U.S. Geological Survey Open-File Report 81–238
Landslides and Related Features, Pennsylvania [Warren
1- by 2-Degree Sheet]

General Notes on Imaging

The maps presented on this site were scanned from paper copies of the original maps, except for one quadrangle (Brookville), which was scanned from film (positive). The copies were provided many years ago by the U.S. Geological Survey, the publisher of this report. The quality of the copies varies, but it is generally fair to poor, largely due to the reproduction methods available at that time for hard-copy compilations. On many of the maps, the topographic and cultural base map is not visible or only faintly visible over wide areas, and the background is mottled and variably lighter or darker from one sheet to another or within various parts of the same sheet. Many of the original maps were spliced together within the map area, and these splice lines are noticeable on the copies as darker horizontal bands. In short, the images generally reflect the quality of the paper copies.

The maps were scanned in color (RGB) at 400 dpi and were saved in uncompressed TIFF format. Using raster editing software, the upper neatline of each map was rotated to horizontal, the images were converted to grayscale at 300 dpi, and the sheets were cropped to conform where possible to the edges of the paper copies. PDF files were made from the edited images.