The short answer to this question is that there are many things that need to be considered when thinking about acquiring aerial photography for a community. Several states have agencies and guidelines that may also be useful. The important thing to remember is that the contracting and planning process is important and requires your time. Unfortunately, many communities have gone through problems in this area related to contract and the product deliverables. You might want to check with your state agencies to see if there is an existing imagery program that suits your needs. You may be able to use public data if it's available.
On the general side of the question, here are some of the questions you will want to answer.
1.) What will be the primary use of this imagery?
Is the imagery going to be used as a backdrop for other data, or will it be used to create new layers? This will help you to define what type of image accuracy and resolution you might need. If you are going to be developing new layers from the aerial imagery, you will want to know a lot about the exact accuracy of the imagery you are receiving. If you are using it as a backdrop, you will want to know its accuracy but may be less concerned about its range since you will not be creating new layers from it.
2.) What is an acceptable level of accuracy?
This relates to its use. How will you be using it and for what? What type of measurements are you going to be doing with the imagery? You will want to establish this and make sure to address it in your contracting. You will want to work out a way to check the accuracy of the product from a contractor. Do not assume that the accuracy number they give you has been validated. Independently validate the data, and make sure to budget time and effort into this in your cost estimates.
3.) When do you want to have the imagery flown?
You may want the imagery flown or planned during a meaningful time of the year. Some communities prefer times when the trees have shed their leaves to see the ground. Some communities prefer the timing to coincide with roads or infrastructure. Others have needs related to the season. In addition, your contractor may need to fly during specific windows. Make sure to identify your time frame for the flyover.
4.) Can you find cost-sharing partners?
The highest cost of imagery is putting the planes in the air — fuel, pilot, and equipment costs. Consider that you may want to see if any others in your area or neighboring counties are considering the same types of aerial imagery. It's cheaper to fly a larger area once than to fly multiple independent missions. You may also find that you can get mixed product at a reasonable price as opposed to just getting the high-resolution imagery for a smaller area — for example, imagery for the city limits at 1 foot and imagery for the rural areas at 1 meter.
5.) Why type of imagery product do you need?
Aerial imagery can come in many combinations of spectral bands. Most common are natural color, false infrared, and panchromatic. Prices may vary for each product. You may need to examine what your needs are for the data. For instance, you may want to have a panchromatic product of higher resolution versus an infrared product of lower resolution if what you mainly want is to see roads and buildings. Be sure to ask what different combinations a contractor might provide.
6.) Data licensing and maintenance: How will you share your data in your community? What types of licensing is there on the product? Your contractor may have restrictions on whom you share data with. You will also need to plan for the server space and back-up for keeping the data.
One of your best options is to visit with other similar communities and see what they have done with their imagery and how they acquired it. Look for a community with experience in the contraction and use of aerial imagery, or seek out someone who can help you in your state agencies. Aerial imagery can sometimes be costly, but it is usually a worthy endeavor if it suits your community's needs.
