Preparation of Forest Visitor map for rectification if originally in digital format Bitterroot, Clearwater, Flathead, Lolo, IPNF, Kootenai, Gallatin, Nez Pierce, Lewis and Clark, Custer
1. Convert Intergraph version of Visitor Map to .tiff. This is the "official" map that is distributed to the Forests, produced at 1000 DPI (dots per inch). 2. Use ERDAS Imagine to clip the map to the edge of the forest data (remove collar information). When processed, zeros are ignored and the .tiff image is converted to an .img image. The resulting image has a resolution of 3 meters. 3. Use the resulting image for rectification.
Preparation of the base coverage
1. Use the Region 1 quadrangle coverage (r1_quad24k, /fsfiles/unit/e/gis/library/fs_region1/quadrangles) for the Bitterroot, Clearwater, Flathead, Kootenai, Lolo, Helena, Lewis and Clark, and Custer NF's, and a combination of the R1 quadrangles coverage and the State of Idaho quadrangle coverage (quad75k, /fsfiles/ref/library/gis/idaho) for the IPNF, Nez Pierce and Gallatin NF's. 2. Select the appropriate quadrangles that cover the Visitor Map of interest. These are subset out in ARC Map to a shape file format. Using ARC Toolbox, the shape file is converted to a coverage; the resulting coverage has its projection defined and run through the BUILD utility. · Albers projection information - Datum: NAD 83 - Spheroid: GRS 1980 - Units Meters - Parameters: 1. Latitudes of 1st standard parallel: 46 0 0.0 2. Latitude of 2ed standard parallel: 48 0 0.0 3. Longitude of central meridian: -109 30 0.0 4. Latitude of origin of projection: 44 0 0.0 5. False easting at central meridian: 600000 6. False northing at origin: 0
3. Use this subset quadrangle coverage for rectification.
Rectification of Visitor Map
1. In ERDAS Imagine, bring up the subset version of the Visitor Map (.img). Select Geometric correction, Polynomial, set projection from GCP tool, use Vector layer for rectification. 2. Work around vector layer and set GCP points on the 7.5' tick marks identified by the quadrangle coverage. Make sure that the same area is selected on the visitor map. When setting the GCP point on the quad coverage set the map scale below 1:100. 3. After six points are identified, change polynomial to "2". 4. Place GCP points around the whole image. Save both the reference and input points. 5. Run the correction making sure that ignore zeros is checked. 6. Final orothorectified image is stored in the Regional library, by forest (/fsfiles/unit/e/gis/library/nf_forest name).