22 - Proximal sensing 3

Proximal Sensing Overview

  • Last Lesson on Proximal Sensing: This lesson focuses on using different types of cameras for archaeological diagnostics.

  • Previous Lesson: Featured drone techniques, including flight realization, actual flight, and data processing.

Types of Cameras for Sensing

  • Panchromatic Camera: Commonly mounted on drones but limited to visible spectrum.

  • Multispectral Camera: Can capture different types of images beyond visible light, crucial for archaeology.

  • Infrared Bands: Particularly useful for obtaining relevant data in archaeological diagnostics.

Electromagnetic Spectrum Basics

  • Visible Light Range: Limited range from blue to red wavelengths.

  • Non-Visible Spectrum: Includes infrared, crucial for archaeological assessments.

Functionality of Multispectral Sensors

  • Data Acquisition: Captures multiple images, filtering light through narrow bands in both visible and invisible spectra.

  • Image Composition: RGB images are derived from separate bands (red, green, blue) including near-infrared.

  • Key Algorithm: NDVI (Normalized Difference Vegetation Index) for identifying healthy vs. stressed vegetation.

NDVI in Archaeology

  • Purpose: Identifies crop marks driven by differences in vegetation based on underlying buried structures.

  • Healthy vs. Stressed Plants: Healthy plants reflect more near-infrared; stressed plants reflect more red light.

  • Implications for Archaeology: Helps in recognizing buried structures affecting plant health.

Test Case Study in Precision Agriculture

  • Test Location: Kiwi plantation, summer 2020.

  • Observations: Areas of stressed plants identified due to irrigation issues; confirmed through multispectral imaging.

Thermal Imaging

  • Principle: Objects emit infrared radiation based on their temperature; higher temperatures emit more radiation.

  • Applications in Archaeology: Can detect human presence in low-visibility situations by highlighting temperature differences.

  • Historic Uses: Utilized during COVID-19 for remote temperature measurement.

Instrumentation Used

  • Camera Specs: Example of the used multispectral camera (6 optics for RGB and near-infrared).

  • Drone Compatibility: Original panchromatic camera removed to accommodate multispectral camera installment.

  • Drone Example: Phantom 4 drone used for flight operations.

Multi-Temporal Analysis in Archaeological Studies

  • Data Collection: Consistent image acquisition over time, relating to meteorological conditions and soil humidity.

  • Best Image Acquisition Timing: Optimal periods identified for clear visibility of archaeological marks.

  • Comparison of Conditions: Dry and moist conditions significantly influence the visibility of crop marks.

Seasonal Impact on Visibility

  • Testing Phase: Regular flights taken to observe changes in ground cover and archaeological visibility.

  • Dry Conditions Relationship: Visibility of archaeological markers better under dry soil conditions.

  • Green Coverage Influence: Dense vegetation can hinder visibility of anomalies in panchromatic images.

Conclusion

  • Multispectral imaging proven beneficial: In enhancing visibility of archaeological marks by evaluating health variations in vegetation.

  • Methodological Importance: Importance of understanding seasonal patterns and soil conditions for effective imaging.

Suggested Readings and References

  • Bibliography: Includes selections that could further inform students interested in multispectral imaging and its applications in archaeology.