[kbk_75]

Is there any truth to the story about some company offering a Sat Nav service here in India? Personally I doubt the financial viability of undertaking a road-mapping service in software form, because the numbers it will sell will be virtually non-existent, but still...any truth or is it all rumours?

[vivekiny2k]

with a little less precision, GPS works well in india. And i have seen some companies sell indian maps. I believe they started making these maps some 5 yrs ago. i don't see why this can not be done. in addition to road maps, this excercise is useful for a lot of other purposes.

[Xsailor]

Originally Posted by vivekiny2k

with a little less precision, GPS works well in india.

Hi,

Could not understand the precision part of your post! Why "with a little less precision"? Pray elaborate.

Cheers

[kbk_75]

I guess what I'm trying to figure out is whether there is any software available on CD/DVD that would be compatible with the Sat Nav feature on some imported cars?

[satish_appasani]

Some good news to all the people who are hoping to put GPS in their cars. I was searching Google for Indian maps and came across this one.

http://vitotechnology.com/en/products/mapofindia.html

[kbk_75]

Well, I really don't think that is going to suit the purpose of Sat Nav. They have only mapped the country on a 1:1 million scale, so it may help you to figure out if you are generally headed in the right direction of another city / state, but it would be pretty useless for street navigation, which is what Sat Nav really addresses.

Edit: They seem to have a product called SmartMap that may be useful though, but does it only work with PocketPCs? Anyone with any idea about this application?

[devarshi84]

To use GPS in a big country as India is really useful.
It is a good attemp. You cannot expect it to run successfully in the initial period.the more the people use it, the more development will take place. I believe it will take around 5 years for it to be fuylly functional and successful.

[vivekiny2k]

by precision, what i meant is how correct ur location is, as given by the GPS receiver. I belive in US if us position is given as X, the error can be 3 meters +/ either sides. so u are still having a very good idea of where u are, hence the street navigation is easy.

but since the satellites are not so favourably positioned for india, the error in india might run close to 100-200 meters. I am not sure about that though.

still, on a highway, it will be useful if u have a map and a GPS device, to gauge the distance and direction.

I am talking from a point of view of makeshift navigation mechanism. which can be made from a pocket Pc/laptop, and a GPS receiver.

It may not at all suit the navigation systems already installed in cars, since there cud be incompatibilty in the maps we get and the software used in the car.

[vivekiny2k]

just went through the vito site, the map is cheap, but the software to use it costs 29$. i am going to buy the map to see how good it is. but again, it's no use if the GPS can not locate me well on the map :-(

PS: sorry about the SMS lingo in previous post, i just got carried away. :-)

[Xsailor]

Hi Guys (and those who are uninitiated in the ways of the Global Positioning System )

Name and Usage
SAT NAV : The word SATNAV referred to a older version of Satellite Navigation. This system too was developed by the US DOD but used a different technology whereby the user was not continuously updated on his position. User was given "fixes" (a cross hair consisting of a Lat and Long) at frequent intervals (depending on the Almanac of the satellite and the position of the user). In between the fixes, the receiver would guide the user on DR (dead reckoning) based on user-input courses and speeds. As is evident, this was not a real time positioning system and thus not very reliable.

GPS : GPS (Global Positioning System) is the current system. It works in real-time and with every look at the Display showing a Lat and Long, you may plot a fix. The only time this does not hold good is when the receiver is unable to obtain signals from a third sat and usually indicates the same to the user (Magnavox GPS display units shows "UNRES" which stands for unresolved).
The nominal GPS Operational Constellation consists of 24 satellites that orbit the earth in 12 hours. There are often more than 24 operational satellites as new ones are launched to replace older satellites. The satellite orbits repeat almost the same ground track (as the earth turns beneath them) once each day. The orbit altitude is such that the satellites repeat the same track and configuration over any point approximately each 24 hours (4 minutes earlier each day). There are six orbital planes (with nominally four Sats in each), equally spaced (60 degrees apart), and inclined at about fifty-five degrees with respect to the equatorial plane. This constellation provides the user with between five and eight sats visible from any point on the earth.

Funda
Basically, very simple. If I were to say you are 100m from your your doorbell, you could be anywhere on the circumference of a 100m radius circle from your doorbell. Further, I also say that you are 25m from your neighbor's doorbell (across the road, if you may!), you could be only at two positions, where both the circles interact - the 100m and the 25m. If I further state that you are also facing the row of houses which includes your own, you will be 100% sure of the position as only one such position exists (all assuming the same height above sea level). The GPS system uses sats instead of doorbells and of course, a lot of techno wizardry.
The word precision in tech terms is used for GDOP (Geometric Dilution of Precision). GDOP is computed from the geometric relationships between the receiver position and the positions of the satellites the receiver is using for navigation - The more the angle of cut between the position lines drawn by the Sats, the better is the GDOP.

Accuracy
Till about a few years ago (can not quite recall the date now having quit sailing for a while!), there was SA (Selective Availability) in force by DOD - in simpler words, an induced error. Even then, the accuracy was +-250meters. But with SA gone, the accuracy is down to +-30 meters and if using DGPS correction signals, accuracy is within +-5 meters - this however is limited to the availability of DGPS stations in the area.

Originally Posted by vivekiny2k

by precision, what i meant is how correct ur location is, as given by the GPS receiver. I belive in US if us position is given as X, the error can be 3 meters +/ either sides. so u are still having a very good idea of where u are, hence the street navigation is easy.but since the satellites are not so favourably positioned for india, the error in india might run close to 100-200 meters. I am not sure about that though.

Also, irrespective of the nationality, the accuracy of GPS receiver remain the same (Of course, the fixed and variable errors remain to effect each user individually depending on atmospheric conditions, location and receiver/antennae mounting).

Cheers