The first thing you need to do is specify the goal of the project. Are you planning on using the photographs to map the landscape? Or simply interpret or monitor something? Which features are of interest to you--vegetation, water, soil, geology? Your goals will determine the rest of the specifications. The State remote sensing/GIS department may be able to provide you with technical forms to assist you with the planning.

Next you need to determine the required scale, or ground coverage. If you choose a smaller scale, then there will be less photographs taken. The altitude limits for most commercial aerial survey firms is between 300 meters and 13,700 meters. If you desire to have more than one scale, it would be possible (and probably less expensive) to hire a firm that can use multiple cameras with different focal lengths rather than asking them to fly the same area at different altitudes. It is also a good idea to see if photography you can use already exists.

Now that you have determined the scale, you need to determine the season and time of day for the flights. The season depends on your project goals. If you are interested in finding deciduous trees, then you would not want to schedule a flight during the winter when the leaves have fallen. The time of day is important for 2 reasons: shadows and hotspots. If you schedule the flights for morning or late afternoon, when the sun is low in the sky, there will be many shadows in your photographs. It is also possible to acquire hotspots. Hotspots occur when the the sensor and sun and exactly aligned, and the result is a bright white spot in the photograph that hides all detail. These are due to the relative angle of the sun and the camera, and there are many tables to help calculate their avoidance (Heath 1973).

The last thing you need to do is plan the flight lines. This may be done in cooperation with the contracted firm. When planning the flight lines, you need a rough map of the area of interest. Depending on the shape of the area, you will choose the direction of the flights (i.e. north-south or east-west). You need to draw the flight lines so that there is an overlap of 20-30% on the sides of the images (sidelap), and the center of each photograph needs to be planned so that there is a 20-60% forward overlap (60% if your goal is steropairs to allow you to see the images in 3 dimensions). Below is an example of a flight plan produced by AUSLIG.

Once you have the project specifications, all you need to do is hire a commercial aerial survey firm. They will provide the cameras, film, labor, and any other necessary equipment to fulfill your needs. You should expect to find a firm using mapping cameras and able to provide the type of film that you want. The firm should be contacted at least 6 months prior to the planned flight dates so that there is time to finalize specifications, request lab work, etc.

Once the photographs are returned to you, they will overlap to produce something like this:

Heath, G.R. 1973. Hot Spot Determination. Photogrammetric Engineering 39: 1205-14.

Avery, T.E. and G.L. Berlin. 1992. Fundamentals of Remote Sensing and Airphoto Interpretation. 5^th ed. Upper Saddle River, Prentice-Hall, Inc.