1 - The Nature of Physical Geography#
1.1 - What Is Physical Geography?#
Physical geography is the study of spatial distributions of phenomena across the landscape, processes that form and change those distributions, and implications for those distributions on people, animals, and plants. Geography is both a natural and a social science.
1.2 - How Do We Investigate Geographic Questions?#
Geography utilizes approaches from the natural and social sciences, blending them together in a geographic approach.
The conceptual basis of the questions geographers pose lies in the notion that the location of something affects, and is a product of, other features or processes in both the natural and human environment, and of interactions between them.
1.3 - How Do Natural Systems Operate#
Earth consists of 4 overlapping spheres: the atmosphere, biosphere, hydrosphere, and lithosphere.
Open systems allow matter and energy to move into and out of the system.
Closed systems do not exchange matter, or perhaps even energy, with its surroundings.
1.4 - What Are Some Important Earth Cycles?#
Atmospheric cycles move matter and energy in the atmosphere, causing wind and other aspects of weather.
The hydrologic cycle, or the water cycle, involves the circulation of water and associated energy in the hydrosphere.
The rock cycle describes the movement of matter and energy on and below the Earth’s surface, including processes like erosion, uplift, burial, and melting.
1.5 - How Do Earth’s Four Spheres Interact?#
Atmosphere-Hydrosphere: Evaporation, clouds, precipitation
Atmosphere-Lithosphere: Volcanoes, weathering
Atmosphere-Biosphere: O\(_2\)-CO\(_2\)
1.6 - How Do We Depict Earth’s Surface#
A shaded-relief map emphasizes the shape of the land by simulating light and dark shading on the hills and valleys.
1.7 - What Do Latitude and Longitude Indicate?#
If a plane intersects with the center of the Earth, it is called a great circle. It indicates the shortest distance between two points.
A small circle intersects a sphere without touching the center.
1.8 - What Are Some Other Coordinate Systems?#
Universal Transverse Mercator (UTM)#
The Universal Transverse Mercator (UTM) system is a method of identifying locations across the nonpolar part of Earth.
The UTM system slices the nonpolar region into 60 north-south zones, each \(6\degree\) of longitude wide. The slices are numbered from 1 to 60, with numbers increasing wastward from the International Date Line.
The slices are further subdivided into grid zones, each \(20\degree\) of latitude long. The purpose of UTM is to ensure that the location is accurate at the center of these zones, with increasing distortion toward the edges.
For a location within a grid zone, we specify coordinates as northings, a measure of the position north or south of the equator, and eastings, a measure of the number of meters east or west of the central meridian for that zone.
The advantage of UTM is that it is measured in meters.
Converting distances between UTM zones can be more difficult, however.
State Plane Coordinate System (SPCS)#
The State Plane Coordinate System (SPCS) is a third system of mapping, used only in the US. The SPCS system uses X-Y coordinates to represent locations on flat planes, simplifying land surveys and calculations of distances. Under the SPCS, states are divided into state plane zones.
Public Land Survey System (PLSS)#
The Public Land Survey System (PLSS), or the Township-Range Survey System, is used in the US for specifying the location of lands and for subdividing larger land parcels into smaller ones.
The PLSS was designed later than the SPCS, taking advantage of improved surveying technologies and protocols.
The PLSS is based around some initial point. A Principal Meridian extends north and south and a Base Line extends east and west. Beginning from the Principal Meridian, the land is subdivided into six-mile-wide north-south strips called ranges. Beginning at the Base Line, the land is subdivided into six-mile-wide east-west strips called townships.
Each township-range grid square is subdivided into 1-mile wide sections.
Each one-mile section can be further divided into quarters, eighths, or smaller subdivisions.
1.9 - How Do Map Projections Influence the Portrayal of Spatial Data?#
Conformal projections are map projections that attempt to preserve shapes.
Equal-area projections are map projections that preserve areas but distort shapes.
Sinusoidal projections are maps that are created by “unpeeling” the sphere of the Earth and flattening the pieces.
Straight, parallel lines remain parallel and have their correct lengths.
Areas are preserved, but shapes are distorted near the edges.
In cylindrical projections, the globe is transformed into a map by projecting a globe outward onto a cylinder.
Compass directions are depicted as straight lines, making these projections more useful for navigation.
Areas are stretched as the poles are approached, to the extent that the poles cannot be depicted.
The Mercator projection is a cylindrical projection.
Conical projections involve conceptualizing a cone over the globe. No distortion occurs where the cone intersects the globe.
In planar projections, the plane onto which the map is projected touches the globe in a single point.
1.10 - How Do We Use Maps and Photographs?#
Topographic maps were originally produced by sending a team of surveyors to take notes and sketch on paper. Today, these maps are produced directly from laser and radar measurements from orbiting spacecraft or from pairs of photographs taken at slightly different angles. These pairs are called stereo pairs, and a stereoscope can visualize the the images in 3D.
If a map produced is new knowledge, it is called primary data. A preexisting map that is used to provide input for answering some other question is called secondary data.
1.11 - How Do We Use Global Positioning Systems and Remote Sensing?#
GPS provides latitude, longitude, elevation, and velocity data from a constellation of 24 satellites sending signals to ground-based receivers.
Remote sensing refers to techniques used to collect data or images from a distance, including the processing of such data, and the construction of maps from such techniques.
In passive remote sensing, the sensor points at the area of interest and records whatever light, heat, or other energy is naturally is coming from that region.
In active remote sensing, an energy source directs a beam of energy downward or sideways toward the area of interest.
Energy-measuring techniques:
Visible and Near Infared (IR): Aerial photographs record the visible spectrum, but many photographs and satellite images also record adjacent bands of infared energy (near-IR).
Thermal Infared (IR): Measures the heat energy of the depicted area.
Microwave: Microwaves can penetrate clouds and haze, providing a clear view of the ground at all times. They can also measure the height of the sea surface and provide weather imagery.
Multispectral: Some satellites collect data at multiple wavelengths, and are therefore called multispectral.
Radar, Sonar, and Lidar: These techniques involve emitting waves of a certain wavelength and measuring how much is reflected back and how long it takes to return.
1.12 - How Do We Use GIS to Explore Spatial Issues?#
The process of taking an image or map and matching it to standard coordinates is called georeferencing or rectification.
We commonly call each map in a GIS system a layer.
Point-pattern analysis can evaluate the spatial distributions of data. This is done by comparing the distribution of points to a grid, and seeing whether is clustered, regular, or random.
GIS can be used for spatial interpolation, which involves comparing data at a location to known values at nearby locations.
1.14 - How Do Concept Sketches Help us Portray and Understand Features and Processes?#
A concept sketch is simple sketch accompanied by complete sentences that describe the features, processes, and interrelationships within a system.
The procedure for making a concept sketch is as follows:
Make a list of what to discuss
Decide what to sketch
Annotate your sketch