18-Geom-A7 Geospatial Information Systems · May 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2014 — 04-Geom-A7 Geospatial Information Systems. Closed-book; no calculator permitted. Format: twenty-three short-answer questions of equal value (5 marks each); a candidate answers any twenty, but all twenty-three 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); 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 conformal (orthomorphic) projection is one that preserves local angles and shape: at any point the scale is the same in every direction, so an infinitesimally small feature keeps its true shape and meridians and parallels intersect at right angles, exactly as they do on the globe. Conformality is a local property — small shapes are true, but areas are inevitably distorted, and the distortion grows with distance from the projection's line(s) of true scale, so large regions are not shape-true overall. Because bearings and angles are preserved locally, conformal projections are the standard choice for topographic mapping, navigation and any application where direction and angular relationships matter, which is why they underpin most national mapping grids. Examples of conformal projections include the Mercator projection (historically used for marine navigation because rhumb lines plot straight), the Transverse Mercator — the basis of the Universal Transverse Mercator (UTM) grid and the 3° MTM zones used for large-scale mapping in Canada — and the Lambert Conformal Conic, widely used for mid-latitude regions with a large east–west extent. In Canada, UTM (Transverse Mercator) is the workhorse conformal grid for GIS data.
