Landsat MSS imagery as an adjunct to aerial survey of Kangaroos
Study area selection
The study area for the overall project is centered on Goondiwindi is southern Queensland. Described in detail elsewhere (eg. Hill et. al. 1985, 1988, Hill and Kelly 1986), the area was selected to incorporate a major land use transition zone between predominantly crop land to the east and well wooded pastoral land to the west. An area such as this was suited to research into pest status of Kangaroos because of the high risk status of agricultural land adjacent to pastoral country. As well, the mosaic of land cover types typical of this region was an appropriate base of studies of habitat usage of kangaroos and favoured high kangaroo densities, facilitating research into aerial survey methodology.
Selection of a suitable region may be aided by a perusal of topographic maps; shire Hadnbooks; land systems reports; r the appreciation of the regional geography of the country that aerial survey practitioners develop for the areas they fly.
To optimize selection of areas with specific attributes, however, requires access to current, readily interpreted land cover and/or land use maps. Scale of the maps is also relevant as aerial survey is a regional tool compatible with small to medium scale cartography (generally 1.20,000 or smaller). In most cases such maps do not exists. Landsat MSS imagery, however, is ideally suited tot eh task, it provides a near real-time portrait of the landscape (16 day overpass cycle) and a single scene covers an area of 185 x 185 km. The segments of the spectrum recorded by the sensor assist in clear delineation of regional cover types although true-color images cannot be produced and this may prove confusing the new users. As long as the regional perspective is of interest the coarse spatial resolution of landsat MSS (80m pixels) is not a significant drawback.
In the work reported here, the non-standard Landsat scene 91/80A incorporates the study are. Even to the uninitiated in image interpretation, the pattern of land use is apparent on this scene. it should also be noted that a black and white, single band image at a scale of around 1/1,600,000 such as the one presented in
fig.2, is a poor substitute for a three band, color composite at larger scale. Standard, false color composites at a scale of 1/250,000 produced by ACRES were used to select the study area and aerial survey zones within it that suited the various research topics.
Figure 2. Landsat MSS, band 6, image for scene 91-80A recorded on 18 August 1985.
Aerial survey navigation
As is the case with many Kangaroo survey programmes, 1/250,000 topographic maps have formed the navigational base for the aerial surveys at Goondiwindi. However, at a survey altitude of 76m the raterhspars set of reference features plotted on these maps is not readily visible from the aircraft. Furthermore, the land cover and cadastral information recorded n top maps is often hopelessly out of date and may confuse the navigator and / or survey team. Maps from the study area, for example, are based on aerial photography from the early 1960's. While the sophisticated omega navigation systems now available on survey planes have eased the major problems related to locating specific points and following predetermined flight paths (transects), reliable, readily interpreted maps are still required for wildlife survey work from aircraft.
Landsat MSS colour composites at scales of 1/250,000 and 1/100,000 have proved ideally suited to the navigational tasks involved. These computer generated photographic products are available from ACRES and currently cost AU$ 310 for a 80 c 80 com image ( an additional master generation charge may apply). There is a comparative wealth of navigational cues available from land sat compared with the topographic map sheet. In addition, the clear differentiation between the land cover types and individual paddocks makes it possible to plot the positions of groups of Kangaroos on the imagery where distributional data are required at this level.
