Scientific Investigations Report 2012–5167
The capability to easily create digital contours using commercial off-the-shelf (COTS) software has existed for decades. Out-of-the-box raw contours are suitable for many scientific applications without pre- or post-processing; however, cartographic applications typically require additional improvements. For example, raw contours generally require smoothing before placement on a map. Cartographic contours must also conform to certain spatial/logical rules; for example, contours may not cross waterbodies. The objective was to create contours that match as closely as possible the cartographic contours produced by manual methods on the 1:24,000-scale, 7.5-minute Topographic Map series.
This report outlines the basic approach, describes a variety of problems that were encountered, and discusses solutions. Many of the challenges described herein were the result of imperfect input raster elevation data and the requirement to have the contours integrated with hydrographic features from the National Hydrography Dataset (NHD).
First posted August 20, 2012
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Tyler, D.J., and Greenlee, S.K., 2012, Creation of digital contours that approach the characteristics of cartographic contours: U.S. Geological Survey Scientific Investigations Report 2012–5167, 31 p. with appendixes.
Characteristics of the Contour Generation Process
Cartographic Rules for Digital Contours
Limitations of the Contour Dataset
Required Input Data
Input Data Quality Issues
Data Quality Issues in the NED
Examples of Errors and Artifacts in the NED
Examples of Errors and Problems in the NHD
Locate Potential Problems
URL for Data Download
Contour Web Service
Appendix 1. Contour Attributes Data Dictionary
Appendix 2. Abbreviations