Mapping Municipal Features of Bridgetown, Nova Scotia
Objective
The objective of the case study was to use ObliqueMapper to collect features of importance to municipal planners. Focus was given to the collection of double line roads, utility pole locations and building footprints.
Photo Acquisition
Photos were collected during the spring and acquired using a 10MP Canon EOS 40D with a 50mm lens from a Cessna 172 at an altitude of approximately 1000ft and speed of 140-160 knots. A total of 275 photos were acquired of which 7 were selected for orientation and digitizing. Image acquisition took a total of approximately 35 minutes including a 30 minute transit.
GCP Collection
Ground control points (GCPs) utilized for the case study had been collected earlier during a previous Bridgetown case study. A total 36 clearly identifiable locations were observed with a Trimble GeoXT during a 4 hour field visit. Each location was observed with the GPS for at least 1 minute, and post-processed against a local base station (15 km away).
Feature Collection
Over 250 features were digitized (roads, poles, lamps, building footprints, etc.) in ~25 hours. All features were then exported to Shapefiles for use within a GIS. Improvements to ObliqueMapper since this case study have substantially reduced digitzing times.
Results
Comparison of the resulting features with their real world counterparts reveals the power of ObliqueMapper to generate geographically and geometrically accurate features. No additional GIS editing of these features were required; unlike GPS data which often has random positional errors that need to be manually corrected.
