ITC analysis of aerial images

• Introduction
• Aerial Sensor Technology
• Image needs for computer image analysis
• Synergy with LiDAR
• BRDF Correction and Normalization of Aerial Data Area
• Tests of feature-based BRDF correction curves on two flight lines
• Conclusion

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Conclusion

The ITC methodology has been successful at delineating tree crowns, assigning them species and regrouping them into forest stand polygons with data from numerous satellite and airborne sensors at a variety of spatial resolution around 50 cm/pixel. For each stand, the ITC-based information can be summarized and used to populate new attribute fields of the polygon, leading to information judged superior to that the conventional process. Volume, biomass, and carbon assessments, growth and yield models, etc., can all remain substantially the same. They will benefit from the additional precision. However, on the long run, they shall be replaced by models doing assessments starting from individual tree crowns.

Due to their large view angle and their less instantaneous acquisition (compare to satellite images), series of aerial images covering large areas require additional correction and normalization steps before their ITC analysis. Increased sidelap (overlap) areas and feature-based BRDF corrections and normalizations appear to offer a viable solution to these issues. However, additional care should also be taken while contracting-out for the acquisition of aerial images aimed for digital analysis.

As the bulk of the ITC analysis process can be made automatic (except the training of the species classifier), it should free-up interpreters to concentrate on the precision and the quality of the analysis: the number of species and situations that should be considered. Forest inventories with additional spatial details, increased precision, accuracy and timeliness may be within our reach.

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