A brief description of GPS and its role in Healthcare

1. Colonel Zulfiquer Ahmed Amin
M Phil, MPH, PGD (Health Economics), MBBS
Armed Forces Medical Institute (AFMI)

2. Introduction
Over the years, people have used a variety of techniques to navigate
across the globe. Traditionally, people relied on stars and landmarks
to travel between various locations, while maps and compasses
helped to prevent people from getting lost.
The advent of the Global Positioning System, or ‘GPS’ for short ,
means people no longer have to rely on these traditional (and often
complex and inaccurate) positioning techniques to find their way
around.

3. What is GPS?
GPS, which stands for ‘Global Positioning System’
GPS is the only system today able to show our exact position on
the Earth
- anytime,
- in any weather,
- anywhere.
Definition: GPS is a positioning system based on a constellation of
satellites that continuously transmit coded information. The
information transmitted from the satellites can be interpreted by
receivers to precisely identify locations on earth by measuring
distances from the satellites.

4. Characteristics of GPS
• Accurate (Precise)
Almost!
• Free
• Reliable
• All weather
• Anytime & anywhere
•Unlimited user capacity
● Accurate to 21 meters 95% of time

5. Common use of GPS
• GIS data collection, Surveying
& mapping
• Navigation
• Recreation
• Police and Emergency Medical
Services
• Firefighters
• Map makers
• Science
• Environmental Stewardship
• Construction & Mining
• Aviation Benefit
• Disaster Management
• Epidemiological investigation
of disease outbreak/ epidemic
• Heli-evacuation of emergency
patients
Geographic Information System (GIS) is a system designed to capture, store, manipulate,
analyze, manage, and present geographic data.

7. Segments of GPS
Source:Trimble
1. Space Segment: A constellation of satellites.
2. Control Segment (For USA): A network of earth-based facilities. 6
ground stations located around the world, maintaining proper sat
functioning.
3. User Segment: All of us with receivers, phones, etc.

9. • They are constantly moving, making two complete orbits in less
than 24 hours.
• These satellites are travelling at speeds of roughly 7,000 miles an
hour.
• GPS satellites are powered by solar energy. They have backup
batteries onboard to keep them running in the event of a solar
eclipse, when there's no solar power.
• GPS works in any weather conditions, anywhere in the world, 24
hours a day.
• There are no subscription fees or setup charges to use GPS.

10. • Each satellite is built to last about 10 years. Replacements are
constantly being built and launched into orbit.
• A GPS satellite weighs approximately 2,000 pounds and is about
17 feet across with the solar panels extended.
• Transmitter power is only 50 Watts or less.
• Worldwide coverage
• Gives information on Latitude/Longitude/Height
• Can provide centimeter to 5-meter accuracy in seconds

11. Source:Trimble
US GPS
NAVigation System Timing And Ranging (NAVSTAR)
Created by the U. S. Department of Defense (DOD) to provide
navigation, location, and timing information for military operations.
24 Operational satellites (6 spares)
Orbiting at 22,000 km altitude
6 different orbital planes each with 4 satellites

12. Russian GPS
Global’naya Navigatsionnaya Sputnikovaya Sistema (GLONASS)
24 Operational satellites
Orbiting at 19,100 km altitude
3 different orbital planes each with 8 satellites
Indian GPS
Indian Regional Navigational Satellite System (IRNSS)
7 satellites
Operational (2011-2013)
Orbiting at 24,000 km altitude

13. European GPS
GALILEO constellation (EU & ESA)
Operational (2014-2019)
Provides a global SAR (Search and Rescue) capability;
Each satellite equipped with transponders to relay distress signals to
SAR coordinators and then back to the user
30 planned satellites in orbit with 3 spares
Orbits at 23,222 km altitude

14. Other Countries Developing GPS
COMPASS (a.k.a. Beidou-2, BIG DOPPLER, or BD2)
Chinese GPS constellation
5 satellites operational; 30 more planned
DORIS (Doppler Orbitography and Radio-positioning
Integrated by Satellite)
French precision NAV system
QZSS, (Quasi-Zenith Satellite System)
Japan’s 3 satellite regional time transfer GPS system

15. GPS Control Segment
The GPS Ground Segment (also referred to as Control Segment or
Operational Control System) is the responsible for the proper
operation of the GPS system.
The GPS Control Segment is composed by a network of Monitor
Stations (MS), a Master Control Station (MCS), a backup of the MCS
and the Ground Antennas (GA).

16. Control Segment
The GPS Ground Segment (also referred to as Control Segment or
Operational Control System) is the responsible for the proper
operation of the GPS system.
Consists of:
● Master Control Station (MCS)
● Alternate MCS
● 4 dedicated ground antennas
● 6 dedicated monitor stations
- Falcon AFB (Colorado)
- Hawaii
- Cape Canaveral
- Ascension Island
- Diego Garcia
- Kwajalein Atoll

17. GPS Monitoring/ Control Station
The Monitor Stations network comprised six sites located in:
1. Hawaii,
2. Colorado Springs (Colorado, US),
3. Ascension Island (South Atlantic),
4. Diego Garcia (Indian Ocean),
5. Kwajalein (North Pacific).
6. Cape Canaveral
Six additional monitoring stations were added in 2005 in Argentina,
Bahrain, United Kingdom, Ecuador, Washington DC, and
Australia.
Each of the monitor stations checks the exact altitude, position,
speed, and overall health of the orbiting satellites.

18. The Master Control Station (MCS) processes the measurements
received by the Monitor Stations (MS) to estimate satellite orbits
and clock errors, among other parameters, and to generate the
navigation message. These corrections and the navigation message
are uploaded to the satellites through the Ground Antennas, which
are co-located in four of the Monitor stations (Ascension Island,
Cape Canaveral, Diego Garcia, and Kwajalein).

19. User Segment
Source:Trimble
•Software
•User
•Receivers

20. History (USA)
• GPS was originally intended for military applications during Cold War for
missile (ICBMs) defense
• The first satellite navigation system, used by the United States Navy, was
first successfully tested in 1960 (Using a constellation of five satellites).
• It can take out enemy missiles/silos with precision
• 1972- Flight tests of GPS
• 1978-1989, 11 satellites launched
• 1990-91, 1st GPS used in war (Gulf War-1)
• 1993: The GPS system became fully operational
• on 8 December 1993 when the full constellation of 24 satellites, 21
operational and three in reserve, became available.
• 1996, President Clinton declares GPS for duel use (Both for military and
civil).
• 2004 (Nov), Qualcom announces “assisted GPS” for use in mobile phones

21. GPS is a location system based on a constellation of 24 satellites
orbiting the earth at altitude of approximately 20,200 km
(12,550 miles).
Each satellite circles the Earth twice a day.
And transmit signal information to earth
GPS receivers take this information and use triangulation to
calculate the user's exact location
How GPS works?

22. How GPS works?
• 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).

23. Primary function of GPS is to find out the distance of device from the
satellite.

24. Finding the distance of the device from the satellite is done by the
principle of ‘Triangulation’

25. What is triangulation?
The first sign tells us that we are 740 km from Adelaide . This fact
alone isn’t particularly useful, as we could be anywhere on a circle
around Adelaide that has a radius of 740 km.
The second sign informs us that we are also 1,500 km from Cairns. If
we combine these two facts, we can limit our location to one of two
possibilities (A or B, shown by the intersection of the two circles).
The third sign also tells us that we are 1,430 km from Sydney. Using
this final bit of information, we can quickly determine that we are at
Location A -Lake Eyre in South Australia.

26. Triangulation

30. How accurate is GPS?
Today's GPS receivers are extremely accurate.
Certain atmospheric factors and other sources of error can affect the
accuracy of GPS receivers.

31. Clock Errors.
The ability of a GPS receiver to determine a fix, depends on its ability
to determine how long it takes a signal to get from the satellite to
the receiver antenna. This requires that the clocks in the satellite be
synchronized. Even a small amount of difference in the clocks can
make large differences in the distance measurements.
Ephemeris Errors.
The receiver expects each satellite to be at a certain place at a
particular given time. Every hour or so, in its data message, the
satellite tells the receiver where it is predicted to be at a time “t”
hence. If this ephemeris prediction is incorrect, and the satellite not
where it is predicted to be, then the measurement of the range from
the receiver antenna to the satellite will be incorrect.

32. Receiver Errors.
The receiver cannot exactly measure and compute the distance to
each satellite simultaneously. The computer in the receiver works
with a fixed number of digits and is therefore subject to calculation
and rounding errors.
Selective Availability.
- Intentional degradation of GPS accuracy
- 100m in horizontal and 160m in vertical
- Accounted for most error in standard GPS
- Turned off from May 2, 2000

33. Atmospheric Errors
For most of its trip from the satellite to the receiver antenna, the
GPS signal travels through the virtual vacuum of “empty space”. Half
of the mass of the earth’s atmosphere is within the first 3.5 miles of
the surface. Virtually all of it lies within the first 100 miles of the
surface. This means that the signal gets to go the speed of light for
more than 19,000 of its 20,000 kilometer trip. When it gets to the
earth’s atmosphere, however, the speed drops by an amount that
varies somewhat randomly. This small change in speed induces a
small error in distance and therefore errors in position (about 4
meters). These errors from the ionosphere are primarily from
charged particles under the influence of the earth’s magnetic field.
More sophisticated GPS units are able to calculate and remove the
effects of the ionosphere. The troposphere, the denser atmosphere
closer to the earth, generates error primarily due to changes in
atmospheric pressure and depth.

34. Methods of Positioning
(How to enhance accuracy of reading)
• Autonomous (Least accurate)
• Differential (Mid-level accuracy)
• Phase Differential (Most accurate)

35. Autonomous Positioning (Navigated/ GPS point-
positioning)
GPS point positioning, also known as standalone or autonomous
positioning, involves only one GPS receiver. That is, one GPS
receiver simultaneously tracks four or more GPS satellites to
determine its own coordinates with respect to the center of the
Earth.
• No corrections are applied to locations
• Locations off by as much as 100 m if SA (Selective Availability) is
active
• Locations off by as much as 5-6 m if SA not active
• Accuracy depends on degree of Selective Availability (How much
is Falcon AFB distorting the signals)
• Other errors also influence the reading.

36. Differential GPS: Post Processing
• Corrections are applied to positions after returning from field.
• Uses data collected simultaneously by a base station.
• Gives sub-meter to 5 meter accuracy.

37. Differential Correction: Real -Time
• Correction is applied while still in the field.
• Makes use of additional signals being broadcast by a known
ground station.

38. Phase Differential Correction
• To achieve higher accuracies (cm-mm scales)
• Eliminates effects of both clock and atmospheric errors.

39. WEAKNESSES of GPS
• The technology is very power hungry, most systems will only last 8-
12 hours before needing a battery replacement or recharge.
• The GPS signal is unable to pass through solid structures so is
unable to work indoors, underground, under the water, or under a
dense canopy of trees.
• Can be affected by large buildings and is typically unreliable in CBD
areas.
• GPS accuracy is related to the quality of signal reception, the larger
the antenna the better the signal – so absolute miniaturization is not
possible whilst maintaining good positioning accuracy.

40. US Space-Based PNT (Position, Navigation & Timing) Org

41. Bangabandhu Satellite-1
The Bangabandhu Satellite-1 (BS-1) is the first Bangladeshi
geostationary communications and Broadcasting Satellite. It was
launched on May 11, 2018. The project is being implemented by
Bangladesh Telecommunication Regulatory Commission (BTRC).
Bangabandhu satellite-1's launch station was Kennedy Space Center
on Merritt Island, Florida, USA and ground control station is in
Betbunia, and Gazipur.
The satellite is expected to be located at the 119.1° East longitude
geostationary slot. The total cost of the satellite was projected to be
248 million US dollars in 2015 (Tk 19.51 billion), financed via a $188.7
million loan from HSBC Holdings plc.

42. Bangabandhu Satellite-1 carries a total of 40 Ku-band (Ku-band
service operates in the 12 to 18 GHz frequency range resilient to
tropical rain, and suitable for maritime and aeronautical based
communications) and C-band (C-band service is used for a wide
range of government communications, including battlefield
communications, command and control systems, as well as disaster
recovery. Operating in the 4 to 8 GHz frequency range, C-band
satellite coverage is ideal for intercontinental and global
communications over land and sea) transponders with a capacity of
1600 megahertz and a predicted life span to exceed 15 years. The
satellite will expand coverage over all of Bangladesh and its nearby
waters including the Bay of Bengal, India, Nepal, Bhutan, Sri Lanka,
the Philippines, and Indonesia.

43. Location of Bangabandhu-1 Satellite

44. Use of GPS in Healthcare
1. Faster Response Time
GPS technology has helped streamline the process of finding
accident victims at precise geographic locations, i.e. along a road,
etc. Thus shaving off precious minutes in which an injury might
become fatal.
2. Alzheimer's & Mentally Unstable
Placing some sort of GPS tracking device on patients is incredibly
useful for knowing the whereabouts of patients who are likely to
attempt to go missing, escape, wander off and not receive the care
they require.
3. Communications’ satellites enable long-distance telephone or
digital communications on Earth in places where there is no
telephone infrastructure.

45. 4. Evaluating patient recovery following surgery.
The patients carry a GPS unit with them after the operation, tracking
their movements, which are then analyzed. Future development will
integrate additional sensors that will allow the combination of GPS
data with physiological data, such as heart rate and blood pressure.
5. Epidemiological Surveillance
For tracking a particular disease pattern among the community
members for effective planning for prevention and control.
6. Heli-evacuation of emergency patients
To find out location of both patients and hospitals, GPS can be used.
7. Remote sensing technology.
To look at environmental factors for disease, such as water
temperature, the air, the type of soil.

46. 8. Telemedicine or tele-health, which can be used in remote locations
and can link health experts with other health professionals or
patients anywhere in the world via satellite communications.
9. Earth observation satellites, to analyze the light that bounces off
the Earth and thus analyze the land, air or sea. For example, this
technology can help measure the wind, clouds or rain or other
environmental parameters that are associated with the presence of
insects that can carry diseases. This technology can also help us
measure the extent a region is affected by drought or flooding and
be used for the assessment of food supply or potential for water-
borne diseases.
10. GPS that is used in mobile phone technology – can also be used
to investigate outbreaks. GPS technology can also pinpoint the
location of a suspected source of contamination.

47. GPS in Healthcare