Flordia Power & Light

Aerial and satellite imagery for mapping has been around for many years now. It is efficient and effective in producing maps that human hands never touch until the finished product is printed. But aerial and satellite imagery has never substituted for field surveying for utility facilities location. Locating facilities and terrain features has necessitated sending someone out into the field; a very time-consuming and expensive process.

Florida Power Corp., (FPC) of Juno Beach, FL, was faced with the need to quickly build a 12 mile transmission line from a substation to a new customer. They decided to try something different. FPC contracted with Lambda Tech International for use of their GPSVision digital imaging system, whodrove the proposed route of the line recording images of the terrain and facilities. These images were linked to GPS data that provided the location of items on the photographs to within 1 meter accuracy.

Lambda Tech’s GPSVision is a combination of hardware and software that allows a crew of one or two to drive a route in a van and record it in stereo images with the GPS locations along the route. The software then transfers those images and recordings to actually place the features on a map. Instead of a survey crew taking days to survey a 12-mile route, the Lambda Tech van can drive it at 35 to 40 mph while recording sterio images and finish the job in less than an hour.

The system consists of two stereo digital cameras mounted on a rack that fits on top of a minivan or truck. Included on the rack is a GPS antenna and solid-state inertial guidance system. One of the cameras is mounted above the driver’s head, the other above the passenger side.

“In Florida Power’s case, we made an image every 16 meters,” said a Lambda Tech spokesman. “The GPS data is stored as a digital record with each picture.”

Once the driving is completed, the data is returned to an office, the GPS data is differentially corrected and everything is written to a hard disk. The hard disk is loaded into Lamda Tech software running on a Windows NT client and feature extraction can occur.

The software brings up a map of the route, digital stereo images and a user-defined list of features to be captured. A data screen shows the feature position, name and user-defined attributes.

“As you look at the pictures, you can point with a cursor to anything within a 35-40 meter distance from the camera and accurately position it to within 1 meter or less on the surface of the earth,” Lambda says. “Data coming out of the feature-extraction software is already formatted for the target CAD or GIS system based on the specifications provided by the client. It’s really fairly simple since all the data collected can produce CAD and GIS files at a very fast rate. You drive, take pictures, process them and come back and make maps.”

In addition to positioning features on the landbase, the system also makes it possible to measure and record heights, widths and areas. “GPSVision is not a replacement for a survey, but it’s a big piece of the overall puzzle that needs to be done before a project starts,” says Rick Forbes, an FPC project engineer. “GPSVision allowed us to do in a few days what otherwise would have taken a month or more to do with a traditional survey. The GPS Vision product was helpful and unique with its combination of the drawing and visual elements of the finished product. The drawing gave us basically the same product we would have gotten with the survey. But the visual images also gave us an idea of what is out in the field-where we are in relation to a signal box or some other facility, a tree line, things like that.”

Time and money were the major savings of the pilot project says FPL’s Saleh. “It gave us the field data that we needed in a short a period of time as possible. It saved us money over conventional methods, but the real savings was in terms of time over surveying. In the future, if we are able to receive this type of information earlier in the route selection state, there could be a considerable amount of time and money saved.”

GPSVision already has been used to map more than a thousand miles of railroad rights-of-way for installation of fiber optic cable.

In Florida Power’s case, the data was transferred to AutoCAD format. However, it will support Microstation/MGE, ADE, Smallworld, Vision, MapInfo, and Arc/Info, as well as work with relational databases such as Oracle Informix, Sybase and Access. The system uses a 7400 GPS receiver built by Trimble Navigation Ltd. of Sunnyvale, Calif for positioning.