Introduction to Geographic Technologies Global Positioning System (GPS) Global Information System (GIS)

Introduction to GPS

What is GPS Global Positioning System Satellite system: measure time velocity gives the user a precise location. 24 satellites that circle the Earth constantly providing information to users. Developed an maintained by the Department of Defense (DOD) in 1972.

GPS Components Space Segment = Satellite User Segment Control Segment = User Segment Monitoring stations Satellites are the space component of this system: There are 24 of them that orbit over 12,000 miles above the surface of the earth sending/receiving signals from the ground. Monitoring stations are the surface components: These are stations around the globe that send/receive signals from the satellites. User equipment: the equipment that the user is using isn't has important as the idea that the satellites send the final location to the user through a system called triangulation. User equipment DOES NOT send information back to the satellites. Any GPS enabled device does the same process.

Think-Pair-Share Think: Recall a time that you have used GPS and it has been wrong. What happened? How did you fix it? 2 minutes Pair: Turn to your elbow partner 20 seconds Share: your experience with your partner(s). Share out with class Timing for T-P-S: Think: Allow students to process and write down their thoughts on paper. This will help students focus what they want to share to their partner. Time needed will vary with the class and their needs, if you see that students are still writing after the 2 minutes, adjust the time. If you see the majority of the class is done early, quite time early. Taking time on your phone or iPad allows for the time adjustment and an end time alert. If you do not have a device that can perform this function, here is a link to an online stopwatch: http://www.online-stopwatch.com/classroom-timers/ Pair: give students about 20 seconds to find their elbow partner. This is usually the person next to them. There are some variations when students are absent, groups of three may develop, just monitor the room to ensure there are meaningful conversations during share time. If this technique is used often in class, it is helpful to have pre-assigned partners to keep this time to a minimum. Share: Give the students a predetermined time so that conversations are focused on the topic. Start the class off with 2-3 minutes. Monitor the classroom to make sure that there are meaningful conversations. Extensions: It may be worth the time to have a quick recap of the share session as a class. Students can raise their hand and share what they had to say with the class. Instructor can also pick students that may need redirections to hold them accountable for their contribution to the activity. This will add credibility to the time spent in this session and students will get more out of the time.

Component Interaction

Space Segment A constellation of 24 orbiting satellites Orbit at a distance of 11,000 miles above Earth (middle atmosphere) Each satellite contains several very precise atomic clocks orbit roughly every 12 hours 24 Orbiting Satellites 3-4 spares

Control Segment: Time is of the Essence There are five Control Stations around the world Stations monitor satellites as they pass overhead by measuring the distance from the control station to the satellites Master control station determines satellite conditions (orbit, clock, health status) and calibrates the satellite’s clock

Map of Monitoring Stations

User Segment Accuracy is dependent on the kind of receiver Navigation (Recreation) grade – least accurate Mapping grade – accurate Survey grade – most accurate Costs range from $100 to $30,000 Note the accuracy of the different user segments. Point out to studetns that the GPS on their phones is not as accurate as the industry grade equipment.

Think-Pair-Share You use the GPS on your phone for directions and maps all the time. You will have 3 minutes to free write the following in journal: Think: Why do you think the GPS for “recreational use” is the least accurate? HINT: think of who developed the GPS technology. 3 minutes Pair: turn to your elbow partner 20 seconds Share: your experience with your partner(s). 2 minutes Share out with class Timing for T-P-S: Think: Allow students to process and write down their thoughts on paper. This will help students focus what they want to share to their partner. Time needed will vary with the class and their needs, if you see that students are still writing after the 3 minutes, adjust the time. This activity warrants more time because the students have to look back in their notes or recall the information, not an experience. This may take more time. If you see the majority of the class is done early, quite time early. Taking time on your phone or iPad allows for the time adjustment and an end time alert. If you do not have a device that can perform this function, here is a link to an online stopwatch: http://www.online-stopwatch.com/classroom-timers/ Pair: give students about 20 seconds to find their elbow partner. This is usually the person next to them. There are some variations when students are absent, groups of three may develop, just monitor the room to ensure there are meaningful conversations during share time. If this technique is used often in class, it is helpful to have pre-assigned partners to keep this time to a minimum. Share: Give the students a predetermined time so that conversations are focused on the topic. Start the class off with 2-3 minutes. Monitor the classroom to make sure that there are meaningful conversations. Extensions: It may be worth the time to have a quick recap of the share session as a class. Students can raise their hand and share what they had to say with the class. Instructor can also pick students that may need redirections to hold them accountable for their contribution to the activity. This will add credibility to the time spent in this session and students will get more out of the time.

How GPS Works Takes the data from the satellites: Distance = Travel Time x Speed of light The signal from the satellite is traveling at the speed of light It is ideal to use the data from 4 satellites 3 satellites will work Factor in the distance from the Earth’s surface.

How is GPS position determined? TRIANGULATION . Suppose the distance from Satellite A to our position is 11,000 miles At this point we could be located anywhere on the specified sphere Satellite A + Next, let us take another measurement from a second satellite, Satellite B Satellite B Now our position is narrowed down to the intersection of theses two sphere

How is GPS position determined? TRILATERATION . Satellite C + Satellite A Satellite B Taking another measurement from a 3rd satellite narrows our position down even further, to the two points So by ranging from 3 satellites we can narrow our position to just two points in space These points are located where the 3rd sphere cuts through the the intersection of first two spheres

How is GPS position determined? TRILATERATION . Satellite C + Satellite A Satellite B We could make a 4th measurement from another satellite to determine the true point However, GPS receivers use a 4th satellite to precisely locate our position We can eliminate one of the two points that gives a ridiculous answer The ridiculous point may be too far from the earth OR

Satellite Trilateration Using 4 satellites provides the user with an accurate location

GPS Accuracy GPS is accurate, however there can be sources of error. Dilution: the arrangement of satellites is not ideal MultiPath: obstacles that will bounce the satellite signals. Signal noise: one or more satellite has dipped out of range.

Geographic Information Systems Introduction to GIS Geographic Information Systems

Geographic Information Systems GIS is a spatial database with a strong visual display component GIS is not just a mapping program GIS was developed in the early 1980s It’s expansion beyond the environmental sciences been slowed until recently Currently it is used in many diverse industries including health care, political science and law enforcement. Insert a map of your country.

What can you do with GIS? Maps come to life! Literally ALL maps can come to life with the right set of data: Land Elevation Population density Distance to places of interest (parks, grocery stores, schools, etc.) Environmental factors: Noise, light, etc. Anything that can be associated with a location. Insert a map of your country.

How is this Possible? Each GIS map has layers that are made up of objects that are alike. The layers are build upon the real map of the area. Insert a map of your country.

Layers contain features Insert a map of your country. Theses features are arranged in polygons of area representing data.

Layers contain features Insert a map of your country. Theses features are arranged in color coded dots representing data on projected economic growth.

Geographic Information systems Insert a map of your country. Theses features are arranged lines tell the story of public transit in an area.

Raster Data Model The first GIS model developed Based on grids of cells Each cell are assigned number values Values and cells grouped into layers Used for surfaces that have NUMBERIC value Ex: elevation, temperature, precipitation Insert a map of your country. Each square represents an elevation. When put together a picture is formed.

Think-Pair-Share The most common type of raster model is the digital photograph. What data numbers are registered for the “grid”? Have you ever seen a representation of the raster model in a digital photograph? Explain. 3 minutes Pair: Find your elbow partner Share: What is your theory? Explain your thoughts to your elbow partner. 2 minutes Collaborate Timing for T-P-S: Think: Allow students to process and write down their thoughts on paper. This will help students focus what they want to share to their partner. Time needed will vary with the class and their needs, if you see that students are still writing after the 2 minutes, adjust the time. If you see the majority of the class is done early, quite time early. Taking time on your phone or iPad allows for the time adjustment and an end time alert. If you do not have a device that can perform this function, here is a link to an online stopwatch: http://www.online-stopwatch.com/classroom-timers/ Pair: give students about 20 seconds to find their elbow partner. This is usually the person next to them. There are some variations when students are absent, groups of three may develop, just monitor the room to ensure there are meaningful conversations during share time. If this technique is used often in class, it is helpful to have pre-assigned partners to keep this time to a minimum. Share: Give the students a predetermined time so that conversations are focused on the topic. Start the class off with 2-3 minutes. Monitor the classroom to make sure that there are meaningful conversations. Extensions: It may be worth the time to have a quick recap of the share session as a class. Students can raise their hand and share what they had to say with the class. Instructor can also pick students that may need redirections to hold them accountable for their contribution to the activity. This will add credibility to the time spent in this session and students will get more out of the time.

Example Each square is a reflection of light (number). Broken down by pixels, making each pixel smaller and smaller creates a clearer picture.

Vector Data Model Vector Model House Road Archaeological Site Uses points, lines, and polygons define data classes Grouped into themes or layers House Archaeological Site Road

R H R R R S S S R S S S S R S S S R S S

Each line (vector) is connected . House Road Archaeological Site

GIS Models - Combined Using a combination of raster data imagery and vector layer files to build our geo-database Let’s see a real-world application

Exit Ticket On your scratch sheet of paper fill in the answers to the following: GIS is an acronym for _________________. Two uses for GIS are ___________________. The two major data arrangements of GIS are_____________ and _______________.