what are the advantages of aerial photography over ground based data
Aerial photography allows one to see the "big picture". Depending on terrain, ground based surveys may be quite limited, whereas aerial surveys can cover a broad area at a time.
Aerial survey work can be completed quickly, while ground based teams may take a much longer time to cover the same area; consequently aerial work can be quite cost effective. Also, aerial surveys present a low level of risk to the surveyors, while actually being on the ground may expose them to a wide variety of natural risks; some areas many in fact be physically inaccessible to ground based researchers.
Aerial surveys do no damage. The area being examined is never touched, so there is zero impact from the survey process. Usually aerial surveys do not need to seek landowner permission, which can be a complication with on-ground work.
As technology has improved, aerial photography has become much more powerful. The photography can use wavelengths other than visible light, which can reveal variations in temperature, different species of vegetation, different mineral composition, and many other details that cannot be seen with the naked eye. The photographs can be uploaded for analysis and enhancement, and can easily be conjoined with other existing data to improve the overall survey.