| Abstract
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A map of the Helena, Montana, vicinity was produced using a mosaic of 1990 black and white aerial photographs. ESRI ArcInfo and ArcView GIS were used to delineate vegetation cover types in the Helena, Montna, area for use by people interested in the preservation of open space and wildlife habitat. A total of 520 cover type polygons were delineated and labeled, used 24 different cover types. Potential wildlife and open space values of each type were discussed in a separate report.
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| Purpose
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The objective of the study was to produce maps of wildlife habitat and open space in the Helena area. As the value of wildlife habitat differs depending upon the wildlife of interest, and the definition of open space is, at best, rather tentative, a decision was made early in the project to map identifiable "cover types" in the study area. From these types, wildlife habitat and open space values were inferred.
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| Supplemental Information
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Black and white aerial photographs of the Helena area taken in 1990 were obtained from the Lewis and Clark Conservation District. The scale of the photographs was four inches per mile. Each photograph was scanned into a computer database (ArcInfo), corrected for distortion, and matched with neighboring photos to create a mosaic of 22 photos covering the study area. In addition, Xerox copies of the photographs were made for field use.
After creating the entire coverage, the database was converted to ArcView 2.1 for further analysis. Each photograph was brought up on the computer screen, and cover types were delineated by outlining a polygon (parcel) defining the outer boundary of that type. If necessary, an area on the photo could be enlarged in order to better identify the cover type. An attempt was made to delineate all cover type polygons five acres or larger. Once all polygons were delineated, the resulting theme was converted into a Geographic Information System (GIS) coverage (using Arc/Info). Next, each polygon cover type was labeled. Identification of the type was made using characteristics such as texture, location, slope and aspect, tone, etc. When necessary, the area of interest could be zoomed in on for a closer look, to find clues for identification. Broad types were field checked for accuracy.
A list of 29 cover types was developed that represented all types probably found in the study area. The differences between some of these types, such as between Developed-suburban, Developed-sub-division, and Sub-division/grassland, are subjective. The extent of development of these form a continuum, from completely developed to very little development. An effort was made to be consistent, but there may be areas of overlap where one polygon was identified as Developed-suburban, may in fact, be less developed than another polygon identified as Developed-subdivision.
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