Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
57 Cards in this Set
- Front
- Back
|
Map scale equation
|
map distance/ground distance
|
|
|
large vs. small scale
|
large= more detail, smaller area
small= less detail, larger area *the smaller the scale is, the lower the % is that it will be accurate *smaller scale means fewer features |
|
|
Q: how many inches on a map is 20 miles on a 1:100,000 scale map?
|
1/100,00=x/20
-cross multiply and get x by itself -then convert miles to inches |
|
|
Cartographic accuracy
|
what we can physically see on the map
|
|
|
positional accuracy
|
-tested against something
-actually going out and standing somewhere the GPS says there's a tree and seeing if there actually is and how far off it is from the map |
|
|
MMU
|
(minimum mapping unit)
-when mapping, if an area is less than MMU, it is merged into a larger unit *more detail with smaller MMU |
|
|
Datums
|
mathematical model estimating shape of spheroid
-has a set of precise control points which help define a base control system to have least amount of distortion |
|
|
3 types of datum
|
NAD27
NAD83 WGS84 |
|
|
NAD27
|
-based on clarke1866
-"middle" was meades, KS |
|
|
NAD83
|
-based on GRS spheroid
-"middle" was center of earth |
|
|
WGS84
|
-GPS is based on this type of datum
-uses GRS80 spheroid |
|
|
types of projections
|
planar
cylindrical conic |
|
|
planar
|
representation of sphere or ellipsoid on planar surface
|
|
|
cylindrical
|
round earth in cylinder
|
|
|
conic
|
round earth in cone
|
|
|
round earth on flat map distorts..?
|
-distance
-shape -direction -area -angles |
|
|
planar/azimuthal
|
-tangent or secant
-3 light sources |
|
|
3 light sources of planar/azimuthal
|
gnomonic
stereographic orthographic |
|
|
gnomonic
|
light source is center of earth
-least amount of distortion b/c it's a straight line -shortest distance is closest |
|
|
stereographic
|
-light source is opposite side
-preserves shape |
|
|
orthographic
|
-light source is infinite
-"truest" direction |
|
|
standard parallel
|
the lines that intersect the earth for a secant projection
|
|
|
3 secant orientations
|
equatorial
transverse oblique |
|
|
equatorial standard parallels
|
axis is parallel to earth's rotation
|
|
|
transverse standard parallel
|
axis is 90 degrees to earth's rotation
|
|
|
oblique standard parallel
|
axis is at any other angle than parallel or 90 degrees
|
|
|
Conformal projection
|
preserves shape
|
|
|
equivalent projection
|
preserves area
|
|
|
compromise projection
|
preserves neither shape nor area
|
|
|
2 popular types of projection
|
Albers equal area
-preserves area Lambert conformal -preserves shape |
|
|
area on earth --> type of projection
|
near equator --> cylindrical
mid-latitude --> conic polar region --> planar east/west --> conic north/south --> transverse cylindrical |
|
|
Coordinate systems
|
standardized method for assigning codes
|
|
|
types of coordinate systems
|
geographic (*NOT a true grid)
cartesian UTM military grid state plane *the rest of these ARE true grids |
|
|
geographic
|
- not a true grid
- latitude and longitude - uses decimal degrees |
|
|
decimal degrees
|
46 degrees 15 minutes 36 seconds
-->46 + 15/60 + 36/3600= 46+.25+.01 [46.26] |
|
|
cartesian coordinate system
|
-2 points- straight line difference
-find the distance with Pythagorean theorem (x=easting y=northing) |
|
|
UTM
|
-projection AND coordinate system
- tangent along central meridian - split into 60 sections of 6 degree widths so each section is its own coordinate system to accommodate for less distortion |
|
|
state plane
|
- each state divided into 1 or more zones
- each zone with its own coordinate system - horizontal= lambert conformal conic -vertical= transverse mercator |
|
|
digital cartography
|
presenting spatial info digitally
|
|
|
map
|
real world model where features are replaced by symbols
|
|
|
7 map requirements
|
1- title
2- map figure 3- legend 4- scale 5- north arrow 6- source block 7- neat line |
|
|
inset and locator maps
|
inset map is more detailed and zoomed in than a locator map
|
|
|
types of map data
|
discrete
continuous nominal ordinal ratio interval |
|
|
discrete
|
specific # of fractions at one point
|
|
|
continuous
|
a continuous measurement
|
|
|
nominal
|
-tells you A is different from B
-derived from qualitative |
|
|
ordinal
|
-differentiated by class/rank
-derived from quantitative -"small, medium, large" |
|
|
interval
|
-ordinal or rank data WITH values
-based on an arbitrary scale -0 IS arbitrary *you can have 0 for a temp value, or an elevation |
|
|
ratio
|
-based on an arbitrary scale
-ordinal or rank data with values -0 is NOT arbitrary *you can't have 0 as an age, or an area, or a precip value.... it simply doesn't exist at that point |
|
|
natural breaks
|
look for breaks in data
|
|
|
manual
|
you enter interval width data
|
|
|
equal interval
|
diff. b/w lowest and highest value (range)
pick # of classes and it interval is determined -they'll have equal widths unlike natural breaks method |
|
|
defined interval
|
pick interval and it gives you the # of classes
|
|
|
quantile
|
-arranges data from low to high
-equal # of observations in each interval |
|
|
arithmetic
|
class width increases at an arithmetic (additive) rate as it goes up
|
|
|
geometric
|
widths of classes increase in size at an exponential rate
|
|
|
projection properties summary
|
3 surfaces (planar, conic, cylindrical)
3 light sources (gnomonic, stereographic, orthographic) 3 orientations (equatorial, transverse, oblique) contact points (tangent, secant) distortion patterns |
