All questions will be Multiple Choice Questions (MCQs).
Each question has five choices.
Only one correct answer for each question.
Some questions will involve selecting true or false statements.
The exam content will exclusively cover material discussed in lectures.
Content Review
Quick Review Session
Review of topics covered since the beginning of the semester, including geographic information systems (GIS) and their various components.
Key Areas of GIS Discussion
Functions of GIS:
Aspects include both hardware and software elements necessary for GIS functionality.
Measuring Locations:
Priority on accurate measurement of locations on the Earth's surface.
Emphasis on the science involved in measuring the Earth's shape.
Earth's Shape Models
Different models exist to represent Earth's shape:
Oblate Spheroid: Most accurate representation.
Circumference of Earth: Approximately 40 million meters.
Soids: Defined by semi-major and semi-minor axes used for modeling.
The purpose of using these models is to reflect Earth’s true shape more accurately at sea level.
Height Calculation
Different types of heights discussed:
Lowercase h: Represents the height of the object above datum.
Uppercase H: Represents the height above sea level.
Geometric Height: Relation between the different height measurements.
Height Calculation Formula:h=H+hgeom
Convert between height types based on given information.
Datum and Coordinates
Datum: Models Earth's surface through benchmarks.
Coordinates can vary significantly based on the datum used; offsets can be hundreds of meters apart.
Coordinate System: The zero meridian used to establish a geographic coordinate system (GCS).
Geographic Coordinate Systems (GCS)
Common GCS: WGS 84, established by the Greenwich Observatory in the UK.
Longitude Measurement: Longitude values differ slightly based on observational reference, leading to negative longitude values in practice.
Degree Conversion: 20 minutes is equivalent to approximately 1/3 degree or 0.333 degrees.
Distance Metrics
Estimation of distance based on latitude and longitude:
1 degree difference is approximately 100,000 meters near the equator.
Coordinate behavior at the poles where longitudes converge meaning distance becomes zero for points in the same location.
Coordinate Projection Systems
Geographic vs. Projected Coordinate Systems:
Geographic systems: 3D representation of the Earth.
Projected systems: Transform coordinates from 3D space to 2D.
Projection Methods:
Various types including equatorial, transverse, oblique projections.
Detail of the Universal Transverse Mercator (UTM) projection discussed alongside other systems.
Data Models in GIS
Two Common Data Models: Vector and Raster.
Resolution Concept: Refers to the size of the cell representing real-world dimensions.
Example of spatial resolution with remote sensing imagery indicates that a resolution of 30 meters captures a 30m x 30m square.
Data Handling
Discussion of converting various data types (numbers, texts) into binary format for computation.
Character Mapping Table: Each letter assigned a corresponding number, e.g., "a" maps to 65 in decimal.-
Data Redundancy: May increase data size; example given of elastic number.
Spatial Indexing Techniques
Spatial indexing is crucial for enhancing display speed and user experience within GIS.
Introduction to R-Tree indexing structures:
Methodology includes building rectangles around polygons to facilitate faster queries.
Limitations: Influence of user input during data digitization and boundary definitions.
Vector Data Generation
Use of remote sensing images in the creation of vector datasets like roads and buildings.
Data Errors vs Accuracy
Data Errors: Mistakes due to device malfunctions or operational errors.
Data Accuracy: Limitations due to the precision of measuring methods; reflects inherent uncertainties in measurements.
Geographic Information Storage
Considerations for data organization within databases:
Flat Data Representation: Rows for data records and columns for attributes, capturing various properties of datasets.
Definitions:
Database: A collection of data.
DBMS (Database Management System): A system managing data collection—functionality includes data entry, updates, and query execution.
Relational Data Models
Data organized into structured tables.
Use of SQL: Structured Query Language for data manipulation and retrieval.
Feature Class: Special term for categorized vector data.
Geocoding Process
Converting textual description into geographical coordinates:
Requires textual address information and reference data for effective geocoding.
Challenges in geocoding, e.g., certain addresses not yielding geographical coordinates.
Global Navigation Satellite System (GNSS)
GNSS Overview, referring to GPS:
Major components include:
Space Segment: Satellites in orbit.
Control Segment: Ground stations monitoring satellites.
User Segment: GPS receivers utilized by the public.
Accuracy Factors: Typical offsets in GPS time measurements leading to inaccuracies, addressed through adjustment variables (e.g., extdeltat).
Inverse Distance Weighting (IDW) Interpolation
Methodology of IDW:
Weight defined as the inverse of the distance between sampled points and target locations.
Define influence through a shear value, altering how distance affects interpolated values.
Practice examples regarding elevation values and distance modeling provided.
Decision-making processes on which points to include for calculations, utilizing fixed radius or maximum points approaches.
Conclusion
Summary of key GIS components and data measurement specifics, reinforcing concepts crucial for the understanding of geographic information systems and their applications.