Geographic Problems Lecture 1-7

Geographic Problems (Lecture 1)

• Geographic problems involve location in the information or solutions
• Examples include forest management (cutting, replanting, roads), national park accessibility, and fertilizer application in farming.
• Three categories of geographic problems exist:
  • Scale (detail): Micro, Local (cities, parks), Regional (regions, epidemics), Global (global warming, pandemics).
  • Intent (purpose): Practical (urgent needs, money, emergencies), Curiosity-driven (less urgent, exploring phenomena).
  • Time Scale: Operational (efficiency), Tactical (short-term plans), Strategic (long-term goals).

Geographic Coordinates

• Geographic refers to Earth's coordinates (or any planetary system).
• Spatial refers to any coordinate system, including statistical data with spatial dimensions.
• Earth's system is a subset of generic space.
• Spatial coordinates are special as they include:
  • Dimensions (defining location).
  • Resolution (detail level).
  • Coordinate Systems (representing).
  • Topology (direction, distance, size).
• Spatial analysis involves all coordinate-related information.

Spatiotemporal

• Spatial progress in time (or vice versa).
• Temporal progress is often captured by comparing spatial snapshots taken along a timeline.

The Anatomy of GIS

• Hardware (increasing machine power; 2D, 3D, 4D limitations).
• Software (runs locally).
• Network (important for information spread).
• Data (digital representation of specified area aspects).

Geographic Attributes

• Nominal: No ranking, no equidistance, no absolute zero (e.g., county).
• Ordinal: Ranking, non-equidistant, no absolute zero (e.g., grades).
• Interval: Ranking, equidistant, no absolute zero (e.g., temperature).
• Ratio: Ranking, equidistant, absolute zero (e.g., concentrations).
• Cyclic: Ranking, equidistance, absolute zero (e.g., compass, Kelvin).

Geographic Data Representation (L2)

• Representations are digital models of Earth's surface aspects
• Simplification is vital for computer processing.
  • Spatial averaging (pixels with varying density).
  • Representing constant values over large areas.

Raster and Vector

• Raster: Divides the world into cells, each with an attribute value (e.g., satellite images).
  • Raster cells are squares generally that fit onto a surface, but distortion occurs when projected on Earth's curved surface.
  • Cells store a single attribute value, making them good for representing phenomena and statistical modeling. Raster representations are better suited for geographical models than vector representations.
• Vector: Curves are captured as points (vertices) connected by straight lines (common in geographic information systems).
• Vectors are effective for precise representation, including direction, distance, and ranking.
• Raster files (e.g., TIFF, JPG) and vector files (e.g., shapefiles, geodatabases) are used.

GIS Applications

• Mapping, Measurement, Monitoring, Modeling, Management. Maps cover a wide range of applications in the area of socioeconomic and environmental modeling, base mapping, and education. Examples of different GIS applications include but are not limited to the following.

Geodesy (L3)

• Geodesy studies Earth's shape, size, how to measure Earth's rotation and gravity, and continental drifts.
• A geoid is a model of a global average sea level that is perpendicular to gravity.
• An ellipsoid is a mathematical model of Earth, slightly flattened.
• Coordinates (longitude and latitude) are used to specify locations on Earth.

Projections

• Projections convert spherical Earth data onto a flat surface.
• Distortions are inherent in projections. Types include cylindrical (normal, transverse), Conic (tangential), and Azimuthal (tangential). Types of projection include Secant and tangent projections to minimize distortion.
• UTM is a widely used transverse Mercator projection.
• Local coordinate systems (e.g., Swedish Triangulated Grid, RT90) are used for specific regions.

Converting Geo-references

• GIS applications often involve converting projections and ellipsoids.
• Street addresses and place names can be converted to coordinates (geocoding).

Satellite-based Navigation and Positioning (L5)

• GPS (Global Positioning System), Glonass, Galileo
• Satellites orbit Earth, sending signals to receivers.
• GPS data types: Absolute (low precision), Differential, Statistical, and Network.

Equipment, Accuracy, and Cost

• Various equipment options (e.g., GPS receivers) exist to determine accuracy, cost, and overall performance.

Electromagnetic Spectrum

• Data are collected from the reflection in different wavelength bands
• Wavelengths are described from high frequency, high energy, and short wavelengths (Gamma, X-ray, to low frequency, low energy, and long wavelengths (radio waves).

Spectral Reflectance

• Reflectance of light across different wavelength bands.

Remote Sensing

• Multispectral use wavelengths (various colors) of light.
• Collects data in various bands, resulting in a summary of the reflection levels of different wavelengths.

The Visible Spectrum

• Visual light that we can see using photogrammetry technology.
• Different wavelengths are used for various data, including identifying vegetation, landcover, and infrastructure.

Cartography and Map Production (L6)

• Cartography is the art, science, and technique of making maps and charts. Formal maps: Reference maps (topographic) and thematic maps. Categorical/Map Production: Provides a useful tool for different types of maps for a variety of purposes.

Spatial Analysis

• Spatial analysis processes raw data into useful information (e.g., discovering patterns).
• Methods include queries, measurements, transformations, descriptive summaries, optimization, and hypothesis testing.

Spatial Interpolation

• A process of intelligent guesswork to estimate values of a continuous field where no measurements have been taken. common interpolation methods are thiessen polygons, inverse-distance weighting (IDW) and kriging.
• Inverse Distance Weighting and Kriging methods.