07-10-2016, 02:32 PM
1458208286-introductiontotopomaps.ppt (Size: 2.42 MB / Downloads: 31)
Topographic Maps
Two dimensional model of the Earth’s surface (represents 3-D world)
Topographic maps are also known as contour maps.
Show elevation above sea level using contour lines.
Contour Line –
- line on a map that connects points of EQUAL elevation.
- show elevation and shape of the land
Relief – Difference between high and low elevations
Contour Interval –
difference in elevation between each line. MUST be equal spacing.
Contour interval =
20 feet
Rules for Contours
The maximum possible elevation for a hill is “1” less than what the next contour “should” be.
The highest possible elevation of the hill is just below the value of the next line that is not shown
Depressions
Contour lines which show a depression, crater, or sinkhole on a map.
Shown by dashed lines (hachure marks) on the inside of a contour line
The elevation of the first depression contour is the same as the lowest regular contour near it.
Rules for Contours
The lowest possible elevation for a depression is “1” more than what the next contour “should” be.
The lowest possible elevation of a depression is just above the value of the next line that is not shown
Gradient
A trail is four miles long as measured by the scale on a map. The beginning of the trail is at the 1,060 ft contour line and the end of the trail is at the 960 ft contour line. Calculate the gradient of the trail.