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How to Assemble Topographical Maps

A topographic map represents natural and manmade features that scale horizontal distances and vertical elevations. These maps determine the elevations of landforms and changes in elevation between points on the map by reading the contour lines. As the land surface changes a new topographic map is created or assembled using new elevation data.

Things You'll Need

Elevation data
Location data
Base map
Pen
Pencil
Eraser

Instructions

- 1
  Plot the elevation data on the base map at the corresponding locations with a pen. Use street maps or aerial photographs as a base.
- 2
  Find the lowest and highest elevations to help determine contour intervals. Contour intervals are the elevation units between each line on the map. Choose the smallest interval that adequately represents the data without overcrowding the map. For example, if the elevation's range is 0 to 10, the contour interval should be 1 or 2. If the elevation's range is 0 to 1000, the contour interval is 20 or 100. Contour intervals may be altered while creating the map to fit the data, but the internal must remain constant for the entire map.
- 3
  Draw the first contour with a pencil by choosing a center value and making a line across the map to connect points. The data that does not equal the contour line value lies to the side of the data point. For example, if the contour line is 50 and the contour interval is 10, then 52 is the closest. Line 55 is half way between lines 50 and 60, and 58 is close to 60, but on the same side as points 52 and 55. Keep in mind that values above 50 will be on one side of the line and values below 50 are on the opposite side of the line.
- 4
  Draw the remaining contour lines on the map using the initial contour line shape as a guide. Complete the map with one line below the data points and one line above the highest elevation. Label each contour with a value either on the ends or in the center. Keep labels consistent and readable without rotating the map.
- 5
  Smooth the contours by erasing and redrawing sharp angles and corners.
- 6
  Review the final topographic map to ensure it follows the contouring rules. Contour lines should not cross, touch, split or form branches. At streams, the contours should form a "V" that points upstream, and closed contours should represent hills and depressions. For areas with sparse data, estimate the contour line locations with dashes.
- 7
  Write the contour interval and horizontal scale on the map, so it's easy to recognize.

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