GIS Exam 4 (Final)

Geographic Information: 

• Information about places on the earth’s surface 

• Knowledge about “what where when” 

• A system for managing spatial data and associated attributes 

• Allows for searches on geographic objects  

• Generated views of these spatial objects (maps) 

Systems: GIS- What's the S?

The technology for the acquisition and management of spatial information 

Science-: GIS- What's the S?

• The concepts and theory behind the technology  

• Comprehending the underlying conceptual issues of representing data and processes in space-time 

Studies: GIS- What's the S?

• The societal context 

• Social, legal, and ethical issues associated w/ GISy and GISc 

Computer Cartography:

The science, technology and art or making maps using computer and other new technologies 

1950 UNIVAC:

UNIVersal Automatic Computer was the first commercial computer produced in the United States 

1980 GBF/DIME:

Dual Independent Map Encoding (DIME) is an encoding scheme developed by the US Bureau of the Census for efficiently storing geographical data. The file format developed for storing the DIME-encoded data was known as Geographic Base Files (GBF) 

1990 TIGER:

Topologically Integrated Geographic Encoding and Referencing, or TIGER, or TIGER/Line is a format by the United States Census Bureau to describe land attributes such as roads, buildings, rivers, and lakes, and census tracts (FIRST US DATABASE 1990) 

Computers & GIS: 

• Faster, Easier, Cheaper 

• Computer graphics for map drawing & increase accuracy of geographic info 

• New survey technology for map update  

• Computer data transfer via mobile storages and networks for map sharing  

• Computer graphics and plotting/printing 

• More significant digits (precise) 

• Easy coordinate adjustment (Geocoding) 

• Easy overlay and visually compare geocoded maps to one another 

 

GIS Software Timeline:

Arc Info → Arc View → Arc Map → Arc GIS → Arc Pro 

What have computers done to GIS/ Cartography: 

• The design loop: Ideate --> select --> prototype --> evaluate  

• Cheaper storage and faster processing 

• The birth of analytical cartography & GIS 

• Early GIS systems = computer mapping programs plus a few data management functions 

GIS Definition- USGS

A GIS is a computer system capable of assembling, storing, manipulating, and displaying geographically referenced information  

GIS Definition- Tomlinson (1972)

The common ground between information processing and the many fields using spatial analysis techniques 

All GIS definitions

All definitions recognize that spatial data are unique because they are linked to maps  

*A GIS at least consists of a database, map information, and a computer-based link between them 

Roger Tomlinson:

Recognized as the “father of GIS,” he is the visionary geographer who conceived and developed the first GIS for use by the Canada Land Inventory in the early 1960s 

GIS World Model: (data slices) 

• Imagery 

• Elevation 

• Transportation  

• Addresses 

• Boundaries 

• Water Features 

• Survey Control 

• Your data 

Multi-Criteria Area Model:

• Spatial decision-making process used to identify the most suitable to least suitable area based on multiple factors of criteria 

 

What questions GIS can help answer? 

• Location (Where) 

• Condition (What) 

• Trends (How is it changing) 

• Pattern identification (What spatial patterns exist_ 

• Modeling (What if?) 

Raster Maps: 

• Maps created by PIXELS 

• Each cell location has an X and Y value (horizontal & vertical) 

• Each cell/pixel has a data value (elevation) 

• Cells/pixels have real size 

Vector Maps: 

• Represent POINT, LINE, POLYGON accurately 

• Line and points created by X and Y Coordinates 

• Allows high precision 

• More attractive map 

Data Structures: 

• A table of attribute information 

• Linked to locations 

• Columns are attributes 

• Rows are features (or Records, generally) 

 

Spatial Data (Where?):

Location and geometry (point, line, polygon, raster) 

Attribute Data (What?):

Characteristics/ details (name, area, pop, land use) w/ units 

GIS System Architecture and Components:  

Data input → Geographic Database → Query/ Transformation/ Analysis → Output: Display and reporting (map) 

ArcGIS: 

• Environmental systems research institute 

• Leader in desktop GIS 

Idrisi: 

• Named for Arabic geographer Muhammad al-Idrisi 

• Originally rater based  

• Built as a not-for-profit system  

GRASS/QGIS: 

• GRASS-Originally developed by US Army Corps of Engineers 

• Open-Source collaborative GIS  

• FREE 

TransCAD 

Transportation

Other Popular GIS Software’s

• MapInfo 

• GeoMedia 

• Maptitude 

What GIS applications do:

manage, analyze, communicate 

Automation of activities involving geographic data 

• Map production 

• Calculation of areas, distances, route lengths 

• Measurement of slope, aspect, viewshed 

• Logistics: Route planning, vehicle tracking, traffic management 

Integration of data with maps, communication of complex spatial patterns  

Environmental sensitivity 

Answers to spatial queries 

Access to emergency vehicles 

Preform complex spatial modeling  

What-if modeling for transportation planning, disasters planning, resource management, utility design  

What GIS applications do: manage, analyze, communicate 

1. Automation

2. Integration, communication of complex spatial patterns

3. Spatial queries

4. Spatial modeling

Why Study GIS: 

• 80% of local government activities estimated to be geographically based (zoning, public works, land ownership) 

• State government has geographical components (natural resource & highways/ transportation) 

• Businesses use GIS for applications 

• Military and defense 

• Scientific research employs GIS 

Tobler's First Law of Geography: Auto correlation in GIS

The closer something is, the more similar the data (measures how much nearby spatial data points resemble on another) 

Vector data

Focused on modeling discrete features with precise shapes and boundaries 

• Uses points stored by their real (earth) coordinates 

• Lines and areas are built from sequences of points in order  

• Lines have a direction to the ordering of the points 

Raster data:

Focused on modeling continuous phenomena and images of the earth 

• Data redundancy 

The GIS Database 

• In a database; store attributes as column headers and records as rows 

• The contents of an attribute for one record are a value 

• A value can be numerical or a text 

Geographic reference: 

• Must contain a geographic reference (43.8133°N, 91.2331°W) 

• The GIS cross-references the attribute data with the map data, allowing searches based on either or both  

• The cross-reference is a link  

 

Attribute data:  

• Attribute data are stored logically in flat files  

• A flat file is a matrix of numbers and values stored in rows and columns, like a spreadsheet 

• Both logical and physical data models have evolved over time 

• DBMS’s use different methods to store and manage flat files in physical files 

 

Vectors and 3D: 

• TINs model 3D surfaces using triangle/edge topology 

• Use Delaunay triangulation of irregular point data 

• Common in CAD and surveying applications 

• Efficient vector-based method for surface interpolation 

• More compact and precise than grids for terrain modeling 

Strengths and limitations of Vectors: 

• Accurately represents point, line, and area features 

• Efficient storage and processing compared to grids 

• Required for TIN-based volume modeling 

• Works well with digitizers and pen/line plotters 

• Not ideal for continuous surfaces or area-filling plotters 

 

Vector data formats: 

• GIS can import or convert many data formats 

• Common formats: industry standard, shapefiles (.shp) 

• Vector formats preserve real-world coordinates 

• GeoPDFs are becoming more widely used 

• True vector formats: DLG, TIGER (topographic data) 

Data Structure Exchange (Within GIS Systems): 

• Most GIS platforms use one primary data structure 

• Users manage conversions if multiple structures are supported 

• Vector → Raster is easy; Raster → Vector is harder 

• Structure conversion needed when switching tools or models 

GIS Data Exchange (Between Systems) 

• Data sharing via export/import can cause attribute or geometry errors  

• Standards help: 

• FGDC → metadata 

• OpenGIS → format interoperability 

• Format conversion has improved, but challenges remain 

• Efficient exchange is key for long-term GIS usability  

What is Metadata: 

Data dictionary; documentation that describes the content, quality, condition, and other characteristics of a data set (data about data) 

• Does not include actual data sets 

• One metadata record per data set 

Data Sources: 

• Using existing data 

• Data Creation:  

  • Geocoding- conversion of spatial information into a digital form 

    • Involves capturing the map/ attributes 

    • Necessarily involves coordinates; often address matching 

Geocoding methods for geospatial data: 

• Assigns coordinates to address features 

• Measure the map- scanning & digitizing 

• Measure the earth- field data & collection 

• Adds a ‘stamp’ on data- Influence the structure and error associated with the spatial information  

Georeferencing:  

• Aligning geographic data to known coordinate system so it can be viewed, queried, and analyzed with other geographic data.  

• Involves shifting, rotating, scaling, skewing, warping, rubber sheeting, or orthorectifying data 

Orthorectification: 

• Corrects distortions in images caused by terrain elevation and sensor tilt 

• Removes perspective errors, making distances and features geometrically accurate 

• Essential for mapping in topographically diverse areas 

Digitizing:  

• Captures map data by tracing lines from a map by hand  

• Uses cursor and electronically sensitive tablet 

• Result is a string of points with (x, y) values 

• Selecting points to digitize 

  • Fewer where points are straight 

  • More where line is curvier  

  • More reference points than just the beginning and end 

Create point data from lat/long 

• X field (Longitude) 

• Y Field (Latitude) 

• Z Field (Elevation) 

Address Matching: 

• Most GISs contain capability  

• Matching data with existing address database 

• Plotting data from XY points 

Raster files

• JPEG/ JPG 

• PNG 

• TIFF/GEOTILES --> adobe photoshop 

• ERDAS = ~5mB  

• ENVI = ~20mB 

Vector files

• TIN 

• DXF 

• Shape files (.shp)- Arc View –MOST POPULAR 

• e00- Arc Info 

• .aprx/ .gdb (geodatabase)- Arc Pro–REPLACING 

Remote sensing:  

The acquisition of information about an object without being in physical contact with it- Charles Elachi 

CORONA:

Americas first satellite program, occurring been (1959-1972), but the American public did not know until 1995- declassified to assist scientists w/ environmental studies  

Civil Remote Sensing in the US: ERST-1 (Aug 1972):

• First civil satellite 

• Equipped with Return Beam Vidicon and Multispectral Scanner 

• Renamed Landsat 1 when series started First civil satellite 

Civil Remote Sensing in the US: 

• Other satellites: DSMP, GOES (same time period) 

• 1980s: Commercial satellite launches 

• Late 1990s: Massive expansion of remote sensing capabilities 

 

Energy Source: Passive

Uses sunlight (e.g., Landsat) 

Energy Source: Active

Sends its own signal (e.g., LiDAR, RADAR, SONAR) 

Interaction with EM Radiation 

• EMR (light) interacts with Earth's surface 

• Wavelength ↔ Frequency: 

  • Long wavelength = low frequency 

  • Short wavelength = high frequency 

Atmosphere

Affects how radiation travels to and from the target 

Target-

Surface reflects or emits energy depending on material 

Recording Device-

Sensor captures reflected/emitted energy 

Transmission & Processing-

Data sent to ground stations and processed into usable formats 

Interpretation

Analysts extract meaning (e.g., vegetation, land use, water) 

Application-

Used in fields like agriculture, mapping, disaster response, etc. 

What is being detected? 

• Electromagnetic (EM) radiation 

• Day- reflected solar radiation & emitted radiation 

• Night- emitted thermal radiation 

• Contrast w/ other geophysical techniques  

Day

reflected solar radiation & emitted radiation 

Night-

emitted thermal radiation

The Electromagnetic spectrum: Visible light spectrum

400-700 nm 

True Color Composite: (additive/ multiband) 

• 400-500 nm = Blue 

• 500-600 nm = Green 

• 600-700 nm = Red 

• Absorbs All = Black 

• Reflects All= White 

Subtractive:

Cyan, Magenta, Yellow, Key (Black) 

Continuous data:  

• Elevation 

• Temperature 

• Precipitation 

• Reflectance (light) 

Categorical Data: 

• Land Cover Type  

• Soil Type 

• Vegetation Type 

 

EM Radiation: 

• Wave and particle interpretation  

• The basic particle of EM radiation is the photon 

Fundamental processes:  EM Raditation

• Emission: The ‘birth’ of photons (all bodies above absolute zero emit EM radiation) 

• Absorption: The ‘death’ of photons 

• Scattering: The life’ of photons (directional changes- reflection, refraction) 

Atmospheric Windows for Remote Sensing:  

Wavelength with high amount of transmission and little absorbance 

• Variation in atmospheric transmission with wavelength of EM radiation, due to wavelength-selective absorption by atmospheric gases 

• Only wavelength ranges with moderate to high transmission values are suitable for use in remote sensing 

Remote Sensing Platforms- Spaceborne

• Satellite constellation 

• Space Shuttle SAR 

• Satellite Multi-Hyperspectral SAR 

Remote Sensing Platforms- Airborne

• Airborne Multi-Hyperspectral SAR LIDAR 

• Aerial Photography 

Remote Sensing Platforms- Ground-based

UAV (drone) Hyperspectral LiDAR Optical  

Sun-synchronous polar orbits: 

• Near-polar path; Earth rotates beneath 

• Global coverage with repeat, fixed-time sampling 

• Altitude: 500–1,500 km 

• Ex: Landsat, Terra, Aqua 

Non-Sun synchronous orbits: 

• Flexible over tropics, mid/high latitudes 

• Variable revisit times 

• Altitude: 200–2,000 km 

• Ex: TRMM, ICESat 

Geostationary orbits: 

• Stays fixed over one region (continuous view) 

• Covers low-mid latitudes, ideal for weather 

• Altitude: ~35,000 km 

• Ex: GOES 

Remote sensing: Passive → Optical

• Panchromatic 

• Multispectral 

• Superspectral 

• Hyperspectral 

Remote Sensing: Passive → Air photos

• Photo interpretation 

• Photogrammetry 

Remote Sensing: Active

• Radar 

• LiDAR 

Passive: RM

• Use natural energy sources: Sun or Earth 

• Sunlight: 0.4–5 µm (visible to shortwave infrared) 

• Earth/Atmosphere: 3 µm – 30 cm (thermal IR to microwaves) 

Active RM

• Emit their own energy 

• Radar: mm to meter wavelengths 

• LiDAR: UV, visible, near-infrared 

Remote Sensing (Matrix) Data Format: 

• Each pixel = brightness value (reflectance) 

• More reflectance = higher value (brighter) 

• Typical range: 8-bit (0–255) 

  • White = 255 

  • Gray = 127 

  • Black = 0 

• Image resolution = based on number of pixels 

Photo interpretation:

The act of examining aerial photographs/images for the purpose of identifying objects and judging their significance 

Photogrammetry:

The science or art of obtaining reliable measurements by means of photography  

Resolution: All the remote systems have four types of resolutions  

1. Spatial

2. Spectral

3. Temporal

4. Radiometric

Spatial Resolution: (what area and how detailed) 

• Describes how detailed an image is 

• Measures the smallest object or distance a sensor can distinguish 

• High spatial resolution vs. low spatial resolution

High spatial resolution

more detail (e.g., 1 m) 

Low spatial resolution

less detail (e.g., 30 m) 

Spectral Resolution: (what colors-bands) 

• Refers to the number and width of wavelength bands a sensor can detect 

• Determines which "colors" or EM bands are recorded 

• Muti-spectral Remote Sensing 

  • Multiple bands (red, green, blue, NIR)  

  • Useful for vegetation, land use, water studies  

• Panchromatic Band:  

  • Broad single band (200-700nm) 

  • Captures grayscale imagery in 1 channel