Global Positioning System (GPS) Workshop Written by Barbara Parmenter
Updated by Carolyn Talmadge
Tufts Geospatial Services
GIS at Tufts http://gis.tufts.edu
E-mail: [email protected]
Geospatial Tools at Tufts
• Geographic Information Systems (GIS)
• Remote Sensing
• Global Positioning Systems (GPS)
• GPS Activity
Geographical Information Systems (GIS)
A system of computer software, hardware, data and personnel to help create, visualize, store, manipulate and analyze information that is tied to a spatial location.
• GIS shows the world as a stack of layers
• Each layer represents a particular class of features or phenomena
Buildings
Roads
Water
Elevation
Schools, Hospitals
Aerial/Satellite Imagery
How does GIS work?
• Data comes in different formats and from different sources • Points
• Lines
• Polygons
• Rasters (pixels)
• Layers are stacked on top of each other and can be turned on or off
• Data can be mapped and analyzed in relation to each other
Towns Towns + Hydrology Towns + Hydrology + Open Space Towns + Hydrology + Open Space + Flood Zones Towns + Hydrology + Open Space + Flood Zones + Fire St. Towns + Hydrology + Open Space + Flood Zones + Fire St. + Roads
Benefits of Spatial Representation
Are there relationships between income and tree cover?
Medium Income & Canopy Cover
GIS allow users to:
• Visualize and interpret patterns and relationships
• Analyze spatial information and trends
• Ask interactive spatial questions
• Predict future impact and create models
• Develop effective solutions
• Display and communicate spatial information
Remote Sensing
Remote Sensing • Imagery produced by monitoring devices that don’t
make physical contact
• Aircraft, spacecraft, or satellite.
• Measure variations in the way earth surface features reflect and emit electromagnetic energy.
Human eyes see a small portion of the EM spectrum = The Visible Spectrum (ROYGBIV)
Sensors detect variations in energy in both the visible and non-visible areas of the spectrum
• Surface features reflect or absorb the sun’s radiation in different ways.
• Identify earth surface features by their spectral reflectance patterns.
Information Extracted by Remote Sensing
Types Example
Classification Land Cover, Vegetation, Populated Areas
Change Detection Land cover change over time, Before/ After - Natural Disaster, Shoreline Change
Extraction of Physical Quality Temperature, Precipitation, Elevation
Identification of Specific Features Forest Fires, Floods, Archaeologic Features, Earthquakes, Extreme Weather Events
Aceh City pre and post tsunami
Vegetation Index of the World, Map by NASA/NOAA
“Lights at Night” dataset used as a proxy for economic growth
Earthquakes since 1898, by Magnitude
Global Positioning Systems (GPS)
A system of satellites & receiving devices used to compute positions on the Earth. 1. Space Segment 2. Control Segment 3. User Segment
GPS Space Segment
• GPS Space Segment consists of a constellation of satellites transmitting radio signals to hand held GPS devices.
• Fly in “Medium Earth Orbit”
• U.S. Air Force maintains at least 24 GPS satellites, but currently flies 31.
• Satellites are divided into 6 equally spaced orbital planes, with 4 satellites on each plane.
• Each satellite circles the Earth 2x/day
• Requires 4 satellites for accurate location reading
Control Segment
• A global network of ground facilities that: • Track the GPS satellites • Monitor their transmissions • Perform analyses • Send commands and data to the constellation.
GPS units calculate the time and distance to at least 4 satellites in order to locate your position on the earth (Latitude & Longitude).
Latitude & Longitude
• Latitude = Expresses how far North or South you are from the equator. Expressed as Degrees North (+) or Degrees South (-) • Horizontal parallels that run east/west . • They run from 0° (equator) to 90° (at the North/South Poles).
• Longitude = Expresses how far East or West you are from the Prime
Meridian. Expressed as Degrees East (+) or Degrees West (-) • Vertical meridians that run North/South • They run from 0° (Prime Meridian) to 180° East/West
Geographic Coordinates
• Intersection of Latitude/Longitude = Your position on Earth (XY)
• Longitude represents the X Position
• Latitude represents the Y Position
• Units = Degrees, Minutes, Seconds or Decimal Degrees • Can convert Between the two
X
Y
Boston Lat (Y) = 42.3601° Long (X) = -71.0589°
GPS User Segment
• Accuracy • Handheld: 1-10m • Differential GPS: 3m – 1cm
• Cost
• Handheld: $150 - $400 • DGPS: $2,500 and up • Juno ST (DGPS) sub 2-3m, $600
• Preparation
• Tree canopy, urban canyons, tall buildings, etc.
• Ruggedized Unit
• Bring extra batteries, car charger, etc.
• Capture additional data while doing survey
GPS Data
• Records locations of features (visible/non-visible) in the field: • Pollution/emissions monitoring
• Water testing data
• Wells
• IDPs/refugees
• Dwellings
• Survey Locations
• Animal tracking
• Storm surge run up
• Hiking Trails
• Pot Holes
GPS Field Work
• You need GPS when:
• You can’t see the features in available imagery
• You need to record other information (attribute information) about the features
• Measured data
• Survey information
• You may not need GPS if you can see features on aerial photography (e.g., in Google Maps)
GPS Data
GPS surveys provide location data (latitude & Longitude) to input into GIS
GPS Field Work: IDP Community Surveys
Internally Displaced Persons: Santa Marta, Colombia
Location of IDPs
Dr. Karen Jacobsen Feinstein International Center
Information Collected: • Location • City of origin • Age • Sex • Race • Time in new location • Reason for fleeing • # IDPs at location • Work /income • Destination?
Map of Centro barrio in Santa Marta depicting random sample points
GPS Field Work: Health Tracking
Monkey Locations in Kathmandu
Field Data Collection Preparation
• Determine all the additional information (attributes) you need to collect.
• Prepare a collection sheet
• Example: Elephant Dung Sampling project in Nepal
Field Data Collection Preparation
Think like a Database!
GPS ID Waypoint
ID Date Time Lat (Y) Long (X) Habitat Landscape
Vegetation Density Sample
1
Vegetation Density
Sample 2
Vegetation Density Sample
3
Elephant Number
Dung
Elephant Dung Age
Sheep Number
Dung
Sheep Dung Age
Cattle Number
Dung
Cattle Dung Age
Sample 1: Eggs Present
(Y/N)
Sample 2: Eggs Present (Y/N)
15 1 10/1/2015 1:12pm 42.24161165 -71.5416517 Dry Forest 0.25 0.75 0.77 2 Fresh 0 NA 15 Old Y Y
15 2 10/1/2015 3:10PM 42.65165189 -71.1451652 Running Water Meadow 0.75 0.38 0.54 0 NA 0 NA 0 NA N N
15 3 10/1/2015 3:25PM 42.62615412 -71.1591652 Muddy Forest 0.38 0.21 0.25 3 Old 1 Frest 0 NA N N
15 4 10/5/2015 10:16Am 42.58161652 -71.1516165 Dry Wetland 0.21 0.54 0.51 0 NA 0 NA 10 New Y N
15 5 10/5/2015 11:20Am 42.32291152 -71.0120321 standing Water
- puddle Wetland 0.54 0.51 0.645 0 NA 3 old 1 New Y Y
15 6 10/5/2015 1:45PM 42.82118156 -71.3215151 Running Water Other 0.51 0.31 0.51 1 Recent 0 NA 0 NA Y N
15 7 10/7/2015 10:00Am 42.32518515 -71.5145151 Muddy Forest 0.31 0.15 0.99 0 NA 1 Recent 0 NA N N
15 8 10/7/2015 11:05Am 42.52651166 -71.3215116 Dry Wetland 0.15 0.841 0.5 0 NA 3 Recent 0 NA N N
15 9 10/7/2015 1:35PM 42.12151838 -71.3218592 Muddy Other 0.841 0.94 0.12 5 Old 0 NA 5 Recent N N
15 10 10/7/2015 2:05PM 42.35685183 -71.2165913 standing Water
- puddle Meadow 0.94 0.22 0.54 1 Recent 0 NA 12 Old N Y
Let’s collect data outside…
Let’s collect data outside…
Why write down the GPS Unit Number and the Waypoint Number? Why write down the
coordinates?
Major points….
• Plan ahead and be prepared
• Prepare a data collection sheet. Think like a database!
• Plan for backing up your work (Chaos, theft, loss, etc.)
• Practice before you leave for the field
Other GPS resources at Tufts…
Let’s head out We’ll talk and learn about the GPS units outside
Then split into groups of two and collect waypoints
Follow the PowerPoint from here on… We’ll walk around and help you
Major Tip: Split the screen so that the PowerPoint takes up just half or less, and you can see the other programs and follow along…
Create a folder in your home (P or H) drive (or other drive) to save your files.
Downloading data from the GPS unit
1. Turn on your GPS unit
2. Plug your GPS unit into the USB port using the USB cord
3. Wait until you get message that Garmin USB GPS driver successfully installed
Downloading Software for the GPS Data
• We use a freeware program called DNRGPS
• From Minnesota Department of Natural Resources
• You don’t need to download this in the lab We have it installed already – next slide!
Open DNRGPS
• In the Data Lab, go to Start – All Programs – GIS Applications – DNRGPS
• In Mugar lab, go to Start – All Programs – GIS – DNRGPS
• Or search for the program in the start menu
After opening DNR GPS, you should see it connecting to your unit…
We will download both Waypoints and Tracks
To download your waypoints…
If this box pops up, select the Waypoints with the collection date!
You should see something like this…
First, save as a Google Earth KML file… Save the KML file in your new GPS Tutorial Folder in your P Drive (or selected drive). Name the file: Waypoints_Google.Kml and change the Save as Type to .kml
To download your Tracks…
IF this box pops up, select Current.GPX!
- Click on the Tracks Tab - Then go to Track > Download
You should see something like this…
Again, save as a Google Earth KML file… Save the KML file in your new GPS Tutorial Folder in your P Drive (or selected drive). Name the file: Tracks_Google.Kml and save as a .kml
When this box appears, select Line
Open your GPS Tutorial Windows folder and double-click on your Tracks_Google.KML file …
Immediate Gratification
Now, lets pull in the waypoints! 1. In Google Earth, go to File > Open
2. Navigate to your GPS Tutorial Folder, and select Waypoints_google.kml. Press Open.
Now we can quickly and easily see our tracks & our waypoints in Google Earth.
• Are your tracks and waypoints accurate? • Use the Pan Hand to move around the map. Use the mouse roller to zoom in and out. • Click on the points to get more information collected by our GPS Unit
That was easy! Now, lets save our DNRGPS waypoints in a different format so we include the information we collected on our field data collection sheets!
Go back to DNRGPS and click on the Waypoints tab
Save to a tab-delimited text file…
Make sure it is Text File (Tab-
delimited) (*.txt)
Name the file Tufts_Waypoints
This is what a tab-delimited file looks like if you double-clicked it…
It’s a common format for database files…
But we need to create an Excel file in order to include the info you collected in your field data collection sheet 1. Open Excel
2. Choose File > Open. Find the tufts_waypoints.txt file you just saved
Change this to All Files
Press Finish
Delete unnecessary columns…
You can decide – just make sure to keep the IDENT (waypoint ID) column and your Latitude and longitude columns. Maybe time as well!
Save as an Excel (.xlsx) file…
Add the information from the field collection sheet and save again…
Add a column for • GPSUnit • Feature_Type • Name_Feature • Purpose • Remarks • Don’t worry about Materials &
Conditions
Fill in the information from your data collection sheet.
For backup purposes (your computer is stolen, the GPS unit drops in the river)…
• Print out copies
• Save your field collection sheets!!
• E-mail or upload the Excel file somewhere safe
• (However, you don’t have to do these things today during our workshop)
• For now, close Excel
Tip: every Tufts student and faculty has access to 50gb of cloud storage through tufts.box.com
Now that the excel file is filled out with our field collection information AND the GPS location information, we will learn how to open our point data in Google Maps!
If you have a Gmail or Google account, go to maps.google.com and sign in.…
Click on the Menu Then select “My maps” .
1. Press Create Map to open a new map.
2. Press Import to open your Excel File
Now we’ll select the columns that will determine the location of the points.
Check Latitude and Longitude Then press Continue
Now we’ll select the column that will determine the Name of the points – Ident will suffice.
Check Ident Then press Finish
Now, all our points are in Google Maps!
If you click on a point, it now has the GPS information AND the information we collected!
Click on Tufts_Waypoints.xlsx. Let’s change the name to Points of Interest. Then click on Uniform Style. Change the “Group Places by” to Purpose. Then press x. Now all your points categorized by their purpose! This is called symbology. Try changing this to your other fields that you collected.
Let’s bring in our Track data too! We can import that original Track_Google.KML layer directly into google maps!
1. Click Add Layer and then click Import
2. Click Select a file from your computer and then navigate to Tracks_Google.kml. Press Open.
Now we see our tracks and our Points! 1. Let’s change the name of the map from Untitled Map to Tufts University to make it complete.
Last step. Now we can save this map and reopen it in Google Earth with all the survey information!
1. Press the 3 dots next to share
2. Select Export to KML 3. Press Download
Open the downloaded file Now you should be able to see your points + the information you added from your excel sheet alongside your original KML points.
There are several ways to import your data into ESRI ArcMap (Optional)…
1. From Google Earth: • Save your Google Earth Waypoints as a .KMZ and open in GIS
• Here is a link to the Tufts tutorial on how to Open Google Earth Files in GIS
2. From DNRGPS: • Save directly as an ESRI shapefile from DNRGPS
• Save as a .TXT file and Import using “Add XY Data”
• Refer to Downloading GPS Data with DNRGPS & Importing into ArcMap
Questions? This PowerPoint can be found on the Tufts GIS Center web site – http://gis.tufts.edu – under Online Tips and Tutorials – GPS Guides
Good luck & Happy Mapping
Carolyn Talmadge
GIS Specialist, TTS
GIS at Tufts http://gis.tufts.edu
E-mail: [email protected]