Aerial Photograph
Definition
Aerial photographs are images captured from airborne platforms (e.g., planes, drones) that provide a top-down view of the Earth’s surface. They are classified as oblique (angled) or vertical (nadir) and can be analog (film) or digital. Used for mapping, surveillance, and environmental monitoring, they often serve as base layers in GIS.
Application
Aerial photography supports urban planning by documenting land-use changes over time. Environmental agencies use it to monitor deforestation, wetland loss, or coastal erosion. In agriculture, it aids in crop health assessment via NDVI analysis. Disaster response teams rely on post-event aerial photos to assess damage. Historical aerial imagery is digitized for heritage conservation or legal boundary disputes. Modern drones enable real-time, high-resolution surveys for small-scale projects.
FAQ
1. What distinguishes vertical from oblique aerial photographs?
Vertical photos are taken directly downward, minimizing distortion for precise measurements (e.g., orthophotos). Oblique photos capture angles for 3D context, useful for visual inspections of structures or terrain.
2. How do aerial photos differ from satellite imagery?
Aerial photos offer higher resolution (sub-meter) and flexibility in timing but cover smaller areas. Satellites provide broader, periodic coverage but may lack detail.
3. What are common distortions in aerial photography?
Relief displacement (tall objects leaning outward), parallax (shift due to perspective), and lens curvature. Orthorectification corrects these using DEMs.
4. Can aerial photos be used for 3D modeling?
Yes, overlapping photos (stereo pairs) enable photogrammetric software like Pix4D or Agisoft to generate 3D point clouds and digital elevation models (DEMs).