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Results

Applications

CASE STUDY: City of Saint-John, CanadaHistorical Mosaics and Digital Elevation Models

Final DSM

Processed PhotosRaw Photos

Results

1967 1982

Learn more about HAPwww.pcigeomatics.com/hap

Through the HAP automatic workflow, historical aerial images from 1967 (183 images) and 1982 (64 images) were processed into an ortho-mosaic and Digital Elevation Model. The deliverables attained a positional accuracy less than 5 meters in relation to the reference imagery. Previous attempts to correct the same imagery at the City of Saint John yielded results with poor radiometric quality and low positional accuracy. Through the use of the HAP system, we produced the mosaics in a matter of days, with superior color balancing and positional accuracies. These mosaics have been added to the City’s internal enterprise GIS layers and also made available to the public through the City of Saint John’s Open Data initiative.

• Environmental Assessments• Civil Law/ Litigation• Bylaw Enforcement• Real Estate Evaluations• Land Cover and Vegetation• Natural Hazard Risk Assessment• Land Settlement Measurement• Forestry Growth Assessment• 3D Feature Extraction• 2D Feature Extraction• Environmental Remediation

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The Historical Airphoto Processing (HAP) system offers an automatic approach consisting of three main processing steps (Data Ingest, Coarse Alignment and Fine Alignment). Ingested imagery approximate scene centres are derived using available information, which is then further improved through the collection of Ground Control Points and Tie Points. The multipass alignment approach generally provides positional accuracies of 5 m or better, depending on the reference imagery used and elevation models for the orthorectification processing. Further processing can be accomplished once the images are correctly positioned, including orthorectification, mosaicking and also DEM extraction.

Methodology

The Historical Airphoto System (HAP) system offers an automatic approach consisting of three main processing steps (Data Ingest, Coarse Alignment and Fine Alignment). Ingested imagery are provided approximate positioning that is further improved through the collection of Ground Control Points and Tie Points. Over the multi-alignment approach, proper spatial accuracy is achieved enabling further processing steps - such as Orthorectification, mosaicking and the generation of elevation models. The city of Saint John, located in the province of New Brunswick covers a land area of 3,362 square kilometres and has a population of 126,000 people. This case study describes how historical airphotos from 1967 and 1982 were converted from scanned images to orthorectified mosaics and digital elevation models (DSM’s) covering the entire city. The results from this project are published in the city’s website: https://goo.gl/p3kGCC

Introduction