Environmental Issues

Statement of the problem
The author presents a method of analysing visibility of land cover to produce results which can be used to assess changes in available resources

Significance of the problem
Some land cover features like mountains or cliffs can can remain unchanged for thousands of years. Others like forests and grasslands can change rather rapidly. Although natural processes play a significant role in shaping the land cover of an area, human activities are the leading force behind much of the land-cover changes taking place currently. Regardless of their cause, land cover changes may have a large impact on the ecological balance of an area as well as its economic productivity (Miller, 2000). Analysis of the land-cover patterns provides one of the ways in which experts assess and understand the resources in an area.

Literature material
Analysis and interpretation of aerial photographs taken over a range of years. As such, the author uses books and journal entries on remote sensing, cartography and photogrammetry. A host of books and journal articles on urban, rural and environmental planning also form part of the literature used for this paper.
Program guides like ERDAS IMAGINE and ESRI are also part of the literature used.

Approaches used
Aerial photographs of the area under study and taken between 1946 and 1988 were obtained.

The photographs were interpreted on the basis of 126 land cover features identified. Digital elevation models were produced to help record the heights of features such a forest canopies.

Visibility of the land-cover types was calculated for the area.

Findings
The author established that land-cover visibility studies could be used to study land cover changes taking place in an area under study. By assessing land-cover visibility in the area between 1946 and 1988, the author was able to observe the changes which had taken place in the area. They observed changes in the heights of features and sizes of woodlands, heather moorlands, and grasslands (Miller, 2001 100).

Implication
The findings of this study provide evidence for the suitability of land-cover visibility studies for resource studies and planning. It thus widens the range of choices of methods which planners and resource managers can employ to assess the resource situation and changes in an area.

Threats to the validity of the findings
The researchers had to rely on aerial photographs taken in the past. Since they had no chance of doing any ground-truthing to relate the aerial photographs with the situation on the ground, they had to rely heavily on their interpretation and analysis tools. However, elevation models are prone to many errors which may affect intervisibility. These errors result in lower or higher estimates of landscape visibility, thus compromising the findings.