Day 1- Mapping and GPS: Why/What GPS?

Charles Fritz, Ecotrust CanadaNortheast Superior Regional Chief’s Forum

Guardian Watchmen Program, Summer 2015

Global Positioning System (GPS)

• is a space-based navigation system that provides location and time information in all weather conditions, anywhere on or near the earth where there is an unobstructed line of sight to four or more GPS satellites.

• 1957 – sputnik was launched • 1960 – US deployed satellites for government use• 1973 – GPS was coined as the defense navigation

satellite system• 1994 – 5 billion was spent to develop the US

System

GPS Facts

• Consists of 30+ GPS satellites in medium Earth orbit (2000km - 35,000 km).

• Mainly used for navigation, map-making and surveying.

How it works

• 3 Segments to communicate1. Space segment2. Control segment3. User Segment

Diagram of communication

Space Segment

• GPS satellites fly in circular orbits at an altitude of 20,200 km and with a period of 12 hours.

• Powered by solar cells.• The satellites continuously orient themselves to

point their solar panels toward the sun and their antenna toward the earth.

• Orbits are designed so that, at least, six satellites are always within line of sight from any location on the planet.

Control Segments

• The CS consists of 3 entities:

• Master Control System• Monitor Stations• Ground Antennas

User Segment

• This is us! • GPS receiver consists of:

1. an antenna( tuned to the frequencies transmitted by the satellites),

2. receiver-processors, and 3. highly-stable clock( commonly a crystal

oscillator). • They can also include a display for showing location

and speed information to the user.

Finding exact location

• Triangulation:1. By measuring the amount of time taken by radio signal (the GPS

signal) to travel from the satellite to the receiver.

2. Radio waves travel at the speed of light, i.e. about 186,000 miles per second.

3. The distance from the satellite to the receiver can be determined by the formula “distance = speed x time”.

4. Hence receiver’s position find out using trilateration.

GPS Range

Accuracy

• The GPS signal in space will provide a "worst case" accuracy of 7.8 meters at a 95% confidence level.

• Higher accuracy is available today by using GPS in combination with augmentation systems. These enable real-time positioning to within a few centimeters.

What affects accuracy

• The GPS receiver unit (quality);• the position of the satellites at the tie the recording

was made; and• the characteristics of the surrounding landscape.

Accuracy cont

• Ionosphere delay – total electron content in atmospere

• Multipath effects – Bouncing signals off of natural barriers

Augmentation Systems

• Nationwide Differential GPS System• Wide area augmentation system • Continuously operating reference stations

Receiver Types

• Consumer grade • Smartphones <3 m triangulation with cell network• Hiking GPS <3 m correcte, no triangulation

• Survey grade• Trimble survey GPS for industrial activities• <1 cm

Data Collection Using GPS

• GPS data forms one way that spatially referenced data is collected

• Using a coordinate system overlaid on the spherical projected earth

• World Geodetic System 1984• 40° 26′ 46″ N 79° 58′ 56″ W• 40.446° N 79.982° W

GPS data types

• Determined by the proprietary standard1. Waypoints2. Tracks3. Points of Interest4. Routes

Waypoints

• Waypoints are sets of coordinates that identify a point in physical space.

• 40.446° N 79.982° W

• Indicate the single location of a place on the earth, given the current projection and coordinate system

• We will be using waypoints as a means for collecting 90% of our information on the GPS

Routes

• pre-defined paths created from a group of waypoints entered into the GPS receiver in the sequence you desire to navigate them.

• P1:40.446° N 79.982° W• P2:41.446° N 80.982° W• P3:40.446° N 81.982° W

• Will be used as a second method of navigation by preloading them into GPS

Tracks

• Collection of way points that are defined by the GPS receiver.

• Waypoints are automatically collected at an equal interval and then stitched together to form a track or path of your travel

Birch Sites as Tracks

Play around with the GPS!

Day 2- Mapping and GPS: How to GPS?

Outline

• Review of GPS • What we will be doing with the GPS in the field• Hands on exercise

What we know

• GPS is controlled by satellites, control centres, and users

• We create or record data by adding “waypoints” to the GPS

• GPS can also be used for navigating to a point but should not be viewed as the sole form of navigation

What we will do in the field

• Record points in the field at each birch site to verify we arrived to the point

• Use pre-loaded points to aid us in navigating to the birch point

• Record points along roads that may be outdated or mis-classified

What is our GPS?

• Garmin GPS Map 64s• <3 metre accuracy• WAAS and EGNOS enabled

• European Geostationary Navigation Overlay Service

• Quad helix antenna• 16 hours battery life• Withstands incidental exposure to water of up to 1

meter for up to 30 minutes

Device

1. Double Helix Antenna

2. Keys3. Power Button4. Mini-USB port5. MCX connector6. MicroSD slot7. Battery

Compartment

KeysFIND Allows you to search your

recorded points, preloaded points, and points of interest

MARK Select to save your current location as waypoint

QUIT Select to cancel or return to the previous menu or page

ENTER Select to open the options menu for the page that is currently open.

MENU Select to open the options menu for the page that is currently open

PAGE Select to scroll through the main pages

Arrows Use to scroll through menus or the map cursor

IN Select to zoom in on the map

OUT Select to zoom out on the map

Little test #1

1. Turn on GPS 2. Find the compass

HINT: to find this “Page” you will have “scroll” though some “options”

Little test #2

• GPS are capable of telling a time as well, and quite accurately.

• Find out when the sun will rise and set on August 10th, using only the GPS. Oh and how about the moon?

• Sunrise = 6:20• Sunset = 8:57• Crescent (I think)

Bonus

• “Find” an “air transportation” point of interest in for Chapleau

• If you find it, write down the coordinates.

Field Test!!

1. Go outside with GPS, compass, and diameter tape

2. Find a tree3. Collect a waypoint on the GPS4. Record the tree’s latitude and longitude5. Identify the tree species6. Measure the tree diameter at breast height7. Record the bearing of the tree from the office