18-Geom-A7 Geospatial Information Systems · December 2015
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — December 2015 — 04-Geom-A7 Geospatial Information Systems. Closed-book; an approved Casio or Sharp calculator is permitted. Format: twelve short-answer questions of varying value totalling 100 marks; all questions constitute a complete exam and are solved in full below. 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); J. P. Snyder, Map Projections — A Working Manual (USGS PP 1395); 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.
Georeferencing is the process of assigning real-world coordinates — a defined datum, coordinate system and projection — to a dataset so that every feature or cell occupies its correct location on the Earth. Its purpose is to bring all data into a common spatial framework so that independently collected layers register with one another and can be overlaid, queried and analysed together. Without georeferencing, a scanned map, an air photo or a CAD drawing is just an arbitrary array of pixels or local coordinates that cannot be combined with anything else; once georeferenced, the pipe layer, the parcel fabric and the orthophoto all line up on the ground, distances and areas can be measured in true units, and spatial operations such as overlay, buffering and proximity analysis return meaningful results. Georeferencing also lets the GIS transform between coordinate systems on the fly, so data captured in different projections can still be integrated. In short, georeferencing is what turns a picture into a map and makes spatial integration and analysis possible.
