Latitude, Longitude, Maps, and Spatial Concepts – Comprehensive Notes
Latitude, Longitude, Maps, and Spatial Concepts – Comprehensive Study Notes
MAP test focus
On the MAP test you may be asked to use latitude and longitude to locate features (continent, mountain range, etc.).
Orientation matters: latitude lines run across (east-west lines), longitude lines run up-and-down (north-south lines).
Normal orientation (north to top) makes latitude parallels run east-west and longitude meridians run north-south.
You should know how to read a latitude/longitude pair and infer the feature or region it points to.
Latitude and longitude basics
Latitude (parallels): lines that run east-west across the map; measured north and south of the equator.
Equator = 0° latitude.
Maximum latitude = ±90° (North Pole = +90°, South Pole = −90°).
Latitudes are parallel and never cross; they circle the globe.
Longitude (meridians): lines that run north-south from pole to pole; measured east or west from the prime meridian.
Prime meridian = 0° longitude, passing through Greenwich, England.
Longitudes go up to ±180° (International Date Line roughly at ±180°).
Meridians meet at the poles and are not parallel on the globe.
Prime meridian, Greenwich, and historical context
The zero longitude line runs through Greenwich, England, with an observatory that helped establish a standard reference for time and longitude.
Historically, many countries used different prime meridians (e.g., New York, Moscow, Beijing), which caused mismatches on maps.
By consensus, Greenwich was adopted as the standard prime meridian, aided by its naval prominence and timekeeping devices.
Degrees, minutes, and seconds (DMS)
Lat/long can be expressed in degrees, minutes, and seconds.
There are 360° in a circle for longitudes; latitude values range from 0° to ±90°.
For the MAP test, you may see degrees, minutes, and seconds, but you should focus on the degrees for calculation purposes.
Practical reading of coordinates
Example: 25°S, 135°E
25° south latitude; 135° east longitude.
Four possible global locations with 12°/104° example (12° latitude, 104° longitude):
12°N, 104°E; 12°S, 104°E; 12°N, 104°W; 12°S, 104°W.
The actual continent/region depends on the sign of latitude (N/S) and longitude (E/W).
Distances/crossings depend on orientation; longitudes converge toward the poles, latitudes do not cross.
Earth shape and geodesy notes
Earth is not a perfect sphere; it is an oblate spheroid (geoid).
Polar circumference ≈ 24{,}860\;\text{miles}; equatorial circumference ≈ 24{,}902\;\text{miles}
The difference between polar and equatorial circumference is about 42\;\text{miles}, which is small but measurable.
Because of rotation, the equator is slightly larger than the polar diameter; the difference matters for precise calculations but not for broad map reading.
Time zones and longitude
360° of longitude / 24 hours = 15° per time zone (roughly).
Time zones are not perfectly aligned with meridians; political boundaries often cut across zones.
Examples: Alabama–Georgia boundary alignment; Florida split time zones; China as a single time zone spanning multiple longitudes.
The International Date Line zig-zags to accommodate political boundaries.
Practical thought questions: If it’s noon in Athens, GA, what time is it in Athens, Greece and in Los Angeles, CA? (Greece is ahead of GA; LA is behind GA.)
GPS and time: GPS relies on satellite time to triangulate positions; civil GPS accuracy typically ranges from roughly tens of feet to around 100 feet, with higher precision in some devices and contexts.
GPS satellites and positioning
About 31 satellites are used to triangulate a position.
Position is given as latitude/longitude (and often as a street address in consumer devices) after conversion.
Satellite coverage allows global positioning, including remote areas like the Gulf of Mexico.
Mount Everest’s position moves due to plate tectonics, roughly about 1–2 inches per year; GPS can monitor such motion.
Maps, projections, and distortions
A two-dimensional map is a projection of the three-dimensional earth; distortions are inevitable.
Projections flatten the globe onto a plane, causing distortions in size, shape, distance, or direction depending on the projection type.
Greenland versus South America size comparison is a classic example of distortion in some projections: Greenland can appear similar in size to South America on certain maps, which is not accurate.
Projections differ in how they handle areas away from the equator; distortions increase with distance from the equator for many common projections.
Historical maps (e.g., Ptolemy) show evolving understanding of the world; later maps improved representation but still relied on projection choices.
Scale, large vs small scale maps
Scale expresses how map distance relates to real-world distance.
A commonly stated example: one inch on the map may correspond to 24,000 inches on the ground for a large-scale map, or to a much larger ground distance for a small-scale map.
Relationship: large-scale maps show a small area in great detail; small-scale maps show a large area with less detail.
The inverse relationship: as scale numeral grows (e.g., 1:24,000 is large scale), the mapped area is smaller; as the scale number grows (e.g., 1:1,000,000 is small scale), the area shown is larger.
Practical demonstration: zooming in on a map (changing scale) reveals more detail; zooming out shows a broader area with less detail.
You may see maps that compare cancer deaths or other phenomena at different scales to illustrate how patterns change with scale.
Density, concentration, and pattern in geography
Density: the number of people or objects per unit area (e.g., people per square kilometer).
Concentration: how those people or objects are distributed across space; two areas may have the same density but different patterns of concentration.
Pattern: the arrangement of a phenomenon in space (clustered, dispersed, linear, circular, etc.).
Examples: population distribution in the U.S. is denser in the East and along the coasts; Canada is concentrated near the U.S. border; deserts have sparse populations (e.g., Australia’s interior).
Why patterns form: factors like proximity to roads or rivers, water availability, climate, economic activity, and land use influence density and concentration.
The why question: when you see a pattern (e.g., high cancer death rates near certain areas), ask why that pattern exists (environmental exposure, socioeconomic factors, access to healthcare, etc.).
Absolute, relative, topological, cultural, socioeconomic, and cognitive spaces
Absolute space: precise coordinates (latitude/longitude) or absolute distance between points.
Relative space: spatial relationships that depend on context (e.g., proximity to cities, cultural or economic ties).
Topological space: connectivity and network flow (e.g., transportation networks, information networks) rather than precise distances.
Socioeconomic space: differences in social and economic conditions across places (income, education, development).
Cultural space: places linked by shared culture, heritage, or immigrant lineage (e.g., Salt Lake City/Provo area as a cultural cluster for certain groups).
Cognitive space: mental images or perceptions of space; mental maps and how people navigate spaces from memory.
Cognitive images and mental maps can influence how people navigate places (e.g., getting lost on campus before a mental map is formed).
Cognitive maps and mental navigation
Mental maps are built from memory, perception, and experience; they influence how people move through space.
Campus navigation example: students may rely on mental maps to determine routes rather than a map alone.
This concept links to how people understand and interpret spatial relationships beyond exact coordinates.
Additional notes on planetary grids and conventions
Other planets and moons can be described with similar grid concepts (equator and prime meridian used as reference lines; the prime meridian origin may be arbitrary on some bodies like Mars or the Moon).
Google Earth and other GIS tools show grids that help you locate places; zoom level changes reveal more lines and data but can introduce distortions if projecting to 2D.
Quick review questions to anticipate on exams
What is the Tropic of Capricorn, and is that a latitude or longitude term? (Latitude; approximately −23.5°)
Which line is the prime meridian, and what is its longitude value? (0° longitude; passes through Greenwich, England)
How many degrees are in a full circle of longitude? (360°)
How many hours are in a day, and how many degrees per time zone? (24 hours; 15° per time zone)
What is the difference between a large-scale map and a small-scale map? (Large-scale = small area, high detail; small-scale = large area, less detail; scale is the ratio like 1:24,000 vs 1:1,000,000)
Why do maps distort reality, and what is a common consequence of projection choices? (Flattening a sphere to a plane causes distortions in size, shape, distance, or direction; Greenland vs South America size exaggeration is a classic example)
How does GPS determine your position, and what is a typical accuracy? (Triangulation from multiple satellites; typical consumer accuracy ranges from ~10–100 feet depending on device and conditions)
What is the difference between absolute and relative space? (Absolute uses precise coordinates; relative uses contextual relationships such as culture, economy, or transportation networks)
Key numerical references to remember
Polar circumference: C_{ ext{polar}} \approx 24{,}860\;\text{miles}
Equatorial circumference: C_{ ext{equator}} \approx 24{,}902\;\text{miles}
Difference: \Delta C \approx 42\;\text{miles}
Full circle of longitude: 360^{\circ}
Time zones: 15^{\circ} per zone
Grid scale example: 1\;\text{in} : 24{,}000\;\text{in ground} (large-scale example)
Satellites: approximately 31 satellites in view for GPS
Concepts tying to real-world relevance
Understanding latitude/longitude helps in identifying continents, mountain ranges, oceans, and other features on maps and on tests.
Time zones influence daily life, travel, and communication across regions.
GIS tools (Google Earth, GPS) rely on the same coordinate framework, but translation to addresses requires additional processing.
Map scale and projection choices affect how we interpret size, distance, and spatial relationships in the real world.
Recognizing density, concentration, and pattern helps explain social, environmental, and health phenomena and informs planning and policy.
Summary takeaways
Latitude parallels run east-west; longitude meridians run north-south.
0° latitude is the equator; 0° longitude is the prime meridian through Greenwich.
Longitudes measure east/west; latitudes measure north/south.
The globe is a geoid, not a perfect sphere; projections cause distortions that vary by region and projection type.
Time zones are based on longitude but are adjusted for political boundaries.
Large-scale maps show small areas in detail; small-scale maps cover large areas with less detail.
Spatial concepts include absolute, relative, cognitive, topological, socioeconomic, and cultural spaces; mental maps influence navigation.