Group3 - Revision history

GPS-3: Marc David

2008-03-03T22:05:50Z

Marc David

GPS-3 at 21:05, 3 March 2008

2008-03-03T21:05:28Z

GPS-3 at 21:01, 3 March 2008

2008-03-03T21:01:04Z

GPS-3: /* Varieties of GPS devices */ Tim Kope

2008-03-03T20:58:50Z

Varieties of GPS devices: Tim Kope

GPS-3: Marc David

2008-03-03T20:54:06Z

Marc David

GPS-3: /* How the GPS Navigational System Works */

2008-03-03T20:51:53Z

How the GPS Navigational System Works

GPS-3: /* Varieties of GPS devices */

2008-03-03T20:51:30Z

Varieties of GPS devices

GPS-3: Marc David

2008-03-03T20:51:00Z

Marc David

GPS-3: Tim Kope

2008-03-03T20:46:32Z

Tim Kope

GPS-3: Marc David

2008-03-03T20:39:04Z

Marc David

@@ Line 12: / Line 12: @@
 ==How the GPS Navigational System Works==
-[[Image:http://upload.wikimedia.org/wikipedia/commons/6/6f/Trilateration.png|thumb|right|200px]]
 GPS, or global positioning system, is a system of satellites, computers, and receivers that can determine the latitude, longitude, and altitude of a receiver located on Earth through the use of a mathematical principle known as trilateration.  Trilateration is the computation of rectangular coordinates using only distance measurements and trigonometry.  There are two types of trilateration, two-dimensional and three-dimensional.  The old satellite navigational system prior to the creation of GPS, called Transit, used 2-D trilateration while GPS navigation systems use 3-D trilateration.
 In order for 2-D trilateration to work, the locations of three or more reference points are needed as well as the measured distances between the desired point and each reference point.  By knowing at least three reference points and the distances from each point to the desired point, the location of the point can be determined very accurately.  This can be easily understood by the use of circles.  If two distances from a known location were known, a circle around each known location could be drawn using the measured distance as the radius.  Both circles would intersect at two points, meaning there are two possible positions for the desired point.  If there was a third known location, another circle could be drawn using its measured distance away form the desired point as a radius as well.  With three circles, there is only one point of intersection shared by all three making that point the desired location.
 -D trilateration functions under the same principles of 2-D trilateration except that it is working with a three-dimensional axis instead of a two-dimensional plane.  So instead of working with circles, 3-D trilateration works with spheres.  In the GPS navigational system, the system of satellites acts as the known reference points while the receiver acts as the desired point of location.  The purpose of the GPS receiver is to locate at least four or more of these satellites, calculate the distance it is away from each one, and using this data determine its location through the use of trilateration.

← Older revision		Revision as of 21:05, 3 March 2008
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	This site explores the notion of Geocaching using the Delorme Earthmate GPS PN-20 and how various set coordinates may be compared to other coordinates at the same location. Three locations were pinpointed by three group members by recording the coordinates at each location. These locations may be seen in the table below. The other two group members were to find these locations and determine the coordinates at the location. We were then able to compare these coordinates with the set coordinates. By doing this, the accuracy and precision of our GPS system was tested. It turns out that the accuracy and precision was tremendous and only off by a few numbers. Therefore, it may be stated that our GPS system may aid in finding a hidden place a unknown destination. The remaining portion of this site looks at the background of GPS systems,how the GPS navigational system works, GPS uses, personal experience, and other types of GPS systems.		This site explores the notion of Geocaching using the Delorme Earthmate GPS PN-20 and how various set coordinates may be compared to other coordinates at the same location. Three locations were pinpointed by three group members by recording the coordinates at each location. These locations may be seen in the table below. The other two group members were to find these locations and determine the coordinates at the location. We were then able to compare these coordinates with the set coordinates. By doing this, the accuracy and precision of our GPS system was tested. It turns out that the accuracy and precision was tremendous and only off by a few numbers. Therefore, it may be stated that our GPS system may aid in finding a hidden place a unknown destination. The remaining portion of this site looks at the background of GPS systems,how the GPS navigational system works, GPS uses, personal experience, and other types of GPS systems.
−
−	~~==Introduction==~~
−
−	~~This section should include an introduction of the product and a brief description of group members (i.e. who was responsible for which sections or tasks)~~
−

	==History of the GPS system==		==History of the GPS system==

@@ Line 17: / Line 17: @@
 ==How the GPS Navigational System Works==
 GPS, or global positioning system, is a system of satellites, computers, and receivers that can determine the latitude, longitude, and altitude of a receiver located on Earth through the use of a mathematical principle known as trilateration.  Trilateration is the computation of rectangular coordinates using only distance measurements and trigonometry.  There are two types of trilateration, two-dimensional and three-dimensional.  The old satellite navigational system prior to the creation of GPS, called Transit, used 2-D trilateration while GPS navigation systems use 3-D trilateration.
 In order for 2-D trilateration to work, the locations of three or more reference points are needed as well as the measured distances between the desired point and each reference point.  By knowing at least three reference points and the distances from each point to the desired point, the location of the point can be determined very accurately.  This can be easily understood by the use of circles.  If two distances from a known location were known, a circle around each known location could be drawn using the measured distance as the radius.  Both circles would intersect at two points, meaning there are two possible positions for the desired point.  If there was a third known location, another circle could be drawn using its measured distance away form the desired point as a radius as well.  With three circles, there is only one point of intersection shared by all three making that point the desired location.
 -D trilateration functions under the same principles of 2-D trilateration except that it is working with a three-dimensional axis instead of a two-dimensional plane.  So instead of working with circles, 3-D trilateration works with spheres.  In the GPS navigational system, the system of satellites acts as the known reference points while the receiver acts as the desired point of location.  The purpose of the GPS receiver is to locate at least four or more of these satellites, calculate the distance it is away from each one, and using this data determine its location through the use of trilateration.
@@ Line 124: / Line 123: @@
 ****Gives land speed and altitude.
 ****Uses both GPS signals and cellular telephone tower triangulation.
 ****Can search by coordinates in certain models.
 ***Drawbacks:
 ****Phone is insensitive to direction that its pointing, but relies on the vectors of travel.
 ==Personal experiences==
@@ Line 168: / Line 165: @@
 Marc's Personal Experience:
-I found the Earthmate GPS PN-20 pretty interesting.  I got to play with it for at least a day or so, while setting way points for my group-mates to find.  I did not have the manual, so it was a hands-on experience for me from the get go.  From the time I had with using the Earthmate GPS,  it had many tools in aiding a person find their specific location.  The Earthmate GPS had a wide variety of options to view the data and coordinates of the current location, which were divided into a few pages.  One page showed how many satellites that the Earthmate GPS was able to lock onto, and for me it ranged from three to six satellites depending on where I was standing when walking around the university.  Whenever I was surrounded by many buildings or too close to one, the buildings seemed to interfere with the reception of the receiver and the satellites because  the number of satellites it would be connected to would decrease.  When I entered buildings, the receiver lost all connections with any satellites.  Since I was using  this GPS receiver in a city area,  the coordinates were not as accurate as it should be if there were no obstructions causing interference with signals coming from the satellite.  This page not only displayed the number of satellites that the receiver was connected to, but also the coordinates of the current location and a measurement of how off these coordinates were.  At one time, I believed it was plus or minus fifty-six feet, which shows how inaccurate the receiver is when used in areas where the signal can be obstructed.  The coordinates that were calculated would also have huge fluctuations making this receiver even more inaccurate.  It was also very windy that day, which could have also helped in the inaccurate readings.  Another page displayed the path that you were walking, way points in the vicinity, and the speed at which you were traveling.  These were the only two pages that I took interest upon since they were the only two I needed to set way points for my group.  I wish that I have read the manual to some extent because the Earthmate GPS PN-20 is capable of aerial photos as well as USGS topographic maps.  Being able to use these functions of the Earthmate would have probably been a lot more interesting since it is these functions that should have been easy to relate to with the topics of this class, surveying.
+I found the Earthmate GPS PN-20 to be an interesting device to use.  I had it for at least a day or so, while setting way points for my group-mates to find.  I did not have the manual, so it was a hands-on experience for me from the get go.  From the time I had with using the Earthmate GPS,  it had many tools in aiding a person to find their specific location.  The Earthmate GPS had a wide variety of options to view the data and coordinates of the current location, which were divided into a few pages.  One page showed how many satellites that the Earthmate GPS was able to lock onto, and for me it ranged from three to six satellites depending on where I was standing when walking around Drexel University.  Whenever I was surrounded by buildings, the buildings seemed to interfere with the reception of the receiver and the number of satellites connected would decrease.  When I entered buildings, the receiver lost all connections with any satellites.  Since I was using  this GPS receiver in a city area (Philadelphia),  the coordinates were not as accurate as it should have been if there were no obstructions causing interference with signals coming from the satellite.  This page not only displayed the number of satellites that the receiver was connected to, but also the coordinates of the current location and a measurement of how off these coordinates were.  At one time, I believed it was plus or minus fifty-six feet, which shows how inaccurate the receiver is when used in areas where the signal can be obstructed.  The coordinates that were calculated would also contain fluctuations making this receiver even more inaccurate.  It was also windy that day, which could have led to another factor for the inaccurate readings.  Another page displayed the path that you were walking, way points in the vicinity, and the speed at which you were traveling.  These were the only two pages that I took interest upon since they were the only two I needed to set way- points for.  Overall, the manual could have been useful to some extent because the Earthmate GPS PN-20 is capable of aerial photos as well as USGS topographic maps.  Being able to use these functions of the Earthmate would have probably been more intriguing since these functions relate to a class that I am taking called "surveying."
-−
 ==References==
 *"Motorola RAZR V3m Silver Phone (Verizon Wireless)." Amazon.com.3 March 2008 <http://www.amazon.com/Motorola-V3m-Silver-Verizon-Wireless/dp/B000G7LWRM>.
 *"VZ Navigator." Wikipedia. 3March2008. <http://en.wikipedia.org/wiki/Vz_navigator>.

@@ Line 124: / Line 124: @@
 ****Gives land speed and altitude.
 ****Uses both GPS signals and cellular telephone tower triangulation.
 ****Can search by coordinates in certain models.
 ***Drawbacks:
 ****Phone is insensitive to direction that its pointing, but relies on the vectors of travel.
 ==Personal experiences==

@@ Line 17: / Line 17: @@
 ==How the GPS Navigational System Works==
 GPS, or global positioning system, is a system of satellites, computers, and receivers that can determine the latitude, longitude, and altitude of a receiver located on Earth through the use of a mathematical principle known as trilateration.  Trilateration is the computation of rectangular coordinates using only distance measurements and trigonometry.  There are two types of trilateration, two-dimensional and three-dimensional.  The old satellite navigational system prior to the creation of GPS, called Transit, used 2-D trilateration while GPS navigation systems use 3-D trilateration.
 In order for 2-D trilateration to work, the locations of three or more reference points are needed as well as the measured distances between the desired point and each reference point.  By knowing at least three reference points and the distances from each point to the desired point, the location of the point can be determined very accurately.  This can be easily understood by the use of circles.  If two distances from a known location were known, a circle around each known location could be drawn using the measured distance as the radius.  Both circles would intersect at two points, meaning there are two possible positions for the desired point.  If there was a third known location, another circle could be drawn using its measured distance away form the desired point as a radius as well.  With three circles, there is only one point of intersection shared by all three making that point the desired location.
 -D trilateration functions under the same principles of 2-D trilateration except that it is working with a three-dimensional axis instead of a two-dimensional plane.  So instead of working with circles, 3-D trilateration works with spheres.  In the GPS navigational system, the system of satellites acts as the known reference points while the receiver acts as the desired point of location.  The purpose of the GPS receiver is to locate at least four or more of these satellites, calculate the distance it is away from each one, and using this data determine its location through the use of trilateration.

@@ Line 17: / Line 17: @@
 ==How the GPS Navigational System Works==
-GPS, or global positioning system, is a system of satellites, computers, and receivers that can determine the latitude, longitude, and altitude of a receiver located on Earth through the use of a mathematical principle known as trilateration.  Trilateration is the computation of rectangular coordinates using only distance measurements and trigonometry.  There are two types of trilateration, two-dimensional and three-dimensional.  The old satellite navigational system prior to the creation of GPS, called Transit, used 2-D trilateration while GPS navigation systems use 3-D trilateration.
+     GPS, or global positioning system, is a system of satellites, computers, and receivers that can determine the latitude, longitude, and altitude of a receiver located on Earth through the use of a mathematical principle known as trilateration.  Trilateration is the computation of rectangular coordinates using only distance measurements and trigonometry.  There are two types of trilateration, two-dimensional and three-dimensional.  The old satellite navigational system prior to the creation of GPS, called Transit, used 2-D trilateration while GPS navigation systems use 3-D trilateration.
-In order for 2-D trilateration to work, the locations of three or more reference points are needed as well as the measured distances between the desired point and each reference point.  By knowing at least three reference points and the distances from each point to the desired point, the location of the point can be determined very accurately.  This can be easily understood by the use of circles.  If two distances from a known location were known, a circle around each known location could be drawn using the measured distance as the radius.  Both circles would intersect at two points, meaning there are two possible positions for the desired point.  If there was a third known location, another circle could be drawn using its measured distance away form the desired point as a radius as well.  With three circles, there is only one point of intersection shared by all three making that point the desired location.
+     In order for 2-D trilateration to work, the locations of three or more reference points are needed as well as the measured distances between the desired point and each reference point.  By knowing at least three reference points and the distances from each point to the desired point, the location of the point can be determined very accurately.  This can be easily understood by the use of circles.  If two distances from a known location were known, a circle around each known location could be drawn using the measured distance as the radius.  Both circles would intersect at two points, meaning there are two possible positions for the desired point.  If there was a third known location, another circle could be drawn using its measured distance away form the desired point as a radius as well.  With three circles, there is only one point of intersection shared by all three making that point the desired location.
--D trilateration functions under the same principles of 2-D trilateration except that it is working with a three-dimensional axis instead of a two-dimensional plane.  So instead of working with circles, 3-D trilateration works with spheres.  In the GPS navigational system, the system of satellites acts as the known reference points while the receiver acts as the desired point of location.  The purpose of the GPS receiver is to locate at least four or more of these satellites, calculate the distance it is away from each one, and using this data determine its location through the use of trilateration.
+==GPS Uses==
-As long as the GPS receiver is able to lock on to at least three satellites, two possible positions are given.  However, one of those positions is not on the surface of the earth, and therefore can be disregarded.  The more satellites the receiver can lock on to, the higher the accuracy of the calculated coordinates determined by the GPS system.  For example, if the receiver were to lock on to three satellites, three distances would be known and therefore their spheres would be able to drawn, one for each satellite.  However, if there were errors in the data, maybe due to signal interference by obstructions such as buildings, the three spheres would still intersect at one point.  This would cause some error in the determination of the coordinates of the desired point since false data was being used.  However, if a fourth satellite were to be able to connect to the receiver, accuracy would increase and error would be very small because four spheres would not intersect at one point if there were some form of error in the data.  Having four or more satellites, and hence reference points, would help to reduce and estimate error.
+	A GPS can have a wide variety of both military and civilian uses.  GPS can be used in the military to help soldiers find objectives in unfamiliar territory, or to coordinate movements of troops and supplies.  It is also extremely useful in the guidance of ballistic missiles and to point out targets for air strikes and artillery attacks.  One very important feature is that a GPS allows command to pinpoint the location of soldiers caught behind enemy lines, and makes search and rescue missions much easier to complete successfully.  This particular use, search and rescue, can be quite useful to civilians as well.  For example if a hiker is carrying a GPS, rescue teams will be able to pinpoint his location, and bring him to safety much faster than if he was simply lost.  This becomes especially important when the members of the lost party are injured, and are in need of medical assistance.  In an emergency situation, the extra time granted by knowing the location of a person in need of rescue can mean the difference between life and death.
-−
-So how does a GPS receiver calculate its distance from a satellite that it has locked on to?  It does this through the use of radio signals; by calculating the time difference for signals from  a satellite to reach the GPS receiver, the distance away from the satellite can be accurately measured.  Each satellite in the system has an atomic clock, while the receivers have a quartz clock.  The satellite sends a pseudo-random code to the receiver, which it then compares to its internal quartz clock.  The delay in the radio signals is then determined by the receiver, and with this information the distance is calculated.  Quartz clocks are not nearly as accurate as atomic clocks, but since the GPS receiver relies on four or more satellites, the error is negligible.
-−
-==GPS Uses==
-A GPS can have a wide variety of both military and civilian uses. GPS can be used in the military to help soldiers find objectives in unfamiliar territory, or to coordinate movements of troops and supplies. It is also extremely useful in the guidance of ballistic missiles and to point out targets for air strikes and artillery attacks. One very important feature is that a GPS allows command to pinpoint the location of soldiers caught behind enemy lines, and makes search and rescue missions much easier to complete successfully. This particular use, search and rescue, can be quite useful to civilians as well.  For example if a hiker is carrying a GPS, rescue teams will be able to pinpoint his location, and bring him to safety much faster than if he was simply lost. This becomes especially important when the members of the lost party are injured, and are in need of medical assistance.  In an emergency situation, the extra time granted by knowing the location of a person in need of rescue can mean the difference between life and death.
+	GPS also allows for much easier navigation in any vehicle, whether it travels by sea land or air.   GPS navigation systems are becoming more and more common in new vehicles, and are making travel to unfamiliar places much easier for many people across America.  In addition to travel by car, a GPS can also make navigation easier for fishermen, speedboats, even large shipping vessels, as well as any type of aircraft.
 ==Geocaching==
@@ Line 110: / Line 108: @@
 ****Two AA batteries
+[[Image:RAZR.JPG|thumb|right|200px|Common inexpensive RAZR]]
 **Common Cellular Telephone such as the Motorola RAZR V3m
 ***Package includes:
@@ Line 163: / Line 161: @@
 I found the Earthmate GPS PN-20 pretty interesting.  I got to play with it for at least a day or so, while setting way points for my group-mates to find.  I did not have the manual, so it was a hands-on experience for me from the get go.  From the time I had with using the Earthmate GPS,  it had many tools in aiding a person find their specific location.  The Earthmate GPS had a wide variety of options to view the data and coordinates of the current location, which were divided into a few pages.  One page showed how many satellites that the Earthmate GPS was able to lock onto, and for me it ranged from three to six satellites depending on where I was standing when walking around the university.  Whenever I was surrounded by many buildings or too close to one, the buildings seemed to interfere with the reception of the receiver and the satellites because  the number of satellites it would be connected to would decrease.  When I entered buildings, the receiver lost all connections with any satellites.  Since I was using  this GPS receiver in a city area,  the coordinates were not as accurate as it should be if there were no obstructions causing interference with signals coming from the satellite.  This page not only displayed the number of satellites that the receiver was connected to, but also the coordinates of the current location and a measurement of how off these coordinates were.  At one time, I believed it was plus or minus fifty-six feet, which shows how inaccurate the receiver is when used in areas where the signal can be obstructed.  The coordinates that were calculated would also have huge fluctuations making this receiver even more inaccurate.  It was also very windy that day, which could have also helped in the inaccurate readings.  Another page displayed the path that you were walking, way points in the vicinity, and the speed at which you were traveling.  These were the only two pages that I took interest upon since they were the only two I needed to set way points for my group.  I wish that I have read the manual to some extent because the Earthmate GPS PN-20 is capable of aerial photos as well as USGS topographic maps.  Being able to use these functions of the Earthmate would have probably been a lot more interesting since it is these functions that should have been easy to relate to with the topics of this class, surveying.