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Our Aerial Photography Applications

      • Point sources of pollution identification
      • Monitoring of suspended particles distribution throughout water bodies
      • Macrophyte progression monitoring
      • Terrestrial  habitat characterization and mapping


Like many other remote sensors, aerial photographic camera records radiance reflected from earth features. Unlike with most common digital imagers however, in photographic camera, this radiance is recorded in an emulsion of a photographic film at high resolution. Thus acquired data can be subsequently digitized and made available for computer analysis and processing. Aerial photographs are used for identification and monitoring of plumes of suspended solids, domestic or industrial wastes entering natural water bodies, oil spills, or lake eutrophication. Furthermore, airphoto interpretation is an effective technique for aquatic macrophyte, wetland, land cover and forest mapping and inventory (Lillesand & Kiefer, 1987). It has been successfully used for wildlife habitat mapping, classification and temporal habitat change monitoring. The advantage of this method is obvious. A complete picture of large tracts of land or water can be obtained. This results in increase of data acquisition accuracy, and enormous savings of manpower hours required for conventional ground sampling, laboratory time as well as data analysis.

Unfortunately, despite of its many possible uses and advantages, remote sensing seems to be rather underutilized (Roughgarden et al., 1991). This sometimes happens to detriment of many. For example, an $8,000,000 water intake for drinking water purposes was built in Lake Superior between Duluth, Minnesota and Superior, Wisconsin based on ground sampling without use of satellite imagery or aerial photography. The intake was constructed in an area exceeding the turbidity limits for drinking water 50% of the time. Aerial photos proved to be very useful during a law suit which resulted (Scherz and Van Domelen, 1973).


Lake and river management

Monitoring of plumes of suspended solids, domestic or industrial wastes entering water bodies, oil spills as well as lake eutrophication. Monitoring and management of aquatic weeds, and aquatic vegetation mapping.
Lac Brome, inlet G, Green filterInlet G, unsupervised classification
Lac Brome, Quebec, July 1993. Nearly vertical uncorrected airphoto of Elizabeth Ann-Beach bay just North of duckfarms. This photo was taken through a narrow band 500-550 nm filter (Kodak Wratten #99), from altitude of about 3000 feet. Narrow band green filter enhances the presence of light scattering particles suspended in inlet water. To the right is an unsupervised classification of the narrow band image.

Lac Brome, Inlet G, Yellow filterInlet G, classification of bottom features

Lac Brome, Quebec, July 1993. The same bay as above, shot a few seconds later through a wide band yellow filter. The photo shows the inlet bottom together with the bed of prevailing submerged macrophytes (Potamogeton spp.). The highest concentration of weeds shows yellow on the classified image.


Ecology and wildlife management applications

The principal goal of wildlife management is to maintain sustained populations of wildlife which includes game as well as non-game species, plants and their environment. It is a science built on natural history observation and conclusions from associations of wildlife population changes with environmental factors such as weather, habitat loss or harvest. Wildlife management is a discipline derived from the closely related science of ecology which could be defined as a scientific study of the interactions that determine the distribution and abundance of organisms (Krebs C.J, 1985). Wildlife ecology is therefore concerned with interactions between wildlife and their environment (habitat).

Throughout the evolution, various species of animals have adapted to various combinations of physical factors and vegetation. The adaptations of each species suit it to a particular habitat and rule out its use of other places. The number and type of animals that can be supported in a habitat are determined by the amount and distribution of food, shelter, and water in relation to the mobility of the organism. By determining the food, shelter, and water characteristics of a particular area, general inferences can be drawn about the ability of that area to meet the habitat requirements of different wildlife species. Wildlife managers must constantly monitor habitat for changes in its quality and quantity. They must be able to measure features of the habitat that relate specifically to the presence, number, or health of animal species in question. They must also ensure that the minimum requirements for maintenance of reasonable biodiversity are met. Because these requirements involve many natural factors, remote sensing techniques may prove to be an indispensable tool for wildlife habitat evaluation through mapping land cover, soil, forests, wetlands, and water resources analysis. Many surface features that are important elements of habitat, including vegetative species composition or density, and even biomass, can be interpreted and measured from remotely sensed data. The interspersion of habitat components, the length of edge and the distance to other critical habitat features can be measured on vertical images (Best R.G, 1983). The two most common aspects for which airphoto interpretation can most readily provide useful information are wildlife habitat mapping and wildlife censusing (Lillesand and Kiefer, 1987).

Wildlife biologists recognized the potential of remote sensing for decades. Dalke (1937) was the first to report the use of aerial photography for wildlife cover mapping. Leedy (1948) has published an article in the Journal of Wildlife Management, on the suggested uses of aerial photography in wildlife management. Unfortunately, the application of remote sensing in ecology and ecosystem management has not progressed as rapidly as the advances in remote sensing technology, and its potential still remains somewhat underutilized and unappreciated (Roughgarden J., 1991). There seem to be a couple of reasons for this. The apparent increase in complexity resulting from technological developments has led to decrease in acceptance and use by ecologists and wildlife biologists (Best R.G, 1983). Afterall, remote sensing is a multidisciplinary science which requires a reasonable knowledge and understanding of processes involved. Secondly, there exists some perception that the costs involved are formidable. This view may actually be justified when one considers the acquisition cost of the latest, state of the art high-resolution imaging spectroradiometers or radar sensors. It may be comforting to know however, that satellite remote sensing data is sold on the per scene basis, and that the cost per area covered is actually cheaper than the cost of aerial photography. Furthermore, volume of literature describes the use of inexpensive small and medium format aerial photography for a successful high spatial resolution data collection (Clegg and Scherz,1975; Adams et al.,1977; Curran P.J., 1981; Best R.G, 1983; Lillesand and Kiefer, 1987.

Recently the trend has been toward the use of satellite data or combination of satellite imagery and aerial photography (multistage concept of remote sensing); reason being larger area, and repetitive coverage at cost lower than that of large format aerial photography. Unfortunately, this advantage is inevitably offset by lower spatial resolution of satellite imagery as well as higher noise/signal ratios. Another problem with imagery aquired by sensors located on space-borne platforms is the cloud cover. The use of satellite imagery together with aerial photography offers the best of the two worlds. It provides wide coverage at reasonable cost, yet, areas where higher detail and spatial resolution is required are flown at the time of the satellite overpass to provide the necessary spatial resolution needed.

Many state and provincial government agencies produce habitat inventories based on computerized classification of satellite data and aerial photography interpretation. The interpretation criteria for distinguishing between different classes are similar on both types of imagery. Water bodies have the lowest reflectance resulting in the darkest tones with little or no texture on the imagery. Rivers and streams can be identified by dark tones and a linear meandering shape. They may have light tones if they carry heavy loads of  sediment. Forested land also appears as dark tones on black & white imagery. It can be distinguished from water bodies by its mottled texture. Forested land has deep red tones on color infrared imagery. Cultivated land is easily interpreted by the regular shapes and patterns of fields. Tone and color will vary depending on the crop type, phenology and density. Fallow fields may have very dark tones, but this is variable and depends on the soil type and surface moisture. Rangeland can also have variable tones but generally has a less defined shape or pattern than agricultural land. It may show slight textural differences if there are pronounced vegetative density differences, or if shrubs are present. Urban areas are distinguished by the regular patterns of buildings, parking lots, roads and streets (Best R.G, 1983).

Marsh, October 1997
Philipsburg bird sanctuary, Philipsburg, Quebec. A mosaic of four vertical aerial photographs taken from an altitude of 3300' ASL in October 1997
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