Global Positioning System - Working

Global Positioning System - Working
GPS system says the location of any object on earth. We hear about GPS mobile phones, but what is a GPS? and How it is functioning? I would like to share the basics and working of a GPS here.

GPS Working (Picture from: Google images)

INTRODUCTION

The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS provides specially coded satellite signals that can be processed in a GPS receiver, enabling the receiver to compute position, velocity and time. GPS essentially consists of three segments namely Space segment, Control Segment and User Segment.

SPACE SEGMENT

The Space Segment of the system consists of the GPS satellites. These Space Vehicles (SVs) send radio signals from space. 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 SVs 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 SVs visible from any point on the earth.

CONTROL SEGMENT

The Control Segment consists of a system of tracking stations located around the world. The Master Control facility is located at Schriever Air Force Base (formerly Falcon AFB) in Colorado. These monitor stations measure signals from the SVs which are incorporated into orbital models for each satellites. The models compute precise orbital data (ephemeris) and SV clock corrections for each satellite. The Master Control station uploads ephemeris and clock data to the SVs. The SVs then send subsets of the orbital ephemeris data to GPS receivers over radio signals.

USER SEGMENT

The GPS User Segment consists of the GPS receivers and the user community. GPS receivers convert SV signals into position, velocity, and time estimates. Four satellites are required to compute the four dimensions of X, Y, Z (position) and Time. GPS receivers are used for navigation, positioning, time dissemination, and other research. Navigation in three dimensions is the primary function of GPS. Navigation receivers are made for aircraft, ships, ground vehicles, and for hand carrying by individuals

WORKING

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. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it [2].

A GPS receiver must be locked on to the signal of at least three satellites to calculate a 2D position (latitude and longitude) and track movement. With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude). Once the user's position has been determined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time and more.

SIGNALS

The SVs transmit two microwave carrier signals. The L1 frequency (1575.42 MHz) carries the navigation message and the SPS code signals. The L2 frequency (1227.60 MHz) is used to measure the ionospheric delay by PPS equipped receivers. The signals travel by line of sight, meaning they will pass through clouds, glass and plastic but will not go through most solid objects such as buildings and mountains.

A GPS signal contains three different bits of information — a pseudorandom code, ephemeris data and almanac data. The pseudorandom code is simply an I.D. code that identifies which satellite is transmitting information. Ephemeris data tells the GPS receiver where each GPS satellite should be at any time throughout the day. Each satellite transmits ephemeris data showing the orbital information for that satellite and for every other satellite in the system. Almanac data, which is constantly transmitted by each satellite, contains important information about the status of the satellite (healthy or unhealthy), current date and time. This part of the signal is essential for determining a position.

Systems, Control Systems and Classifications

Systems, Control Systems and Classifications

System: A system comprises of several component work together for a specific task
Control System: If the output is of our desire and able to control, then the system is called as Control systems

General Classification of systems:

1.  Open loop System: In an Open loop System, the control action is independent of the desired output.

OR
When  the output quantity of  the control system  is not  fed back  to  the  input quantity,  the control system is called an Open loop System. e.g. Blind man's action, traffic control without traffic police

2.  Closed loop System: In the Closed  loop Control System the control action is dependent on the desired output, where the output quantity is considerably controlled by sending a command signal to input quantity. The closed loop systems are normally have feed back.
e.g Normal man's action, Automobile systems, traffic signal control with traffic police etc.

Based on the type of system, control systems can be classified as
1.Electrical System,
2. Mechanical System (Translational, Rotational)
3. Hydraulic system
4. Pneumatic systems
5. Thermal systems and so on.

SECURITY ISSUES in SCADA based system

SECURITY ISSUES in SCADA based systems

The move from proprietary technologies to more standardized and open solutions together with the increased number of connections between SCADA systems and office networks and the Internet has made them more vulnerable to attacks - see references. Consequently, the security of SCADA-based systems has come into question as they are increasingly seen as extremely vulnerable to cyberwarfare/cyberterrorism attacks

SCADA systems are used to control and monitor physical processes, examples of which are electrical SCADA system would cause financial losses to all the customers that received electricity from that source. How security will affect legacy SCADA and new deployments remains to be seen. transmission of electricity, transportation of gas and oil in pipelines, water distribution, traffic lights, and other systems used as the basis of modern society. The security of these SCADA systems is important because compromise or destruction of these systems would impact multiple areas of society far removed from the original compromise. For example, a blackout caused by a compromised

There are two distinct threats to a modern SCADA system. First is the threat of unauthorized access to the control software, whether it be human access or changes induced intentionally or accidentally by virus infections and other software threats residing on the control host machine. Second is the threat of packet access to the network segments hosting SCADA devices. In many cases, there is rudimentary or no security on the actual packet control protocol, so anyone who can send packets to the SCADA device can control it. In many cases SCADA users assume that a VPN is sufficient protection and are unaware that physical access to SCADA-related network jacks and switches provides the ability to totally bypass all security on the control software and fully control those SCADA networks. These kinds of physical access attacks bypass firewall and VPN security and are best addressed by endpoint-to-endpoint authentication and authorization such as are commonly provided in the non-SCADA world by in-device SSL or other cryptographic techniques.

Many vendors of SCADA and control products have begun to address these risks in a basic sense by developing lines of specialized industrial firewall and VPN solutions for TCP/IP-based SCADA networks. Additionally, application white listing solutions are being implemented because of their ability to prevent malware and unauthorized application changes without the performance impacts of traditional antivirus scans Also, the ISA Security Compliance Institute (ISCI) is emerging to formalize SCADA security testing starting as soon as 2009. ISCI is conceptually similar to private testing and certification that has been performed by vendors since 2007. Eventually, standards being defined by ISA99 WG4 will supersede the initial industry consortia efforts, but probably not before 2011 .

The increased interest in SCADA vulnerabilities has resulted in vulnerability researchers discovering vulnerabilities in commercial SCADA software and more general offensive SCADA techniques presented to the general security community. In electric and gas utility SCADA systems, the vulnerability of the large installed base of wired and wireless serial communications links is addressed in some cases by applying bump-in-the-wire devices that employ authentication and Advanced Encryption Standard encryption rather than replacing all existing nodes.

Innovative revolutions in Credit card technologies

Technology updates on Credit cards

The credits cards are normally built with a magnetic strip which upon swiping at ATM or shopping centre will enable transactions. In the conventional cards, there is no facility of display card balance and keypads so on. There are many complaints from card holders of losing their money without their knowledge. This is mainly by the criminals who steal the data of the card using magnetic strip reader or noting down the card details, even cloning of the cards. To overcome these problems and completely preventing the theft or fraud, innovative revolution in the credit card technologies have emerged, some of the key technologies are addressed here.

Credit card with miniature display and keypads

The innovative technology has opened new windows for credit cards with display and keypad features. In these novel cards, the card is embedded with display and keypads so that the users can interact with them. This Credit card embedded authentication device can even provide additional security to prevent bank frauds for the users. These cards feature to display the current balance of the clients. Some card uses a one time pass code to authorize the online and phone transactions. These cards normally have built in batteries which will last for about 4 to 5 years. These programmable credit or master cards has yet to popularize the world for the cashless transactions.

Multi account and dynamic credit cards:

In this, we can store details of many cards and use any one card by choosing the magnetic strip of a particular card. This card also built in with a eInk display which consumes less power and no power if not displaying anything.

The dynamic cards are automatic reprogrammable magnetic strip where we can toggle between strips by using buttons and hide & show the desired credit card numbers with display facilities.

Credit card swipe phone or i-phone:

These phones are built with credit card reader facility where the entire transactions are done with phone. This is mainly useful for those doing micro finance and small business. The reader can be easily plugged into the audio jack. While swiping with this reader, the authentication is done with the mobile phone display.

The Braille Credit Card :

The Braille card specially designed to handle a visually challenged person to know the amount of money that has been charged on their card. The card with its Braille display features the Braille to know the sum that is needed to pay. The card also has an inbuilt miniature speaker which reads aloud the figures for further assistance. This special card can also be used by old aged people who suffer from poor eyesight with the features of built in speakers.