an approach for uav-based dsm filtering using image ... · filtering using image classification and...

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An Approach for UAV-based DSM Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron & Senior Research Fellow at RMIT email: [email protected] [email protected]

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Page 1: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

An Approach for UAV-based DSM Filtering Using Image Classification

and Geometric Constraints

Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron & Senior Research Fellow at

RMIT

email: [email protected]

[email protected]

Page 2: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

• Easy and fast deployment

• Low cost of operation for small sites

• Less prone to atmospheric effects

• Ultra-high resolution of up to 2 cm

• Good quality orthophotos and Digital Surface Model

• Ideal for mapping the natural environment

Page 3: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

Photogrammetric Processing Workflow

Multi-view Images

Geometric Alignment

Image Matching

Bundle Block

Adjustment

3D Point Cloud &

Orthophoto Generation

Automatic Aerial

Triangulation

Page 4: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

Spatial Product:Multi-spectral Orthoimagery

RBG overlaid on NIR mosaic at 4cm resolution

Image mosaic generated from 194 images

Page 5: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

Spatial Product: 3D Image

Page 6: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

UAV versus LiDAR

• High level of detail at pixel size density (1cm-4cm)

• No need for co-registration of LiDAR and Imagery

• Unlike LiDAR spectral information is available

• A fraction of LiDAR data aquisition cost

LiDAR UAV Point Cloud

Page 7: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

Accuracy Evaluation - Points outline Ground Control Points (GCPs): Red

Check Points (CKPs): Yellow

GCP No: 9

CKP No: 17

Page 8: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

Accuracy Evaluation - Points outline Ground Control Points (GCPs): Red

Check Points (CKPs): Yellow

GCP No: 9

CKP No: 17

Page 9: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

Accuracy Evaluation - Quantitative analysis

GCPs No 9

CKPs No 17

RMSE(∆E)(pl) 1.2

RMSE(∆N)(pl) 0.9

RMSE(∆H)(cm) 19

Image Resolution: 6cm pl: pixel E: Easting N: Northing

Random distribution of planimetric residuals

Page 10: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

DEM Generation - Point Cloud Processing

Above ground objects (gray) & Bare ground (brown)

• Major high differences indicate obove ground objects

• Window size should be greater than the size of the largest feature

• Average slope known

• Still misclassification exists

Page 11: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

DEM Generation - Image Classification RGB image mosaiec Clustring result Mask (red=1 & white=0)

• Unsupervised image clssification in 10 classes

• Merge classes to generate an image mask

• Point clouds on vegetation area are eleminated

Page 12: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

DEM Generation - Final Result RGB image mosaic DEM with geometry Image Mask DEM with combined

geometry & spectral

• Semi-automatic approach vs manual approach

• True DEM can be generated

• Other elevation products like Digital Canopy Model

Page 13: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

DCM Generation RGB Image DCM=DSM-DEM

Suitable dataset for tree stocking assessment and tree crown delineation

Page 14: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

Normalised DSM (nDSM) Generation

NIR Image

nDSM

Vegetation

Mask

Suitable dataset for building extraction

Page 15: An Approach for UAV-based DSM Filtering Using Image ... · Filtering Using Image Classification and Geometric Constraints Dr Mehdi Ravanbakhsh Remote Sensing Consultant at Astron

Thank you & questions?