Review

Powers earned 🐉

• Create (and own) data.
• Start consuming data:
  • CSV, GeoJSON, Shapefile, GeoTIFF, & KML (in this module).
• Practice: visualize bigfoot sightings. Download data.

Tip 💯

• Most desktop apps use a right-click for various functions.
• Get a mouse for your laptop
• or discover the magic gesture.

Extra Pro Tip 💯

• Understand what needs to be submitted for evaluation.
• Don't know what to submit?
• Ask us. Before the assignment is due.

Where are people?

• In cars? 🔗
• In trains? 🔗
• In boats? 🔗
• In airplanes? 🔗

Reference maps

• A detailed record of natural and human-made features.
• Navigation is primary purpose.
• U.S. Geological Survey (USGS) topographic maps. 🏅✨
  • History and map symbols

Reading USGS maps

• Use this USGS topographic map viewer
• Find your neighborhood.
• Find a map that was published before you were born.
• Find a map that was published before your parents were born.

Reading USGS maps

• Explore Lexington West topographic maps from 1906–2022 via this QGIS project
• Find the scale, north arrow, and lat, lon values on the map.

Slippy vs static maps

• Slippy, aka dynamic, maps change as you pan and zoom.
• Static maps do not change – they are meant to be printed at a fixed size.

We'll make static maps

• Implications?
• We need to aware of the map's scale and orientation, both of which are tied to its projection.

Map scale

• How much is the map reduced from the real world?
• Commonly expressed on the map as scale bar and representative fraction.

Scale bar

• Graphic scale using a printed measuring rule on the map.
• Maintains accuracy when map is enlarged or reduced.

Representative fraction

• Ratio of map distance to ground distance.
• 1:10,000 (1/10,000) means 1 unit on the map equals 10,000 units on the ground.
• Not accurate when map is enlarged or reduced.

Verbal scale

• 1 in to 2,000 feet
• Not accurate when map is enlarged or reduced.

Map orientation

• Which way is north?
• Allows you to use a compass for navigation.

Compass bearings

• Desired direction of travel is called a bearing.
• Relative to north in degrees (0–360).

Virtual geocache

• X number of locations that you need to find
• using distance and bearing.
• Visit this page to start.

Nearest geocache

• From our lecture room is 448 feet at 169°.
• Walk in that direction. "View" is the clue.
• When close, another clue will help you identify the feature.
• ☠️ Watch out for hazards ☠️

Tips

• Cache clearly identifiable – if you follow clues.
• Work in teams.
• Walk slowly when close. Look around, up, down, etc.
• Use compass app to help with bearing.

Walk for 20 minutes

• at exactly 3 miles per hour.
• Where would you be?
• Dead reckoning.

Earth

• moves 15° of longitude per hour.
• Time zones roughly follow these divisions.

A good clock

• can tell you where you are.
• Compare local time with home port time.

Your clock says 10 am

• The sun is rising.
• On this day at the home port, the sun rose at 6 am.
• Four hours difference = 60° west of home port.

1759

• John Harrison's H4 chronometer.
• Allowed accurate time at sea, thus accurate longitude.
• Two short videos follow.

1970s

• We make atomic clocks
• that keep the best time measurements (like ever).

1995

• These clocks are put in satellites
• that broadcast their time and location to us
• with global coverage.

Global positioning system (GPS)

• US satellite-based navigation system.
• Constellation of (at least 24) satellites.
• One of many global navigation satellite systems (GNSS).

How?

• Satellites broadcast their location and time.
• Signals travel 186,000 miles per second.
• Difference in time between satellite and receiver is used to calculate distance.

🤯

• Miles to satellite =
• time difference * 186,000 miles per second.
• Four satellites needed to calculate 3D position.

Accurate?

• You tell me.
• Was much less accurate before 2000.

2000s

• iPhone and Street View
  • use GPS to geocode other data.
• Enable Street View for this map.
• In 2019 10+ million miles mapped with GPS.
• And, now there's Dog View...

Privacy?

• Your location is a commodity
• Do you mind if private companies log your location?
• Do you mind if they sell it to other people?
• Check your apps...

IKnowWhereYourCatLives.com

• and where you do, too.
• Experiment to show how much location is shared on social media
• often without the poster's knowledge.

Our collaboration

• We made CSVs of 650+ places
• that are meaningful to us.
• View the interactive map.

Responsibilities

• 1. Data must be formatted properly.
• 2. Points must accurately represent locations.
• Otherwise can't build map and it won't be meaningful.

Analysis

• Where are the most popular places?
• Dense cluster of points
• show places that are meaningful to many people.

Heat map

• Shows clusters as 'hot spots'
• and identifies general patterns.

Voronoi polygons

• Create polygon layer from points
• where each polygon shows area closest to generating point.

Largest polygon

• Most 'exotic' location.
• "Small cave opening at natural spring"

Smallest polygon

• Most 'chosen' location.
• Wildcat statue

Download your data

• CSV 🔗
• GeoJSON 🔗
• Voronoi Polygons 🔗

To make the world flat

• we project the sphere's latitude & longitude onto a plane.
• Besides a globe, every map uses a projection.

Why?

• Try using a globe to find your way around.
• Measure distance and area more easily.

Coordinate systems

• The globe is divided into an interval of lines
• on which we make measurements.
• Unit of measure
  • angular: degree
  • linear: meter or foot

Shape of earth

• Define sphere-like shape of earth
• and measure with latitude and longitude.
• Graticule
• with angular unit of measure.

WGS 84

• Coordinate system used by GPS.
• 38.05°, -84.50°
• Reference code is EPSG:4326

Earth flattened

• Project sphere-like shape onto flat surface
• using a cylinder, cone, or plane.
• Makes a grid
• with linear unit of measure.

🔍 Gotchas

• Distortion.
• When you project a sphere onto a plane you can maintain:
  • area (equal-area projections)
  • shape (conformal projections)
• But not both on the same map.

🔍 Handle gotchas

• Primary goal: minimize distortion.
• See how circles distort on different projections. 🔗
• Find a suitable projection for map's scale and intent. 🔗
• Take GEO309 to learn more!

Practical advice

• Let's focus on five projections.
  • Equirectangular
  • Mercator
  • Equal Earth
  • Albers equal-area
  • Local conformal

EPSG codes

• European Petroleum Survey Group
• makes 4–6 digit codes for coordinate systems.
• Why are they concerned about map projections?
• They have become the de facto standard – use their codes!

Equirectangular

• EPSG: 4326
• Lines of latitude and longitude make squares.
• Default projection for data in WGS 84, i.e., GPS coordinates.
• Distorts area and shape – don't use it!

Mercator

• EPSG: 3857
• Lines of latitude and longitude are parallel.
• Default projection for most web maps.
• Preserves shape but distorts area.

Equal Earth

• EPSG: 8857
• Good projection for world maps.
• Preserves area but distorts shape.

Albers equal-area

• EPSG: 102008
• Good projection for North America.
• Preserves area but distorts shape.

Local conformal

• EPSG: 3089 (for Kentucky)
• Tuned to small areas like states.
• Minimizes distortion of shape and area.

Different state?

• Search epsg.io
• and ask us!

Why worry about projections?

• It's complicated, but
• when you pick the right one you can measure stuff
• and cats sleep better.

Requirements

• Documentation
• No screen capture video
• Let's do it live in class!

Reference maps

• What is their primary purpose?
• What two elements of a reference map do we look for?
• What is a bearing?

GPS

• What is required for GPS to work?
• What are the privacy concerns using GPS?
• What coordinate system does GPS use?

Projections

• What is the goal of a map projection?
• Name two types of distortion produced by a projection.
• What five projections do we use?