Driving directions is based on several components

1)      Digital maps provided by providers like TeleAtlas ,  Navteq, etc. Crowdsourcing and open approaches are also taking off. This includes features like Points of Interest (POI) Petrol pumps, Hospitals, Business offices etc.

2)      Location sensing . GPS primarily . Smartphones can use information on location of cell towers (multilateration ) and WiFi hotspots to guess location. These are much less precise then GPS.

3)      Algorithms to route from one location to another.

4)      User Interface to search for locations and  provide options for routing ( Temples within 2 Kms, Hospital s, Avoid Toll roads, Fastest route, Shortest Route)

In the older days the entire stack was bundled and came in a  hardware box Personal Navigation Device ( PND) from providers like Garmin, Tom Tom etc. Now more open with Smartphones emerging as popular PND.

NeverLost gets Lost

My first experience with GPS based route navigation or driving directions was in the USA with Hertz NeverLost system   in late 1998. I had taken a sabbatical and was “updating “ myself at Wharton Business School. Over the weekend I decided to attend a celebratory event at a friend’s place in Long Island New York.  Another friend and we set off from Philadelphia, took the I95 and went on for miles and miles…It was late buy the time we were near the destination. The sun had set early  ( this was near Christmas in winter) and we were in some vast hinterland . It was miles and miles of wilderness . No houses, petrol stations etc. No sign of human settlements actually. And we were just about an hour out of the city.  It took some time to realize the NeverLost was wrong and we were off our track. The system kept asking us to turn off right or left but we could not find the side road to turn into. Then we realized it is wrongly calibrated. It misses the turning point by  several minute or some 100 or more yards. So if we went back and took the turn we were on the “correct’ road.

It is only when lost in a vast uninhabited part of USA you realize how big the country is. It was quiet a journey . And in those days cell phones were not so easily available…. How we managed is a different story but we did reach our host house ( a few hours late)…

Apparently this problem still continues ( See http://voices.yahoo.com/never-lost-review-hertz-gps-navigation-6877890.html)

Tom Tom was great.

Subsequently I used Tom Tom  a lot in UK and Europe during 2006/2007. This PND( Personal Navigation Device) was far more robust and accurate. The best thing was its ability to tell you to keep left or right on the correct lane to take a flyover or get out of a roundabout. Pretty impressive.  However I had an embarrassing episode with this. Overconfident in this device I decided to take my daughter who was visiting us in London to Oxford. Lo and behold that day ( must have been a unduly overcast cloudy day I thought but later learnt moving the device hundreds of mile from last used location causes it to try to reload almanc data  See below ) the Tom Tom did not get a GPS lock on its current location till ages ( over 15 minutes) . By that time I was truly off the rails in South London trying to get past Heathrow to A40/M40.

Google Navigate beta in India

The first use of Google Navigate(which talks  Driving directions)  in Bangalore was interesting to say the least. It took a long while to load and then started guiding thru streets unknown. The pronunciation of Indian streets was funny and left me clueless what it was talking about.  However it seems to get better with passing days ( or I got used to its pronunciation?) .

Jaguar in Chickpet

In early days it had the bad habit of routing for the shortest path ( I guess) and that included really narrow lanes around Chickpet, cotton pet etc.  I was driving one Saturday early morning thru some narrow lane where on side of an already narrow lane was anyway taken up by hawkers carts and parked auto rickshaw. Lo and behold from a side lane a black Jaguar come out. Driven by a bearded young Iranian looking gentlemen dutifully following a Smartphone based navigator( assumed Google Navigate)  . Even in a small Hyundai i10 I was dreading the lane . Wonder what was going thru the driver of the Jaguar. It was a really risky drive for that car…

A nice feature is the ability to show traffic density ( Based on cellphone and GSM Cell Tower data). Initially it seemed to automatically reroute to avoid congested parts. This was unnerving to me. I wanted to be given an option not silently turned into a new road I had never travelled. After I ignored this for some time it seems to have given up this habit. I prefer to check alternative routes at the start but once  selected I do not want any automatic re routing.

There were some days when the road Google suggested disappeared as a House or a construction had taken the road . Typically India. Also one way direction is not up-todate. Anyway the system was pretty fast in rerouting if I took a different route. It now seems to able to guide lane changes also most of the time.

I have used this driving round from Bangalore to Chennai, Tirupathi and it worked flawlessly. Impressed. And highly recommended.

Navigation while offline

An interesting discovery while on these drives was getting the map to work without an active data connection. The trick is to save a region of the map for off-line use while connected. This typically will be a few megabytes for a day’s travel ( 300-500 Mile ) . Start the routing while connected. Then even when you lose the connection routing will continue. You can actually shut of the mobile and wi-fi and only keep GPS radio on. Conserves power. You can also switch the display off and use voice guidance most of the time. My phone would work 8 + hours without recharge under these conditions.

Crowd sourcing Points of Intersect (POI)

It is still not very easy to find the nearest fast food restaurant, Hospital or Petrol station. However You can add these using Google Mapmaker and in due course they will become part of the public data-set. You can also correct mislabeled features. Or wrong locations. This is quiet frequent occurrence. Many not-so-marquee-hotels will not be where the map says they are. Just ask some helpful folks. You will not be too far away normally within a Km.

Tom Tom better UI

The TOM TOM UI is better suited to navigation. It is more intelligent is showing POI like Petrol stations and fast food joints. It is also much easier to look up nearest Petrol station etc. Though Google offers to call the business it shows on the phone. Cool…

Routing is Not a solved problem

In the past I never knew the location well enough to pronounce on the routing of Tom Tom etc. But now that I have been using GPS navigation in a place I know intimately I realize the intricacy of routing. It is not a trivial or solved problem. Many times using local knowledge I would do much better then Google Navigate.

However I was greatly impressed by the estimate of time to reach a destination. Google Navigate is pretty accurate. Takes into account real world speeds that we get rather then theoretical speed limits of the road. Tom Tom used to be way off.

Getting under the Hood of GPS devices

The next intensive usage was in 2009 but for Golf and not driving.

I wanted to get a accurate measure of the distances I hit the ball with different clubs and researched on using a GPS enabled Smartphone. That is when I realized how this works and what goes on underneath the GPS device.  Most GPS chips locate 3-4 satellites and triangulate the position. This has a circle of error over 40 feet . Thus you may be on a fork in the road and the GPS device cannot reliable know which road you have gone into. I saw this in action. The dot representing my car used to suddenly diverge from the road I had turned into but snap onto the right road quickly after some time.  This was no good. A error of 40-80 feet is 2 or more  club difference .    Newer chips Like SIRF III lock into 8-12 satellites and can be accurate to 4-6 feet. And catch GPS signal even when inside the glovebox!!! (  http://www.mo-co-so.com/Sirf-III-USB-GPS-Receiver-p/mcs-gps-usb.htm ) This is what I selected.

The time to First Fix (TTFF) is normally a minute or less but would be 15 minutes also. I had many issues getting an initial fix and then figured out updating almanac data over the internet was the only foolproof way.

The  GPS satellites  broadcast  two  types  of  data,   Almanac   and  Ephemeris.   Almanac  data is course orbital parameters  for  all Satellites (SV) .  Each SV broadcasts Almanac data for ALL SVs.  This  Almanac data  is  not  very precise and is considered  valid  for  up  to several  months.   Ephemeris data by comparison is  very  precise orbital  and  clock correction for each SV and is  necessary  for precise  positioning.  EACH SV broadcasts ONLY its own  Ephemeris data.   The ephemeris data requires 18 to 36 seconds before it is received, due to the low data transmission rate.  This data is only considered valid for about 30  minutes.  The Ephemeris data is broadcast by each SV every 30 seconds. When the GPS is initially turned on after being off for more than 30 minutes,  it “looks” for SVs based on where it is based on the almanac  and current time.  With this  information,   appropriate SVs can be selected for initial search. When  the  GPS receiver initially locks onto a  SV,  the  display then shows “hollow or red ” signal strength bars.  At this  time,  the Ephemeris data has yet to be completely collected.  Once  the ephemeris data is collected from EACH SV in turn,  the associated signal  strength  bar will turn “solid or green ” black and then  the  data from that SV is considered valid for navigation.( I used GPSTest app from Chartcross on Android)

If power is cycled on a GPS unit,  and when turned back on,   the Ephemeris data is less than 30 minutes old,  lock-on will be very quick since the GPS does not have to collect new Ephemeris  data.  This is called a “warm” start. If  it  is later than 30 minutes,  this is  considered  a  “cold” start and all Ephemeris data will have to be recollected.   If  the GPS has moved more than a few hundred miles  or  accurate time  is lost,  the Almanac data will be invalid and if  you  are far  enough off,  none of the SVs that the Almanac thinks  should be  overhead will be there.  In such case,  the GPS will have  to “sky search” or be reinitialized so it can download a new Almanac and start over. The almanac data is transmitted at a very low rate ( teletype rates for robustness) . It can take up to 12.5 minutes for the GPS receiver to receive full almanc data . ( See http://en.wikipedia.org/wiki/GPS_signals ).

Modern Smartphone allow you to update the Almanac data by connecting via the internet to well known servers. This greatly enhances TTFF. This is part of Assisted GPS or A-GPS .  Cell Towers can provide this information if the mobile operator has installed A-GPS server. This can be done over the mobile signal and does not require a internet connection.