18-Geom-A7 Geospatial Information Systems · December 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Paper format. National Exams, December 2018 — 04-Geom-A7, Geospatial Information Systems. Closed book (one approved Casio or Sharp calculator permitted); duration 3 hours. Fifteen (15) questions are provided and any ten (10) constitute a complete paper; each question is of equal value (10 marks), so a complete paper totals 100 marks. Most answers are essay-format; clarity and organization count. All fifteen questions are solved below for completeness.
Longley, Goodchild, Maguire & Rhind, Geographic Information Systems and Science (4th ed.); P. Bolstad, GIS Fundamentals (5th ed.); Worboys & Duckham, GIS: A Computing Perspective (2nd ed.); Burrough, McDonnell & Lloyd, Principles of Geographical Information Systems (3rd ed.); de Smith, Goodchild & Longley, Geospatial Analysis; OGC Simple Feature Access (ISO 19125); ISO 19157 Geographic information — Data quality; ISO 19115 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) What it is. Address matching (geocoding) is the process of converting a textual postal address — such as "12 Queen St W, Toronto" — into a map location by matching it against a spatial reference layer that carries address information. The geocoder first parses and standardizes the input (street number, name, type, direction, city, postal code), then finds the matching feature in the reference data. Most commonly the reference is a street-centreline network in which each segment stores a from–to house-number range for each side; the matched number is placed by linear interpolation along the segment (number 12 within the range 1–99 falls near the segment's start, offset to the correct side). Higher-accuracy references are parcel or building-point databases that give an exact point. Each result is a point feature tagged with a match score/confidence.
(b) Why it is an important vector analysis. A very large share of real-world information is recorded by address rather than by coordinates — customer and utility accounts, service requests, 911 calls, health and crime records, deliveries, business registries. Address matching is the bridge that turns this address-referenced tabular data into mappable vector point features, so it can enter a GIS at all. Once geocoded, the data become available to the full range of vector spatial analysis: mapping and hot-spot/density detection, buffering and proximity, spatial joins to other layers (which ward, which catchment), routing and service-area calculation, and site selection. It is intrinsically a vector operation because it works on a vector street network and interpolation and outputs vector points; it also underpins location-based services and emergency dispatch. Without geocoding, the majority of administrative data could never be located, mapped or spatially analyzed.
