Aerial Photo Interpretation
& Georeferencing
Locating Vulci's Hidden Treasures from Above
Aerial Photo Interpretation in Vulci
Images taken by a drone or from an airplane are combined combined and processed through software that uses a least squares regression method to create a single plane that represents the surface of the Earth and shows high resolution imaging (up to a couple centimeters of accuracy) of the whole area. This is useful for seeing the relationship of areas that have already been excavated and how these monuments relate to each other, but also for crop marks and other signs of untouched monuments underground that could be subject for future excavations.
Georeferencing
Georeferencing is the step before aerial photographs can be interpreted. It is the process of giving an image coordinates that match an area in the real world. The process goes as such:
1. Take image from drone or airplane.
2. Physical presence at the site of interest is needed. Using an antenna pole, we could do one of two things: gather GPS points at specific locations marked by paper targets or create a shape file (which basically GPS points put on a digital map, but with no reference to positions in the world). In basic terms, a shape file is a vector layer that can be overlaid on a base map imported as a raster.
3. Use software to combine GPS points/shape files and images. Software used can be ArcGIS or QGIS. In the software, we import the image as a raster image to act as the base map. A base map has two meanings: it can either be an already georeferenced image that will serve to georeference further images by comparing the two or it can be an image that we are trying to georeference. The shape file/GPS points are then inserted as a vector layer and manual comparison of the layer and the base map is needed to create a georeferenced image.
4. Annotate images for photo interpretation. These annotations are saved as vector layers on the map and can be represented as lines or polygons. In the images above, the annotations are done as lines. If they were polygons, the spaces inside the squares would be filled in.
Images taken by a drone or from an airplane are combined combined and processed through software that uses a least squares regression method to create a single plane that represents the surface of the Earth and shows high resolution imaging (up to a couple centimeters of accuracy) of the whole area. This is useful for seeing the relationship of areas that have already been excavated and how these monuments relate to each other, but also for crop marks and other signs of untouched monuments underground that could be subject for future excavations.
Georeferencing
Georeferencing is the step before aerial photographs can be interpreted. It is the process of giving an image coordinates that match an area in the real world. The process goes as such:
1. Take image from drone or airplane.
2. Physical presence at the site of interest is needed. Using an antenna pole, we could do one of two things: gather GPS points at specific locations marked by paper targets or create a shape file (which basically GPS points put on a digital map, but with no reference to positions in the world). In basic terms, a shape file is a vector layer that can be overlaid on a base map imported as a raster.
3. Use software to combine GPS points/shape files and images. Software used can be ArcGIS or QGIS. In the software, we import the image as a raster image to act as the base map. A base map has two meanings: it can either be an already georeferenced image that will serve to georeference further images by comparing the two or it can be an image that we are trying to georeference. The shape file/GPS points are then inserted as a vector layer and manual comparison of the layer and the base map is needed to create a georeferenced image.
4. Annotate images for photo interpretation. These annotations are saved as vector layers on the map and can be represented as lines or polygons. In the images above, the annotations are done as lines. If they were polygons, the spaces inside the squares would be filled in.