(Reference: Wikipedia.org)
The GPS is a space-based global navigation satellite system (GNSS) that provides location and time information in all weather and at all times and anywhere on or near the Earth when and where there is an unobstructed line of sight to four or more GPS satellites. It is maintained by the US government and is freely accessible by anyone with a GPS receiver.
The GPS project was developed in 1973 to overcome the limitations of previous navigation systems, integrating ideas from several predecessors, including a number of classified engineering design studies from the 1960s. GPS was created and realized by the US Department of Defense and was originally run with 24 satellites. It became fully operational in 1994.
In addition to the US GPS, other systems are also in use or under development. The Russian Global Navigation Satellite System was in use by the Russian military only until it was made fully available to civilians in 2007. There are also the planned Chinese Compass Navigation System and the European Union's Galileo Positioning System.
GPS and Assisted GPS (A-GPS) that are found in some mobile phones (e.g. iPhone) are not the same. A-GPS will be discussed at the lower sections of this page.
In this post, I shall comment on some of the GPS Personal Navigation Devices (PND) commonly available in Singapore. Note that the comments are base only on my personal opinions, preference and experiences.
Garmin Ltd. is incorporated in Switzerland, and its principal subsidiaries are located in the United States, Taiwan and the United Kingdom. Garmin, Bluechart, City Navigator, Colorado, Foretrex and Oregon are registered trademarks and Dakota, is a trademark of Garmin Ltd. or its subsidiaries.
Began as a brainstorming session of a handful of engineers around a card table in 1989, the company has evolved into a worldwide collaborative effort of thousands of employees. Garmin Corporation (listed in Nasdaq) is a unit of Garmin Ltd which has designed, manufactured, marketed and sold navigation, communication and information devices and applications (most of which are enabled by GPS technology). Garmin’s products serve automotive, mobile, wireless, outdoor recreation, marine, aviation, and OEM applications.
In Singapore, good deals for Garmin GPS PND may be found at the various computer and IT fairs which are available about 4 times a year. Authorised distributors in Singapore are:
· Navicom Technology Pte Ltd (regular participant in computer fairs)
· Oceantalk Pte Ltd
See link for list of authorised dealers and retailers in Singapore (too many to list here).
http://www.garmin.com.sg/distributor/singapore/
Notable sellers include JK Commercial, Challenger, AAAs Com Solutions, AA Singapore, Mustafa, Parisilk Electronics, etc.
Garmin PND are also available through parallel importers such as East Gear Pte Ltd (http://www.eastgear.com/) and also via Amazon.com (http://www.amazon.com/).
Comments
I am currently a happy owner of 2 3 Garmin GPS PND; 4 years old Nuvi 550 (waterproof), a 2 years old Nuvi 1460, and a few months old Nuvi 2597LMT (Australia set). IMO, the Garmin navigation engine is efficient and user experience is very pleasant with simple and straight forward GUI. Whether it is finding a "favourite" (waypoint), searching for a Point of Interest (POI), finding a destination using an address or Postal Code (only SLA & MSM maps), the process is simple enough for even the first time user. As for Text-to-Speech (TTS) function, my complaint is the lack of clarity in the voice used (both male and female voice); not the accent but the lack of clarity or sound fidelity. By the way, the FM TMC service (available on my N1460) was intended to provide real-time traffic services such traffic condition updates, alternative route around traffic to avoid delays, etc. Personally, I think the TMC sounds better than it works, especially during peak hours when traffic on almost every expressways or major routes are pretty heavy or jammed up. The availability and ability to use Mapsource (desktop based software) together with the PND helped a lot. I am able to backup or synchronise my waypoints and routing plans between my PC and PND. i.e. I can work on my PC to set up waypoints and plot intended routes before sending them to the PND. It was intentional that the 2 Garmin sets I own have the Route Planning function (not all models have it). Planning and saving routes in advance is a very useful function that provides lots of convenience and saves lots of time on the road.
IMO, one of the biggest PLUS enjoyed by Garmin PND in Singapore is the availability of community maps like Malfreemaps (MFM) and Malsingmaps (MSM). These communities release regular map updates and POI which are far more detailed than the Gamin NT maps, and they are available for download free. Although I have the Garmin City Navigator South East Asia NT maps (covering major metropolitan areas in Singapore, Malaysia, Thailand, Indonesia, Hong Kong, Macau, Philippines, and Bali.), I chose to use MFM during my trips to Southern Thailand, crossing West Malaysia in between. The NT map showed a lot less details of the streets and many POI available in MFM were not found in the NT, including major attractions such as famous restaurants or shopping centres.
Apart from the navigation and map support, I have to say the Nuvi 550 provided me with the luxury of using it on my beloved Honda Silver Wing, rain or shine. Yes, it is waterproof so I do not have to worry about losing guidance when it rains. Together with RAM Mounting systems, I was able to mount the PND firmly onto the bike without having to worry about it dropping off from the suction mount provided by Garmin. Good things come with a price, the RAM set costs about S$100+ (cradle, arm, lockable knob, diamond/base balls), an investment I never regretted.
With the preloaded and community maps, I enjoy the "best combination" of maps:
In my Nuvi 550... recognises only 1 map file (GMAPSUPP.IMG)
· MalFree MFM (micro SD) ... West Malaysia, Southern Thailand
In my Nuvi 1460... recognises multiple map files (######.IMG)
· Garmin City Navigator NT (preloaded) ... hardly use, on standby
· Garmin City Navigator SE Asia NT (micro SD) ... on standby
· MalSing MSM (micro SD) ... Singapore, West Malaysia
· MalFree MFM (micro SD) ... West Malaysia, Southern Thailand
In my Nuvi 2569LMT... recognises multiple map files (######.IMG)
· Garmin City Navigator NT Australia (preloaded) ... no issues with map for used in Sydney, Grand Pacific Drive, Canberra, Melbourne, Great Ocean Road, etc.
Despite being more pricey than other GPS makes/models, my personal preference is still for Garmin. I think the advantages is worth the extra investment.
For use on a motorcycle, I enjoy 2 big advantages with Garmin:
· There are waterproof units available.
E.g. Nuvi 500/550 (I own one), Zumo 550, Zumo 660.
· RAM mounts have dedicated cradles for Garmin units.
RAM Mount Cradles for GPSBegan as a brainstorming session of a handful of engineers around a card table in 1989, the company has evolved into a worldwide collaborative effort of thousands of employees. Garmin Corporation (listed in Nasdaq) is a unit of Garmin Ltd which has designed, manufactured, marketed and sold navigation, communication and information devices and applications (most of which are enabled by GPS technology). Garmin’s products serve automotive, mobile, wireless, outdoor recreation, marine, aviation, and OEM applications.
In Singapore, good deals for Garmin GPS PND may be found at the various computer and IT fairs which are available about 4 times a year. Authorised distributors in Singapore are:
· Navicom Technology Pte Ltd (regular participant in computer fairs)
· Oceantalk Pte Ltd
See link for list of authorised dealers and retailers in Singapore (too many to list here).
http://www.garmin.com.sg/distributor/singapore/
Notable sellers include JK Commercial, Challenger, AAAs Com Solutions, AA Singapore, Mustafa, Parisilk Electronics, etc.
Garmin PND are also available through parallel importers such as East Gear Pte Ltd (http://www.eastgear.com/) and also via Amazon.com (http://www.amazon.com/).
Comments
I am currently a happy owner of
IMO, one of the biggest PLUS enjoyed by Garmin PND in Singapore is the availability of community maps like Malfreemaps (MFM) and Malsingmaps (MSM). These communities release regular map updates and POI which are far more detailed than the Gamin NT maps, and they are available for download free. Although I have the Garmin City Navigator South East Asia NT maps (covering major metropolitan areas in Singapore, Malaysia, Thailand, Indonesia, Hong Kong, Macau, Philippines, and Bali.), I chose to use MFM during my trips to Southern Thailand, crossing West Malaysia in between. The NT map showed a lot less details of the streets and many POI available in MFM were not found in the NT, including major attractions such as famous restaurants or shopping centres.
Apart from the navigation and map support, I have to say the Nuvi 550 provided me with the luxury of using it on my beloved Honda Silver Wing, rain or shine. Yes, it is waterproof so I do not have to worry about losing guidance when it rains. Together with RAM Mounting systems, I was able to mount the PND firmly onto the bike without having to worry about it dropping off from the suction mount provided by Garmin. Good things come with a price, the RAM set costs about S$100+ (cradle, arm, lockable knob, diamond/base balls), an investment I never regretted.
With the preloaded and community maps, I enjoy the "best combination" of maps:
In my Nuvi 550... recognises only 1 map file (GMAPSUPP.IMG)
· MalFree MFM (micro SD) ... West Malaysia, Southern Thailand
In my Nuvi 1460... recognises multiple map files (######.IMG)
· Garmin City Navigator NT (preloaded) ... hardly use, on standby
· Garmin City Navigator SE Asia NT (micro SD) ... on standby
· MalSing MSM (micro SD) ... Singapore, West Malaysia
· MalFree MFM (micro SD) ... West Malaysia, Southern Thailand
In my Nuvi 2569LMT... recognises multiple map files (######.IMG)
· Garmin City Navigator NT Australia (preloaded) ... no issues with map for used in Sydney, Grand Pacific Drive, Canberra, Melbourne, Great Ocean Road, etc.
For use on a motorcycle, I enjoy 2 big advantages with Garmin:
· There are waterproof units available.
E.g. Nuvi 500/550 (I own one), Zumo 550, Zumo 660.
· RAM mounts have dedicated cradles for Garmin units.
http://www.garmin.com.sg/products/ontheroad/
. see below brochure for more pricing info
(prices are based on info available at time of posting, they are always changing)
We would like to have more options but unfortunately, only Garmin units come with weather/water proof capabilities, at least for the time being.
Note that the PND are probably cheaper if bought from Amazon.com (at buyers own risk) and prices are based on info at time of compilation (usually lower at computer shows and promotions). Map view of Garmin PND...
Navigation view of Garmin PND...
Buying from Amazon.com
Apart from buying from local distributors/resellers, Garmin sets are also available from Parallel Importers (e.g. East Gear) or web-shops such as Amazon.com.
For example:
Garmin Nuvi 550 = US$253.58
RAM kit = US$32.86
Total = US286.44 @1.23 approx. S$352.32
(buying the RAM kit from Amazon.com is much cheaper)
Ship both items to a VPost USA address/account, consolidate and ship together to your Singapore home address. For a consolidated package of size 20cm x 20cm x 20cm, weighing 1kg and items valued at US$290, shipping via VPost costs approx. <S$30.
Garmin Nuvi 550 = US$253.58
RAM kit = US$32.86
Total = US286.44 @1.23 approx. S$352.32
(buying the RAM kit from Amazon.com is much cheaper)
Ship both items to a VPost USA address/account, consolidate and ship together to your Singapore home address. For a consolidated package of size 20cm x 20cm x 20cm, weighing 1kg and items valued at US$290, shipping via VPost costs approx. <S$30.
GPS PDN + RAM kit + Shipping approx. <S$390
Note: prices are based on info available at time of posting, they are always changing.
Earlier batches of Holux GPS PND were sold with Papago navigation software while later batches are sold with Galactio V8 Navigation Software. They are preloaded with Singapore Land Authority Singapore map (address data and postal code search capable) and Malfree map for West Malaysia. i.e. owners could obtain free map update from map community MalFreeMap (MFM) as well.
I have visited East Gear's webbie but links for their Holux GPS PND seems to lead to "dead ends".
3D graphics of navigation view...
One thing that some of the Holux GPS PND is capable of but Garmin sets are not is the ability to play music and video files (supports WMA and WMV formats). Nevertheless, I do not need such functions in my GPS navigator so they are "useless" feature to me.
TOMTOM
http://www.tomtom.com/
Founded in 1991, TomTom is listed in 2005 on the Amsterdam Stock Exchange.
Products include portable navigation devices, in-dash infotainment systems, fleet management solutions, maps and real-time services, including the award winning HD Traffic. The company sells its products in over 40 countries and has maps cover 102 countries and territories and 33.2 million kilometers of road across the globe.
In Singapore, TomTom GPS PND products are distributed by Ingram Micro and sold in many retailers such as Challenger, Mustafa, AAAs Com Solutions, Parisilk Electronics, Cyberactive, Song Brothers, etc.
Map: Tele Atlas® map of South East Asia
PAPAGO & WAYWAY
http://www.papago.com.tw/Default.aspx
http://www.m3asia.com/index.php
Papago is another well-known and leading brand in Taiwan manufactured by Maction Technologies, Inc. Commencing June 2009, M3Asia Sdn. Bhd. (M3Asia) has been appointed by Maction Techonologies, Inc as the sole distributor for Papago R Series GPS PND in Malaysia, Indonesia and Thailand. The company is a wholly owned subsidiary of M3 Technologies (Asia) Berhad, a regional mobile content and applications developer, listed on the Malaysian Stock Exchange MESDAQ market.
WayWay GPS PND are designed and distributed by WayWay Innovations (H.K.) Co. Ltd . The sets are preinstalled with the M3GPS navigational software with features such as Junction View, 3D Buildings, Lane Assist, Multi-Route and language support, POI alerts/icons, etc.
In Singapore, Papago/WayWay GPS are distributed by M3Asia Distribution (S) Pte Ltd.
Assisted GPS
(Reference: Wikipedia.org)
Note: prices are based on info available at time of posting, they are always changing.
MARBELLA
http://www.marbella.com.tw
Marbella is a product by Taiwanese company G.SOL Technology Co. which was established in 2002. It's founders comprised of professional engineers and sales team in consumer electronics and telecommunication industries. Marbella GPS PND are distributed by Maka GPS Technologies Group, comprising of Maka GPS Technologies Pte Ltd and Maka GPS Technologies Sdn Bhd.
http://www.marbella.com.tw
Marbella is a product by Taiwanese company G.SOL Technology Co. which was established in 2002. It's founders comprised of professional engineers and sales team in consumer electronics and telecommunication industries. Marbella GPS PND are distributed by Maka GPS Technologies Group, comprising of Maka GPS Technologies Pte Ltd and Maka GPS Technologies Sdn Bhd.
In Singapore, Marbella GPS is distributed by Maka GPS Technologies Pte Ltd.
Marbella PND models commonly sold in Singapore:
Note: prices are based on info available at time of posting, they are always changing.
HOLUX
Marbella PND models commonly sold in Singapore:
Note: prices are based on info available at time of posting, they are always changing.
HOLUX
HOLUX Technology Inc. is a Taiwanese company established in 1994. Current products include automotive, GPS handheld, module, receiver, OEM, and general recreation applications.
Note that East Gear also sells Garmin GPS PND.Earlier batches of Holux GPS PND were sold with Papago navigation software while later batches are sold with Galactio V8 Navigation Software. They are preloaded with Singapore Land Authority Singapore map (address data and postal code search capable) and Malfree map for West Malaysia. i.e. owners could obtain free map update from map community MalFreeMap (MFM) as well.
I have visited East Gear's webbie but links for their Holux GPS PND seems to lead to "dead ends".
Comments
I "owned" a Holux GPSmile NAV-61F (4.3") for a few days before passing it to my brother; since I'm already well served by 2x Garmin sets. The set runs on Windows CE operating system and PAPAGO navigation software so I could only comment on what I have instead of the latest versions of Holux sets running on Galactio.
Basically, the set performed satisfactorily with a reasonably short time to get a fix. In fact, it got a fix faster than my N550 at some locations. Biggest difference from the Garmin maps is the map graphics, in that we were get to see 3D buildings/structures (see screen pic below). Although MFM and MSM are slowly incorporating polygons into their maps, they are nothing close to the 3D graphics. My only concern is whether the nice graphics would "suck" up resources, deteriorating performance of the PND. While the GUI is not as straight forward as that of the Garmin, it does have predictive input function which is a big plus over the Garmin. The set is also "Junction View" capable so basic needs of navigation are said to be more than adequately met. Route calculation is quite fast and was able to bring me to the required places. Feedback from my brother is he had no problem using it for his trip to KL, going places in the city and back. One thing I found lacking is that the Papago software is not able to support Route Planning, i.e. I have to select a saved favourite or a found destination at the start of the navigation. IMO, the ability to plan and save routes in advance is a very useful function that provides lots of convenience and saves lots of time on the road.
3D graphics of navigation view...
TOMTOM
Founded in 1991, TomTom is listed in 2005 on the Amsterdam Stock Exchange.
Products include portable navigation devices, in-dash infotainment systems, fleet management solutions, maps and real-time services, including the award winning HD Traffic. The company sells its products in over 40 countries and has maps cover 102 countries and territories and 33.2 million kilometers of road across the globe.
In Singapore, TomTom GPS PND products are distributed by Ingram Micro and sold in many retailers such as Challenger, Mustafa, AAAs Com Solutions, Parisilk Electronics, Cyberactive, Song Brothers, etc.
Map: Tele Atlas® map of South East Asia
TomTom PND are pre-installed with the latest map of Singapore, Malaysia, Indonesia, Thailand and Brunei.
Map Update Service: 1 Year Map Update Service
Check out TomTom's webbie for the latest PND models:
http://www.tomtom.com/en_sg/products/?WT.Click_Link=top_nav
GO Series
Via Series
The unique thing about TomTom is that they have their navigation application for iPhone/iPad and Android devices. So if you don't want to bring along too many gadgets for your trip, that may be worth considering.
http://www.tomtom.com/en_sg/products/car-navigation/tomtom-navigation-for-iphone-ipad/navigation-app/
http://www.tomtom.com/en_sg/products/car-navigation/tomtom-navigation-for-android/
Comments
I have personally used 2 versions of TomTom PND; a dedicated GPS PND in Australia, a PDA version in Singapore. IMO, the navigation engine is efficient and user experience is very pleasant with simple and straight forward GUI. In some ways, I prefers the on-screen display to that of Garmin but every system/design has their share of pluses and minuses. To use a TomTom PND in Singapore, I have a big concern about its map support; map update service is only free for 1st year and there are no community maps available, unlike Garmin, Papago & Galactio. Although some would say that maps/roads do not change much over just few years, the lack of updated POI is a big minus to me.
Although TomTom does not have watherproof PND like Garmin, some of their PND have dedicated RAM mount cradles available.
RAM Mount Cradles for GPS
TomTom PND models commonly sold in Singapore:
http://www.tomtom.com/en_sg/products/car-navigation/
Map Update Service: 1 Year Map Update Service
Check out TomTom's webbie for the latest PND models:
http://www.tomtom.com/en_sg/products/?WT.Click_Link=top_nav
GO Series
Via SeriesThe unique thing about TomTom is that they have their navigation application for iPhone/iPad and Android devices. So if you don't want to bring along too many gadgets for your trip, that may be worth considering.
http://www.tomtom.com/en_sg/products/car-navigation/tomtom-navigation-for-iphone-ipad/navigation-app/
I have personally used 2 versions of TomTom PND; a dedicated GPS PND in Australia, a PDA version in Singapore. IMO, the navigation engine is efficient and user experience is very pleasant with simple and straight forward GUI. In some ways, I prefers the on-screen display to that of Garmin but every system/design has their share of pluses and minuses. To use a TomTom PND in Singapore, I have a big concern about its map support; map update service is only free for 1st year and there are no community maps available, unlike Garmin, Papago & Galactio. Although some would say that maps/roads do not change much over just few years, the lack of updated POI is a big minus to me.
Although TomTom does not have watherproof PND like Garmin, some of their PND have dedicated RAM mount cradles available.
RAM Mount Cradles for GPS
TomTom PND models commonly sold in Singapore:
http://www.tomtom.com/en_sg/products/car-navigation/
PAPAGO & WAYWAY
http://www.papago.com.tw/Default.aspx
http://www.m3asia.com/index.php
Papago is another well-known and leading brand in Taiwan manufactured by Maction Technologies, Inc. Commencing June 2009, M3Asia Sdn. Bhd. (M3Asia) has been appointed by Maction Techonologies, Inc as the sole distributor for Papago R Series GPS PND in Malaysia, Indonesia and Thailand. The company is a wholly owned subsidiary of M3 Technologies (Asia) Berhad, a regional mobile content and applications developer, listed on the Malaysian Stock Exchange MESDAQ market.
WayWay GPS PND are designed and distributed by WayWay Innovations (H.K.) Co. Ltd . The sets are preinstalled with the M3GPS navigational software with features such as Junction View, 3D Buildings, Lane Assist, Multi-Route and language support, POI alerts/icons, etc.
In Singapore, Papago/WayWay GPS are distributed by M3Asia Distribution (S) Pte Ltd.
http://www.m3asia.com/index.php?option=com_dealers&view=dealers&Itemid=65
Notable dealers are Challenger, Song Brothers, Motec Motor Assessories, etc. and East Gear Pte Ltd is a parallel importer.
Models shown above are mostly with 5" screen and pre-installed with the M3GPS X# and Reality 7 navigation softwares. They come with Lane assist, Junction Views, realistic 3D buildings and landmarks, Multimedia players, improved routing sequence, and some models are equipped with voice activation command, bluetooth and FM Traffic Message Channel (TMC).
Notable dealers are Challenger, Song Brothers, Motec Motor Assessories, etc. and East Gear Pte Ltd is a parallel importer.
Models shown above are mostly with 5" screen and pre-installed with the M3GPS X# and Reality 7 navigation softwares. They come with Lane assist, Junction Views, realistic 3D buildings and landmarks, Multimedia players, improved routing sequence, and some models are equipped with voice activation command, bluetooth and FM Traffic Message Channel (TMC).
Shinco
http://www.shinco.com.sg/pdtCVAS.htm
Shinco was established in 1980. It has 12 manufacturing plants and more than 8,000 employees. It manufactures Portables DVD Player, DVD players, Home Theatre Systems, Micro-Hifi Systems, LCD TV Monitors, GPS, Car Stereo, air-conditioners and washing machines. Shinco products include the high-quality DVD players, Home theaters, portable DVDs and car DVD players, all of them have emerged with multi-series, multi-breed and multi-style.
In Singapore, Shinco GPS are distributed by HC Shinco International Pte Ltd, established in 1990s to distribute its products in SEA region.
Mio
http://www.mio.com/
Sensonic
http://www.sensonic-global.com/GPS.html
Sensonic Global Pte Ltd (Singapore)
http://www.shinco.com.sg/pdtCVAS.htm
Shinco was established in 1980. It has 12 manufacturing plants and more than 8,000 employees. It manufactures Portables DVD Player, DVD players, Home Theatre Systems, Micro-Hifi Systems, LCD TV Monitors, GPS, Car Stereo, air-conditioners and washing machines. Shinco products include the high-quality DVD players, Home theaters, portable DVDs and car DVD players, all of them have emerged with multi-series, multi-breed and multi-style.
In Singapore, Shinco GPS are distributed by HC Shinco International Pte Ltd, established in 1990s to distribute its products in SEA region.
Mio
http://www.mio.com/
Sensonic
http://www.sensonic-global.com/GPS.html
Sensonic Global Pte Ltd (Singapore)
2 Ang Mo Kio Street 64 #02-01, Econ Industrial Building Singapore 569084.
Tel: (65) 6483 9306 Fax: (65) 6483 9307
SITES FOR GPS MAP UPDATES
~ official Garmin Singapore website
~ Free Garmin, Papago and Galactio map for Malaysia, Singapore, Brunei, Indonesia and Thailand
~ Registration/Login is required (free)
~ Note that newer models of Garmin PND (e.g. Nuvi 1460, Nuvi 3790, etc) have some firmware compatibility issue with MFM maps due to use of different map compilers; MFM uses an older version of map compiler. Severity of incompatibility differs from model to model and location.
~ my Nuvi 550 has no issues with MFM or MSM at all, but the newer Nuvi 1460 did have a little issue with MFM with polygons (it hangs when i do long haul routing).
~ Note that newer models of Garmin PND (e.g. Nuvi 1460, Nuvi 3790, etc) have some firmware compatibility issue with MFM maps due to use of different map compilers; MFM uses an older version of map compiler. Severity of incompatibility differs from model to model and location.
~ my Nuvi 550 has no issues with MFM or MSM at all, but the newer Nuvi 1460 did have a little issue with MFM with polygons (it hangs when i do long haul routing).
~ Free Garmin and Mapking maps for Malaysia, Singapore, Brunei
~ Registration/Login is required (free)
~ Registration/Login is required (free)
~ Maps for Shinco, Holux, Marbella, Besta, Mio, etc.
~ Andriod, Windows CE, Windows Mobile, PC, etc.
~ Product registration required
Assisted GPS
(Reference: Wikipedia.org)
Assisted GPS, generally abbreviated as A-GPS or aGPS, is a system which can, under certain conditions, improve the startup performance, or time-to-first-fix (TTFF) of a GPS satellite-based positioning. Unlike standalone/autonomous GPS PND's operations which use radio signals from satellites in orbit, A-GPS uses network resources to locate and utilise the satellites faster as well as better in poor signal conditions, e.g. in congested city where lots of high rise buildings deteriorates satellite signals. In poor signal conditions, satellite signals may suffer multipath propagation where signals bounce off buildings, or are weakened while passing through atmospheric conditions, walls or tree cover. When first turned on under such poor conditions, some standalone GPS PND may not be able to get a fix (current location) due to the fragmentary signal, rendering them unable to function until a clear signal can be received continuously for up to about 12½ minutes (the time needed to download the GPS almanac and ephemeris).
An A-GPS system can address these problems by using data available from a network, through WiFi and/or mobile GPRS/3G network. For billing purposes, network providers often count this as a data access, which can cost money depending on the mobile/data plan subscribed. In other words, GPS uses free for all on-air satellite signals and A-GPS uses data from WiFi and/or payable data downloads over the mobile phones network. So the next time you turn on your mobile phone's GPS, remember to check whether its A-GPS is activated. There are cases where users are "slapped" with a hefty mobile phone bill for "using" A-GPS overseas, data roaming services are very costly.
