Primary Control Network Survey Data
The City’s Survey Section is responsible for creating and maintaining the City’s Vertical Control network. When the City of Tampa migrated to NAVD 88 several years ago, the City Survey Section had already been involved in creating an entirely new vertical network. The Survey Section established “poured in place” concrete monuments every half mile within the City. These monuments are approximately 30” deep, 6” wide at the top and 8”-10” wide at the bottom (where possible). They have an 18” No. 5 iron rebar in the approximate center to facilitate recovery by ferrous locating instruments. The monuments were allowed to cure for a minimum of 6 months, and then a numbered aluminum disk was set into the concrete. Level runs were then performed both in a North and South direction and an East and West direction with each monument being observed on at least two separate closed level runs, performed by two separate crews. Where the Hillsborough River runs through the City, a third crew ran level runs crossing back and forth over the river to create a run to tie the two sides together with more redundancy. The network was adjusted in both NAVD 88 datum, and NGVD 29 datum as a convenience to local surveyors.
The network was subsequently published in a file that is usable in Google Earth and available for use by Engineers and Surveyors.
The Survey Section is in the process of updating the network to establish new monuments as the older ones are destroyed. The future of the network includes an update to Horizontal values in the future. The City of Tampa Survey Section is presently planning on continuing in the use of NAD 83/90 adjustment for its horizontal datum, and recommends all work done for the City of Tampa be done in that datum. Please visit the link below for the latest version of the network.
The network also received some acclaim and mention in one of our profession’s National Trade Magazines, The American Surveyor ©. Read about it here at http://www.amerisurv.com/content/view/11176/153/
The Primary Control Network Survey Data is available as a downloadable ZIP file. This can be extracted to a Google Earth Keyhole Markup language (KMZ) file.