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Connect the points with the same Connect the points with the same valuevalue
Estimate between which other values Estimate between which other values the line should be drawnthe line should be drawn
Lines should be curved, not angularLines should be curved, not angular Extend lines to edge of mapExtend lines to edge of map Never cross isolinesNever cross isolines
Topography (Contour maps)Topography (Contour maps) 1-dimensional representation of a 3D 1-dimensional representation of a 3D
landscapelandscape Shows the shape of the landShows the shape of the land
Finding IntervalFinding Interval Difference between one contour line Difference between one contour line
and the nextand the next May be given on mapMay be given on map Labeled lines are Labeled lines are Index ContoursIndex Contours
Subtract the value of two consecutive Subtract the value of two consecutive Index Contour LinesIndex Contour Lines
Then count how many contour lines there Then count how many contour lines there are from one Index Contour to the next are from one Index Contour to the next (only count one of the Index Contours)(only count one of the Index Contours)
Divide the difference by the # of linesDivide the difference by the # of lines
300-200=100m
5 lines
100/5= 20m
HillsHills Hills or mountains are shown by Hills or mountains are shown by
contour lines that form closed loopscontour lines that form closed loops
Steep/gradual slopesSteep/gradual slopes Steep SlopeSteep Slope: contour lines are close : contour lines are close
togethertogether
Gradual SlopeGradual Slope: contour lines are far : contour lines are far apartapart
GradientGradient
Difference in ElevationDifference in Elevation
Distance between two pointsDistance between two points
Label with given units!Label with given units!
River DirectionRiver Direction
Contour lines bend upstreamContour lines bend upstream
Ocean is Sea Level = 0 elevationOcean is Sea Level = 0 elevation
Max: Value just below Max: Value just below what the next contour what the next contour line would equalline would equal
Z=Z= Min: Value just above Min: Value just above
what the next contour what the next contour line would equalline would equal
Y=Y=
•Z
•Y
99 ft
21 ft
Maximum ElevationMaximum Elevation
Represented by Triangle symbolRepresented by Triangle symbol
ProfilesProfiles
Cross section (side view) of the Cross section (side view) of the contour mapcontour map
Use mark and slide methodUse mark and slide method Keep a STEADY handKeep a STEADY hand No numbers on x-axisNo numbers on x-axis Use contour interval onUse contour interval on
Y-axisY-axis
What is the contour interval? 20What direction is Mud Creek flowing?