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Welcome to GPS Hacks. This site is not about hacking a GPS but everything you want to know about GPS including General information, GPS reviews, Tutorials, GPS How-to and much more. If you want to contribute this site please feel free to Contact us. What is GPS? GPS (Global Positioning System) is a "constellation" of 24 well-spaced satellites that orbit the Earth and make it possible for people with ground receivers to pinpoint their geographic location. How GPS Works GPS system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the user's exact location.

GPS Jamming

It is possible to jam  GPS nevigation system. The jamming techniques is to limit the effectiveness of an opponent’s communications and/or detection equipment. There are several case, intentional or unintentional, has been recorded including Air Force conducted GPS jamming exercises in 2003. There is also a detailed description of how to build a short range GPS L1 C/A jammer was published in Phrack issue 60 by an anonymous author.

If stronger signals were generated intentionally, they could potentially interfere with aviation GPS receivers within line of sight. Also GPS signals can also be interfered with by natural geomagnetic storms, predominantly at high latitudes. There is a feature called Receiver Autonomous Integrity Monitoring(RAIM) is designed to provide a warning to the user if jamming or another problem is detected. Some aviation and marine receivers usually use this kind of featured in their GPS system.

GPS jamming is specially important since many modern weapon such as GPS-guided bomb use GPS. The U.S. government believes that such jammers were also used occasionally during the 2001 war in Afghanistan.
But there are many people believe that GPS jammer is not effective. Regardless it is effective or not, it is an important uspect of GPS user and everyone should be aware of it.

GPS Mapping – GPS Mapping Softwares – GPS Mapping PDA Software – Free GPS Mapping Softwares

What is GPS mapping?

Mapping is the process of map making. Maps function as visualization tools for spatial data. Spatial data is acquired from measurement and can be stored in a database, from which it can be extracted for a variety of purposes.

GPS , stands for Global Positioning System, is the fully-functional satellite navigation system. A constellation of more than two dozen GPS satellites broadcasts precise timing signals by radio, allowing any GPS receiver to accurately determine its location (longitude, latitude, and altitude) in any weather, day or night, anywhere on Earth.

A GPS collected spatial information does not make much sense until it it is plot on a map. This precess known as GPSMapping . There are various techniques and methods can be used to plot GPS data on map. Also there are many software available to map GPS information. There are verity of application of GPS Mapping .


– GPS Mapping Softwares
– GPS Mapping PDA Software r
– Free GPS Mapping Software
– Free GPS Mapping PC Pocket
– GPS Mapping Service
– GPS laptop mapping software
– GPS Mapping System
– GPS Handheld Mapping

How accurate is GPS?

The accuracy that can be achieved using GPS depends on the type of equipment used, the time of observation, and the positions of the satellites being used to compute positions. In general, recreational and mapping grade receivers using C/A code without differential correction are accurate to between 5 and 15 meters. Many people using recreational grade receivers don’t realize they cannot get highly accurate readings using them autonomously (without differential correction).

Most mapping and recreational grade receivers with differential correction can provide from about 1 to 5 meter accuracy. Some receivers use what is called “carrier-smoothed code” to increase the accuracy of the C/A code. This involves measuring the distance from the receiver to the satellites by counting the number of waves that carry the C/A code signal. These receivers can achieve 10 cm to 1 meter accuracy with differential correction. Dual frequency survey grade receivers using more advanced network survey techniques can achieve centimeter to millimeter accuracy.

Some people wonder why GPS is better than Loran or other systems that use ground-based transmitters. The accuracy of ground-based location systems such as Loran, which uses low frequency radio signals, is affected by signal distortion, varied terrain, local atmospheric disturbances and limited coverage. Since GPS signals come from satellites, the problems common to ground-based systems can be avoided.

What Should you Know Before Purchasing a GPS Receiver?

Before investing in GPS equipment, it is important to clearly define your needs in terms of accuracy level required and end results expected. Do you simply want to be able to navigate in the woods, or do you want to map out points, lines and areas that can be differentially corrected and imported into a GIS (a computer mapping system)? Do you need real-time differential GPS for any reason?

Is 15 meter accuracy good enough? If so, you don’t have to worry about differential correction. If you want to make a map from your data, is 1-5 meter accuracy sufficient, or do you need sub-meter accuracy for your application? Remember that more accurate equipment is more expensive. If you decide you need high accuracy, be sure you can justify the added expense.

In addition, consider your needs for durability and weather resistance, and details such as whether or not an external antenna can be connected to the receiver, and its size, weight and suitability for your method of survey (e.g., will it be used in a backpack, mounted on a vehicle, or carried in your hand?).

Identifying your requirements ahead of time will help you determine which type of receiver to purchase, and specific features you will need in order to accomplish your objectives. It will help you avoid purchasing a receiver that you will be disappointed with later because it can’t perform the way you expect it to. A good strategy is to clearly outline your project requirements and then contact several GPS equipment manufacturers with your specifications. As you research available equipment and ask questions, you will gain an understanding of what kinds of equipment are currently available and will meet your needs.

GPS Error – Sources of GPS Error – GPS Error Analysis

There are many sources of possible errors that will degrade the accuracy of positions computed by a GPS receiver. The travel time of GPS satellite signals can be altered by atmospheric effects; when a GPS signal passes through the ionosphere and troposphere it is refracted, causing the speed of the signal to be different from the speed of a GPS signal in space. Sunspot activity also causes interference with GPS signals. Another source of error is measurement noise, or distortion of the signal caused by electrical interference or errors inherent in the GPS receiver itself. Errors in the ephemeris data (the information about satellite orbits) will also cause errors in computed positions, because the satellites weren’t really where the GPS receiver “thought” they were (based on the information it received) when it computed the positions. Small variations in the atomic clocks (clock drift) on board the satellites can translate to large position errors; a clock error of 1 nanosecond translates to 1 foot or .3 meters user error on the ground. Multipath effects arise when signals transmitted from the satellites bounce off a reflective surface before getting to the receiver antenna. When this happens, the receiver gets the signal in straight line path as well as delayed path (multiple paths). The effect is similar to a ghost or double image on a TV set.

Geometric Dilution of Precision (GDOP)
Satellite geometry can also affect the accuracy of GPS positioning. This effect is called Geometric Dilution of Precision (GDOP). GDOP refers to where the satellites are in relation to one another, and is a measure of the quality of the satellite configuration. It can magnify or lessen other GPS errors. In general, the wider the angle between satellites, the better the measurement (see GPS Basics slide show for an illustration). Most GPS receivers select the satellite constellation that will give the least uncertainty, the best satellite geometry.

GPS receivers usually report the quality of satellite geometry in terms of Position Dilution of Precision, or PDOP. PDOP refers to horizontal (HDOP) and vertical (VDOP) measurements (latitude, longitude and altitude). You can check the quality of the satellite configuration your receiver is currently using by looking at the PDOP value. A low DOP indicates a higher probability of accuracy, and a high DOP indicates a lower probability of accuracy. A PDOP of 4 or less is excellent, a PDOP between 5 AND 8 is acceptable, and a PDOP of 9 or greater is poor. Another term you may encounter is TDOP, or Time Dilution of Precision. TDOP refers to satellite clock offset. On a GPS receiver you can set a parameter known as the PDOP mask. This will cause the receiver to ignore satellite configurations that have a PDOP higher than the limit you specify.

Selective Availability (SA)
Selective Availability, or SA, occurred when the DoD intentionally degraded the accuracy of GPS signals by introducing artificial clock and ephemeris errors. When SA was implemented, it was the largest component of GPS error, causing error of up to 100 meters. SA is a component of the Standard Positioning Service (SPS), which was formally implemented on March 25, 1990, and was intended to protect national defense. SA was turned off on May 1, 2000.

Following Table lists the possible sources of GPS error and their general impact on positioning accuracy:

Table – GPS Error Budget

Error source Potential error Typical error
Ionosphere 5.0 meters 0.4 meters
Troposphere 0.5 meters 0.2 meters
Ephemeris data 2.5 meters 0 meters
Satellite clock drift 1.5 meters 0 meters
Multipath 0.6 meters 0.6 meters
Measurement noise 0.3 meters 0.3 meters
Total ~15 meters ~10 meters

Free GPS Software

There are many GPS free software you can use with your GPS unit. Most of the software you can download from internet and use it right way. Here is a list of free software:

1. amAze :
Web Address:
Description: This is GPS navigation for your mobile phone. It covers the US and 15 European countries. This is a java based software which enable you to Search and navigate to businesses listed in yellow pages directories.

2. Automatic Position Reporting System (APRS)
Web Address:
Description: APRSâ„¢ is a multifaceted system for use with packet radio by Hams, it allows the monitoring of real time geographical information such as the position of vehicles, the status of weather, radio direction finding and much much more. It envolves mapping, GPS tracking, packet radio, etc. It is a VERY interesting facet of packet radio and has much to offer most everyone including non-hams that just want to watch over the internet.

3. Async & RINEX :
Web Download Address:
Description: Helps Obtaining raw data from some Garmin units.

4. Cetus GPS:
Web Address:
Description: Cetus GPS is the Swiss Army Knife of GPS tracking and field data collection. It is intended for use by GIS surveyors, scientists, explorers and GPS enthusiasts who need to extend the features of their standard GPS equipment.

5. Cotogps :
Web Address:
Description: GPS program for Palm Powered Devices. It shows all important information and serves well on my Geocaching tours.

Web Address:
Description: A system to send DGPS corrections over the Internet.

7. DNR Garmin Application :
Web Address:
Description: This software was built to provide users the ability to directly transfer data between Garmin GPS handheld receivers and various GIS software packages.

8. Earthcomber :
Web Address:
Description: This software supports Palm, Windows Mobile Pocket PC and Smartphone and allows users to specify types of restaurants, shops, ATMs, hotels, landmarks and plot them on a map. It also has free maps for any city and county in the USA.

9. EasyGPS :
Web Address:
EasyGPS is the fast and easy way to transfer waypoints, routes, and tracks between your computer and your Garmin, Magellan, or Lowrance GPS.

10. flexGPS – demo version :
Web Address:
Description: FlexGPS enables the manipulation of maps used with a GPS Receiver.

11. G3 project :
Web Address:
Description: You can use this software with any Java-capable mobile phone connected to a GPS receiver and perform tracking, archiving and geotagging features, with the help of Google Maps and Google Earth.

12. G3 project : G7ToWin
Web Address:
Description: G7ToWin is designed to transfer data between Garmin, Magellan, or Lowrance/Eagle GPS units and a PC.

13. G3 project : Gar2rnx
Web Address:
Description: It use to botain raw data from some Garmin units

14. G3 project : Garmap CE version 1.78
Web Address:
Description: Garmap CE runs on H/PCs or P/PCs running Windows CE 2.0

15. G3 project : Garmap Win
Web Address:
Description: Garmap Win runs on Windows 95/98 or Windows NT 4.0. Garmap Win communicates with Garmin GPS receivers to deal with Track logs, Waypoints and Routes. It has the
following features.

16. G3 project :GEO/GARNIX
Web Address:
Description: GEO is a scriptable coordinate conversion tool that converts lon/lat, ECEF und TM (Gauss-Krüger) coordinate systems.

17. G3 project : GarPsi5
Web Address:
Description: These free GPS software programs allow you to transfer Garmin data onto your Psion models 3a/c/mx or 5.

18. G3 project : GEOsnapper
Web Address:
Description: GEOsnapper geo-tags your photos to make them searchable by location.

19. G3 project : GPilotS

Web Address:
Description: GPilotS allows your PalmPilot to transfer waypoints, routes, and tracks to and from selected Garmin receivers.

20. G3 project : GPS3D
Web Address:
Description: GPS3D is a suite of free GPS software utilities to control a handheld GPS receiver from your PC and see the result in 3D. If you don’t have a GPS receiver you can use GPS3D to see MapBlast maps in 3D and also interact with a 3D representation of Earth.

21. G3 project : GpsActionReplay
Web Address:
Description: GpsActionReplay (GpsAR) is a software that enables replays and performance analysis from GPS data

22. G3 project : GPSBabel
Web Address:
Description: GPSBabel converts waypoints, tracks, and routes from one format to another, whether that format is a common mapping format like Delorme, Streets and Trips, or even a serial or USB upload or download to a GPS receiver such as those from Garmin and Magellan.

23. G3 project : GPSCommunicator

Web Address:
Description: GPSCommunicator is a FREE utility to visually represent NMEA GPS position data in realtime. It works with NMEA 0183 GPS receivers connected via a serial port.

24. G3 project : NMEASleuth
Web Address:
Description: NMEASleuth is a FREE utility to inspect NMEA data streams from devices connected via a serial port.

25. G3 project : GPSCookie
Web Address:
Description: A2B has its own free GPS companion software, GPSCookie, available for Windows and also for PDAs running MS Pocket PC OS.

Child GPS Tracking – GPS Tracking System for Child

A GPS tracking unit is a device that uses the GPS to determine the precise location of a vehicle, person, or other asset to which it is attached and to record the position of the asset at regular intervals. The recorded location data can be stored within the tracking unit, or it may be transmitted to a central location data base, or internet-connected computer, using a cellular (GPRS), radio, or satellite modem embedded in the unit. This allows the asset’s location to be displayed against a map backdrop either in real-time or when analysing the track later, using customized software.

The same system can be used as a GPS Child Locator, which is a lightweight device that attaches to your child’s shoelaces and is designed to help parents or guardians keep track of their children. The device alleviates the stress and panic that ensue when children get lost, or are difficult to reach. It emits a series of loud beeps, allowing parents to find their children quickly and easily. This is also an ideal solution for disabled adults, the elderly and daycare centers.

There are many way you can use GPS technology to track you child. Such as:

  • GPS Real Time Tracking Systems ideal for monitoring the whereabouts of teen drivers enables you to log on to the Internet and see where your child is at any moment. There have been attempts to develop a Real Time GPS Unit the size of a wristwatch for children, but so far battery life and other issues have made this system unreliable. An example of this system is TrimTracXS.
  • GPS Logging Devices will tell you where your child has been after you download the data collected on the GPS Logger to your PC to view the maps and data. one of such systme is PocketTrack.