Global Positioning System (GPS) Workshop · 23/10/2015  · GPS Space Segment •GPS Space Segment...

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: gis-support@elist.tufts.edu

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: gis-support@elist.tufts.edu