LORAN-C: A Navigation Aid for Aerial Surveys

Abstract

We used an electronic long-range navigation aid (LORAN-C) in an aerial survey for moose (Alces alces) in southeastern New Brunswick. The survey required 24% less flight time than previous surveys using conventional navigation with map references. Reduced costs and increased efficiency and accuracy of aerial surveys make LORAN-C an important navigational tool for wildlife managers in coastal areas. J. WILDL. MANAGE. 53(1):228-230 Aircraft are used extensively to survey wildlife populations and habitat. The design of population surveys for ungulates usually involves following transects or intensively searching blocks of terrain (Caughley 1977). When aircraft are employed in population surveys, accurate navigation is essential. Navigation is difficult during aerial surveys over flat or featureless terrain, especially when flying at low altitudes. Winds also complicate accurate navigation. Navigation errors waste expensive aircraft time as pilot and navigator attempt to precisely establish their position. Most important, imprecise navigation violates an important assumption of aerial population surveys: aircraft must be on the transect lines or in the blocks that were selected when the survey was planned. Long-range navigation is an electronic aid to navigation that has been used effectively by fishermen and boaters for many years. The east and west coasts of North America and the Great Lakes are well serviced by LORAN-C transmitters (Patric et al. 1988). More recently, LORAN-C has become a popular navigational aid in aircraft. We report on the use of LORAN-C as a navigational tool to conduct aerial surveys of moose (Alces alces) in southeastern New Brunswick. Trans-Maritime Helicopters Ltd., Fredericton, New Brunswick provided pilots and the LORAN-C unit. We appreciate the helpful comments of D. M. Keppie on an early draft of the manuscript. STUDY AREA AND METHODS The Lakestream study area (46015'N, 65' 30'W) was in southeastern New Brunswick, approximately 160 km inland from the Gulf of Saint Lawrence, and within the Maritime Lowland Ecoregion (Loucks 1962). The study area encompasses 2,400 km2 of gently undulating plain with little relief. Elevations ranged from 30 to 122 m above sea level. We used a Bell 206 helicopter to estimate moose density during February 1984, 1985, and 1988. The authors were observers and navigators in all surveys; however, a different pilot flew each year. Survey protocol followed guidelines used in Ontario (Anonymous, Standards and guidelines for moose population inventory in Ontario, Ont. Min. Nat. Resour., Toronto, 17pp., 1981). Topographic maps (1:50,000) of the study area were overlaid with contiguous 25-km2 blocks. Corners of the 2.5x 10-km blocks corresponded to intersects of the 1,000-m Universal Transverse Mercator grid of the topographic maps. We selected blocks to be surveyed randomly and without replication in each year. Flights were planned to minimize ferry time between blocks. To ensure systematic coverage of each block, we drew 4 equally spaced transect lines through the longitudinal axis of each block. In 1984 and 1985, we transcribed forest logging roads and clearcuts onto the flight maps from the most recent aerial photographs as an aid to navigation and to help define boundaries of the survey blocks. In 1988, we converted the block coordinates and the start and end points of each transect line from the 1,000-m grid lines on the topographic maps to the nearest second of latitude and longitude. Geographic coordinates for the transect lines were entered into the memory of the LORAN-C unit (Apollo II, model 611, II Morrow, Inc., Salem, Oreg.) prior to each survey. The LORAN-C navigational unit determined a bearing and distance to each of the preprogrammed points and a visual refer-