AGENDA #3a
BUDGET WORKING PAPER
TO: W. Calvin Horton, Town Manager
FROM: George Small, Engineering Director
SUBJECT: Cycle for Renewing Aerial Photography of Town’s Planning Jurisdiction
DATE: April 25, 2001
At the Council’s April 4, 2001 budget work session, a Council member requested further information about the cost and renewal cycle for renewing aerial photography of the Town.
The Town uses aerial photography as the basis for our Geographic Information System data displays. We also use aerial photography for site evaluations, impervious surface determinations, stream and Resource Conservation District delineation, engineering design, land use designation, and a variety of related uses.
The Town and the County have jointly contracted for aerial photography services in the past, in an effort to obtain economy of scale and lower unit mapping costs by creating a County-wide project for bidding rather than soliciting bids for only the Chapel Hill planning jurisdiction. Typically, Carrboro and the University of North Carolina also join in the contract, further lowering the Town’s net costs for the photography we are interested in obtaining.
The most recent flights were made during the winter of 1998-99, and included all of Orange County. The scale and detail of the finished aerial photography varies according to the needs of the users. For example, rural areas of the County are mapped at a scale of 1:400 with 5-foot ground contours. This level of detail is sufficient for general planning purposes. Alternatively, the Chapel Hill planning jurisdiction is mapped at a scale of 1:100 with 2-foot contours. This more detailed level of mapping is necessary for applications in urbanized parts of the County such as Chapel Hill.
It is necessary to re-fly the County periodically to update the aerial base-mapping in the Geographic Information System, and for the planning, engineering, and associated uses noted above. After considering our needs and discussing mapping update procedures with the State, County and Town staff agreed that a four-year cycle for re-flying and re-mapping was appropriate and would allow us to have reasonably current data to work with on a continuing basis.
The County is planning to establish a four-year cycle for new aerial photography, and we hope to continue contracting jointly with the County to achieve the best possible prices for the photography we are interested in obtaining. Based on past discussions with vendors, we would expect to pay as much as an additional 50% if the Town contracted separately to fly only our planning jurisdiction area, which would be a small job for most aerial mapping companies.
Based on the current contract, we estimate that the high resolution Chapel Hill portion of County-wide aerial photography contract will cost approximately $160,000. We propose setting aside $40,000 per year in the Capital Improvements Program to allow re-mapping every four years via a joint contract with the County. It is possible that the annual cost will change depending on our needs and technology improvements; but for now we think that setting aside $40,000 per year is the most prudent means for assuring that our base-mapping is kept reasonably current for all users.
We will re-evaluate costs and needs during each cycle, to assure that we are making the best use of available funds.