AERIAL TOPOGRAPHIC MAPPING

This article provides a primer for engineers on aerial topographic mapping. Mapping companies will often state that the map will be created to National Map Accuracy Standards (NMAS). Understanding these standards is important, because sometimes maps compiled to NMAS may not be sufficient. In general, an aerial topographic map will be accurate to plus or minus half the contour interval vertically and plus or minus a quarter of the contour horizontally. Vibrations in the plane from taking off and landing can throw the camera out of calibration. Thus, mapping companies should calibrate their camera at least every 3 years and should understand how film behaves with their camera. A map's accuracy is directly related to how high the plane is above the ground. The photogrammetrist uses survey control points to set up the next model in the stereoplotter. Larger mapping companies use a method called aerotriangulation on projects with multiple models to reduce the number of ground control points. The advantage in using aerotriangulation is that bad control points are found immediately. The photogrammetrist can tell the surveyor what the correct coordinate is with amazing accuracy. Many other factors affect the accuracy of a map. One is the type of stereoplotter. There are two kinds: analytical and analog. For many reasons, analytical stereoplotters are far superior. Another element of a map's accuracy is the level of plan detail, which depends upon the plan scale accuracy the engineer specifies. The best way to specify for newer analytical stereoplotters is to require the map to be compiled so that all visible planimetric details are shown when it is plotted at a scale of 1" = 50' (2.54 cm = 15.24 m). To minimize shadow areas that obscure the ground a minimum sun angle of 30 deg (0.525 rad) and no cloud shadows should be specified. It is also important to specify a leaf off (trees and underbrush) condition when mapping.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/10519629
• Corporate Authors:

  Civil Engineering News, Incorporated

  1255 Roberts Boulevard, Suite 230
  Kennesaw, GA  United States  30144
• Authors:
  • Schork, R
• Publication Date: 2000-2

Language

• English

Media Info

• Features: Figures; Photos;
• Pagination: p. 52-58
• Serial:
  • Civil Engineering News
  • Volume: 12
  • Issue Number: 1
  • Publisher: Civil Engineering News, Incorporated
  • ISSN: 1051-9629

Subject/Index Terms

• TRT Terms: Accuracy; Aerial photogrammetry; Aerial photography; Aerial surveying; Altitude; Calibration; Cameras; Contours; Film; Mapping; Scaling factor; Standards; Topographic maps; Triangulation
• Identifier Terms: National Map
• Uncontrolled Terms: Aerotriangulation
• Subject Areas: Design; Highways; Planning and Forecasting; I21: Planning of Transport Infrastructure;

Filing Info

• Accession Number: 00788861
• Record Type: Publication
• Files: TRIS
• Created Date: Mar 7 2000 12:00AM