18-Geom-A7 Geospatial Information Systems · May 2017
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2017 — 04-Geom-A7 Geospatial Information Systems. Closed-book; any non-communicating calculator permitted. Format: fifteen questions of varied value totalling 100 marks; fifteen questions constitute a complete paper and all fifteen are solved in full below. Most answers are required in essay form. Datum and coordinate conventions follow the Canadian spatial reference framework — NAD83(CSRS) horizontally and CGVD2013 vertically.
Reference texts: P. A. Longley, M. F. Goodchild, D. J. Maguire & D. W. Rhind, Geographic Information Systems and Science (4th ed., Wiley, 2015); P. Bolstad, GIS Fundamentals: A First Text on Geographic Information Systems (6th ed., XanEdu, 2019); P. A. Burrough, R. A. McDonnell & C. D. Lloyd, Principles of Geographical Information Systems (3rd ed., Oxford, 2015); M. Worboys & M. Duckham, GIS: A Computing Perspective (2nd ed., CRC, 2004); H. Samet, The Design and Analysis of Spatial Data Structures (Addison-Wesley, 1990); ISO 19115 Geographic information — Metadata.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
A DBMS (database management system) is software that stores, organizes, secures and provides controlled access to structured data, enforcing data integrity and supporting concurrent multi-user query and editing through a query language (typically SQL). In a GIS, a spatial DBMS (or geodatabase) extends an ordinary relational DBMS with geometry data types, spatial indexes and spatial operators, so that both the geometry (locations/shapes) and the attributes of features are stored and managed together in one system rather than in separate files. Using a DBMS gives a GIS: centralized, non-redundant storage; multi-user editing with transactions, locking and versioning; integrity and topology rules and attribute domains; security and access control; efficient spatial indexing (R-tree/quad-tree) for fast retrieval; and the ability to pose combined spatial-and-attribute queries in SQL. Example. A municipality stores its parcels in a PostgreSQL/PostGIS database, each parcel row holding a geometry column plus attributes (PID, owner, zoning, assessed value). A planner can then run a single spatial SQL query — SELECT pid, owner FROM parcels WHERE zoning = 'RES' AND ST_Intersects(geom, floodzone.geom) — to list every residential parcel intersecting the flood zone, while many staff edit the same data safely and integrity rules prevent overlapping parcels. This combination of spatial indexing, multi-user integrity and spatial SQL is exactly what file-based storage cannot provide, which is why enterprise GIS is built on a DBMS.
