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Historical Airphoto Processing

Technical Overview Presentation

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Presentation Overview

Historical Airphoto Processing (HAP) SystemBackground – Historical Imagery

Traditional Approach – Correcting Historical Imagery

Value Proposition

HAP System – Details

Summary

BackgroundHistorical Imagery


Historical Airphotos - Background

Aerial photography records the ever changing cultural features on the Earth’s surface

Provide valuable information for a number of applications


Historical Airphotos - Applications

Environmental assessment– Wetlands, flooding, hurricane, earthquake

Climate change studies– Biomes, extents, coastlines

Land use planning– Expansion, densification, transformation, construction

Forestry management– Growth, clearing, re-planting

Oil & Gas– Wellhead sites, pipeline scars

Archaeology and Cultural Heritage– Conservation, restoration, demarcation


Historical Airphotos – The Need

Millions of historical (analog) airphotos exist in print or film form– If georeferencing can become cost effective, there

are a number of valuable uses for the imagery

Traditional approaches for orthorectifying historical airphotos are costly, time consuming and at times ineffective– Major manual effort to collect GCPs

Traditional Approach



Collect GCPs manually Standard automatic GCP collection techniques

are not well tuned

Usually requires 3-4 well distributed GCPs

Manual GCP collection is a major production bottleneck



What is the problem?

1. Automatic methods often fail Missing camera information leads to poor initial models

Poor image quality and initial georeferencing hinders automation

2. Manual collection is difficult and costly Manual GCP collection is a time consuming task

Land change can be significant

Scratches on film can create artefacts

Poor quality imagery makes it difficult to identify features


Poor Initial Georeferencing

941m (1882px)

Reference

Raw


Land Cover Change

1991


2011

Land Cover Change


Scratches and Damage


Poor Radiometry and Contrast


Scanning Artifacts


The Solution – PCI’s HAP System

Semi-automated solution for generating ortho-mosaics from historical airphotos

HAP SystemValue Proposition

HAP Value Proposition Increased Production• The HAP system can more than double production

capacity

Increased Efficiency• The multi-pass automatic GCP and Tie Point collection

reduces manual effort

High Accuracy• Accurate ortho-mosaics that often exceed the quality

produced by manual techniques• In many cases can handle poor interior model information better than

manual approach

HAP Features & Benefits

Features Benefits

Automated Fiducial Collection Reduced labor, high accuracy

Automated GCP/TP Significantly Reduced labor, high accuracy

Ortho-Mosaic – automated cutline and color balancing

High quality mosaics in less time

Works with multi-source and varying quality historical imagery

Rescue your valuable data

Some Metrics

Performance Information (Hours)Total Manual 2 15 3

Total Automated 16 46 4

Total Time 18 61 7

Accuracy Information (RMSE)Initial Accuracy 155m 254m +300m

Ortho Accuracy 5.7m 9.3m 5.8m

About DatasetsDataset 1 2 3Difficulty Easy Difficult Difficult

# of Images 266 278 50

Case Study

Project Details

Processing DetailsTraditional Approach HAP System

GCP Collection Manual Automatic

Tie Point (TP) Collection Automatic Automatic

Quality Assurance Manual (TPs only) Manual

Manual Labour (Hours) 24 8

Project Turn Around (Days) 3 Days 1.5 Days

- 130 raw aerial images acquired over a large urban area in 1954- Reference image of urban area acquired in 2011- Population grew by more than 10 million people between 1954 and 2011

Case Study

The same customer performed 7 additional tests over two areas in Asia Minor.

Case Study

Project # of PhotosProcessing time (Hours)

Accuracy(CEP 90)

001-1946 122 16.5 ± 8 m

001-1954 117 14.7 ± 6 m

001-1972 90 10.5 ± 6 m

001-1993 87 9.2 ± 5 m

002-1975 69 10.8 ± 7 m

002-1991 73 10.0 ± 6.5 m

002-1999 80 9.0 ± 5 m

Case Study

“All ortho-photo projects performed by the operator through conventional methods were found to be three times slower than the same processes performed on the HAP System.”

- HAP customer

HAP SystemDetails


26

HAP Interface

Consists of 3 easy to use panels

1123

Panel #1 Specify ingest parameters and

execute


27

HAP Interface


2123

Panel #2 Initial Georeferencing step panel


28

HAP Interface


3123

Panel #3 Coarse and Fine

Alignment panel


System Layout

Processing Systems QA/QC Machines

Network

Processing Systems for automated tasks QA/QC Machines for inspection and editing Simple network interface for accessing data

remotely


Workflow Overview

Innovative Multi-Pass Image AlignmentAchieve Ortho accuracy through iterative GCP and Tie Point collection

Manual Quality Check of GCPs and Tie Points

Processing tasks are highly automated scripts

Historical Airphoto Workflow

Data Prep Data Ingest

QA GCPs/TPs

QA GCPs/TPs

Coarse Alignment

Fine Alignment

Generate Ortho-Mosaic

Manual

Semi-Auto

Automatic

Optional Path


Data Preparation

Assess Input files• Input Images, Reference Image and DEM on Processing Machine

Create Metadata File • Can customize how ancillary information is fetched & assembled• Metadata only requires 5 pieces of ancillary information

Data Prep Data Ingest Coarse Alignment

Fine Alignment


Manual

Semi-Auto

Automatic

Manual

Semi-Auto

What is Data Prep…


Data Preparation


Fine Alignment


Manual

Semi-Auto

Automatic

MetadataAssess Input files

1. Focal Length

2. Approx. scene center coordinates or way to approximate them (i.e. flight-line)

3. Approx. flying height

4. Print dimension (i.e. 9” x 9”)

A custom script can often be developed

to assemble the data

1. All images part of a continuous block

2. All images in a given project have same fiducial mark (i.e. edge)

3. Appropriate DEM

4. Appropriate Reference Image (i.e. NAIP)


Ingest Data • Input imagery & reference data is read into HAP and converted to working formats

(PIX)• Calculate nominal Exterior Orientation

Collect Fiducial Marks • Automatic fiducial mark collection from a template image• Automation success depends on image quality

Data Ingest


Fine Alignment


Manual

Semi-Auto

Automatic

Automatic

ManualSemi-AutoAutomatic

What is Data Ingest…


Data Ingest


Fine Alignment


Manual

Semi-Auto

Automatic

Ingestion Process Initial Accuracy

• Ingest Data into working format (PIX)

• Calculate nominal georeferencing from scene centers and metadata

941m (1882px)

Reference

Raw


Coarse Alignment

Data Prep Data Ingest Fine Alignment


Manual

Semi-Auto

Automatic

Coarse Alignment

GCP Collection• Attempts to collect hundreds GCPs• Automatically removes statistical blunders

Bundle Adjustment• Automatic Tie Point collection and removal• Computes new math model (coarse model) often based on

100s of GCPs and Tie Points collected for each image

What is Coarse Alignment…Initial pass to improve positional and orientation accuracy

Automatic

Automatic

Control

Initial Alignment

Coarse Alignment


Coarse Alignment



Manual

Semi-Auto

Automatic

Coarse Alignment

Improved accuracy suitable for Fine Alignment run

GCPs & Tie Points Improved Accuracy

152m (304px)

Reference Coarse

• 10px < RMSE < 30px

• Evenly distributed GCPs/TPs

• Often very dense distribution

+ GCPs+ Tie Points


QA GCPs/TPs

QA Coarse Alignment



Manual

Semi-Auto

Automatic

Coarse Alignment

Review GCPs and Tie Points• Review distribution – Less important after Coarse Alignment• Identify “Island” subsets – Group of images tied together with no GCPs

If Required, Edit GCPs and Tie Points• Delete blunder GCPs & Tie Points• Collect GCPs on “Island” subsets

What does Coarse Align QA Involve…

Manual

Manual


Fine Alignment


Fine Alignment


Manual

Semi-Auto

Automatic

GCP Collection• Uses improved model from Coarse Alignment • Searches for GCPs with lower error

Tie Point Collection (Bundle Adjustment)• Searches for Tie Points with lower error

What is Fine Alignment…Create final model used to generate ortho images

Automatic

Automatic

Control

Coarse Alignment

Fine Alignment

Initial Alignment


QA GCPs/TPs

QA Fine Alignment



Manual

Semi-Auto

Automatic

Fine Alignment

Review GCPs and Tie Points• Review distribution – More important after Fine Alignment

If Required, Edit GCPs and Tie Points• Delete blunder GCPs• Prune and/or add GCPs to areas with poor distribution

What does Fine Align QA Involve…

Manual

Manual


Orthorectification


Fine Alignment

Manual

Semi-Auto

Automatic

Ortho Generation

Mosaic Generation

Mosaic PreparationGenerate

Ortho-Mosaic

Reference

OrthoHigh speed orthorectification

<0.5m (<1px)


Mosaic Preparation


Fine Alignment

Manual

Semi-Auto

Automatic

Ortho Generation

Mosaic Generation

Mosaic Preparation


Automatic Cutline Generation• High quality results• Retain mostly nadir imagery with cutline

constraints

Automatic Color balancing• Image Normalization (Hot Spot Removal)• Variety of high quality color balancing

algorithms


QA Cutlines and Color Balancing


Fine Alignment

Manual

Semi-Auto

Automatic

Ortho Generation

Mosaic Generation


QA Cutlines & ColorMosaic

Preparation

Multi-user Mosaic Editing• Multiple users can edit the same mosaic at

the same time from different computers

Advanced Mosaic Tools• WYSIWYG Viewer• Fast Redraw tools for cutlines• Manually adjust color balancing


Mosaic Generation


Fine Alignment

Manual

Semi-Auto

Automatic

Ortho Generation

Mosaic Generation


QA Cutlines & ColorMosaic

Preparation

Generate accurate seamless mosaics with OrthoEngine or GXL

HAP SystemSummary


The HAP System Summary

In response to market demand, PCI has developed new technologies to address the technical and operational difficulties of historical airphoto processing

Semi-automated approach reduces labour costs for large projects Iterative automatic GCP/Tie Point collection

Can double production Designed for taking in large projects 50-1000+

images per project


46

Find out more about HAP

Website

Historical Airphoto Processing Website

PDF Whitepaper

YouTube PCI Tech TV HAP Commercial Interview with Lead HAP developer

http://www.pcigeomatics.com/products/historical-airphoto

http://www.pcigeomatics.com/pdfs/HAP_WhitePaper.pdf

http://youtu.be/jd26YyaS3QM

http://youtu.be/ByHGEccnsOU

http://youtu.be/HAQG-DMLrPI

Private and Confidential

Contact PCI Geomatics

www.pcigeomatics.com

[email protected]

http://www.pcigeomatics.com/

mailto:[email protected]

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historical airphoto processing (hap) powered by geomatica

Technology

pci geomatics

hap interface

hap customer

manual collection

manual approach

hap system value proposition

historical airphotospage

costly manual gcp collection