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Scientific Investigations Report 2012–5167

Creation of Digital Contours That Approach the Characteristics of Cartographic Contours

By Dean J. Tyler and Susan K. Greenlee

Thumbnail of and link to report PDF (8.07 MB)Abstract

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

For additional information contact:
Earth Resources Observation and Science (EROS) Center
U.S. Geological Survey
47914 252nd Street
Sioux Falls, South Dakota 57198
http://eros.usgs.gov/

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Suggested citation:

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.



Contents

Abstract

Introduction

Characteristics of the Contour Generation Process

Cartographic Rules for Digital Contours

Practical Considerations

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

Pre-Processing Steps

Processing Steps

Locate Potential Problems

Post-Processing Steps

Resources Required

URL for Data Download

Contour Web Service

References

Glossary

Appendix 1. Contour Attributes Data Dictionary

Appendix 2. Abbreviations


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