Unit 5 (Midterms) Flashcards
- Vertical data (elevation, height) are the distinguishing characteristic of ___
Topographic maps
- Topographic maps show the configuration or shape and roughness of the ground; this roughness is commonly referred to as ___
relief
- involve all procedures, equipment and methods necessary to capture both horizontal and vertical data of points on the ground so strategically chosen to depict the terrain
Topographic maps
Modern topographic maps represent points that have identical elevations with lines called ___
contours
- These are idealized depiction from a side or oblique view
Sugar loaves
- The only form of topography on early maps (pre-1700) due to lack of detailed surveying
Sugar loaves
- Gives location of mountains/hills but not precise size
Sugar loaves
- use lines of varying width and length to depict slope steepness, drawn in direction of the slope. Initially unsurveyed and little better than sugar loafs
Hachures
the first form known giving general location of mountain ranges are referred to as ___
hairy caterpillars
- In modern maps, ___ are not often used except when the scale of the map is too small to permit contouring
hachures
- If properly drawn, they convey a good concept of the terrain, but their value is largely pictorial
hachures
- They were systematized in 1799 by Major Lehmann, an Austrian military officer, where line width became directly proportional to steepness. It hence became quite commensurable, but not very imageable: blank on top and in valleys, and shortly after a North-West light source was introduced to enhance imageability. This was the main type of relief depiction through the 19th century
hachures
- After accurately surveyed heights became available through the 20th century, ___ gave way to contours, but they are still used for very steep slopes such as cliffs, quarries and railway cuts, where contour lines would merge.
hachures
Disadvantages:
– Lack of absolute information
– Difficulty in distinguishing the direction of the slope
– Time-consuming to produce
– Obscures other information
– Not very effective except in mountainous terrain
Advantage
– They may show minor but important details otherwise lost on a contour map within the contour intervals
Hachures
came initially from the need to know exact depths in water, and were generated from a series of depths or soundings. The first ___ in the late 1900’s were on navigation charts as ‘isobaths’ (since hachuring was not suitable for an unseen landscape).
Contours
is essentially an isarithm or an isopleth: a line drawn on a map through all points having the same numerical value, as of a population figure or geographic measurement
Contours
– ___ (the distance between contour lines) is determined by terrain and map scale
Contour interval
– ___ are symbolized as wider lines and usually every 5th contour
Index contours
– ___ are approximate elevations (not accurately surveyed)
Form lines
– ___ (enclosing lower land) are drawn with small tick marks inside.
Depression contours
– A contour line must ___ split or divide.
never
– A contour line must ___ simply end except at the edge of the map.
never
– A contour line must represent only ___ elevation.
one
– A contour line may ___ intersect other contour lines. ___ are the only exception.
never; Overhanging cliffs
– Contour lines from a ___ crossing stream always points upstream.
V-pattern
– Closely spaced contour lines represent a ___, widely spaced lines indicate a ___.
steep slope; gentle slope
– Concentric circles of contour lines indicate a ___.
hilltop or mountain peak
– Concentric circles of hachured contour lines indicate a ___.
closed depression
Advantages
– it is the most commensurable (quantitative) method
– it is the origin for many (most?) newer depiction techniques, and it is now familiar to many users.
Disadvantages
– it is an abstract method (there are no counterpart to lines on ground); poorly suited to small scales
– less imageable but depending on: contour interval, map scale, landscape type, and users’ experience.
– These disadvantages were recognized early on and led to other methods being developed.
Contours
- The addition of colour to elevation levels, first tried as early as 1830. Color schemes require graduation, logical sequence, realistic colors, with the darkest still able to bear readable text.
Hypsometric tints
Advantages
– adds imageability, mostly at small scale; easily applied and understood
Disadvantages
– exaggerated terrace effect, no new real ‘information’ is added,
– differential contrast between tints and other elements, dubious color associations, (green with forest, etc.)
– which color scheme?.. chroma of the same hue, or spectrum range - green -> yellow -> red
Hypsometric tints
- This involves the addition of shadows to give the illusion of depth, assuming a theoretical NorthWest light source (at 45 degrees elevation). It was introduced in the 1900’s but became more widespread after 1960, with improved printing technology and user needs. It has become much more common with automation.
Shaded relief (hill shading)
Advantages
– highly imageable, continuous in appearance (as in reality), can show greater detail and character of landscape suitable over a variety of scales and as a general background for a variety of map types
Disadvantages
– Manually required artistic creation with pencil or air brush; It was costly and often poorly rendered, when done manually. It creates a variable background with some slopes very dark
Shaded relief (hill shading)
- This technique of applying a northwest light source to a contoured landscape was first tried in 1850 but printing methods then could not handle gray backgrounds (to be able to highlight illuminated lines).
Tanaka (relief) contours
- It was pioneered from the 1950s by Kitiro Tanaka who produced some exquisite examples using the theory of application of shading principles to contouring.
Tanaka (relief) contours
Advantage:
– the most imageable portrayal of landscape (3D), often used for ski hills and panoramas
Disadvantages
– the most time-consuming to produce with no consistent linear scale, (before computers)
Block (perspective) diagrams
Types of contours (5)
- Index contours
- Intermediate contours
- Supplemental contours
- Depression contours
- Approximate contours
- Shown as heavy lines, usually twice the gauge of the standard contours
Index contours
- Normally shown every fifth (5th) contour; carry the number or elevation designation
Index contours
- Lines of lighter weight between index contours; usually not labeled, except when the terrain is relatively flat; conform to the contour interval of the map
Intermediate contours
- In parts of the map where intermediate contours are closely spaced as to nearly unite or merge into a single line, it is customary not to portray the lines for short distances for readability (the technique is called ___)
feathering
- Used when the terrain is so flat and the intermediate contours are too far apart; drawn as dashed lines or lines of dots; usually drawn at one-half the specified contour interval of the map
Supplemental contours
- Used to show low spots around which contours close; index or intermediate contours are used to which ticks drawn perpendicular to the contour lines on the downhill side
Depression contours
- Used when contours cannot be drawn accurately possibly due inaccessibility of the area; based on the educated guess of the maker of the map
Approximate contours
constant vertical distance between two adjacent contour lines; is interrelated with the map scale
contour interval
___ intervals are appropriate for areas with light slopes and with small features such as hills
- Small
___ intervals are used for areas with steep slopes
- Large
the smaller the scale the ___ the contour interval
larger
- All points on any one contour have ___ elevation
the same
- A contour which closes within the limits of the map indicates either a ___
summit or depression
- Contours on the ground cannot cross one another except where an ___ is represented on the map.
overhanging cliff, a vertical ledge or wall
- Contours are evenly spaced on a ___
uniform slope
- Contours are straight and parallel to each other on a ___.
plane surface
- Irregular contours signify ___ terrain
rough, rugged
- The horizontal distance between adjacent contours indicates the ___ of the slope of the ground; the closer the contours, the ___ the slope
steepness; steeper
- Contours cross curbs and a crowned sloping street in typical ___
U-shaped curves
- Contours cross streams in a ___ pointing upward
V pattern
- Are made to determine the locations of natural, and cultural features on the earth’s surface, and to define the configuration of that surface
Mapping surveys
- On the maps include vegetation, rivers, lakes, oceans, etc.
Natural features
- The most common method of representing the topography of an area
- An imaginary level line that connects points of equal elevation
Contour lines
- The ration of the length of an object or feature on a map to the true length of the object or feature
Map scale
- A line connecting points of equal elevations
- Cannot be seen in nature
- On maps, represent the planimetric locations of the traces of level surfaces for different elevations
Contours
- The elevation difference between adjacent contours
- Depends on a map’s purpose and scale
Contour interval
- (rule) sharp-pointed V usually are in stream valleys, with the drainage channel passing through the point of the V, with the V pointing upstream
The rule of Vs:
- (rule) closed loops are normally uphill on the inside and downhill on the outside, and the innermost loop is the highest area
The rule of Os:
- Usually every fifth contour line is shown in a heavy wider line
Index line
The contour lines are physically followed on the ground using a total station
Direct method
No attempt is made to follow the contour lines
Indirect method
