final exam Flashcards
(93 cards)
1
Q
large scale vs small scale map
A
large scale = small places
small scale = large places
2
Q
what is a feature?
A
representation of a real-world object on a map
3
Q
What model is best for storing discrete data?
A
vector
4
Q
what is a table?
A
A database or file containing information about a set of geographic features
5
Q
line vectors have…
A
nodes on ends, vertices in the middle
6
Q
how does triangulation work for GPS?
A
GPS receiver measures its distance from 3 satellites (with known locations) to determine location of the receiver
7
Q
How does a GPS determine its distance from satellites?
A
time difference from when each satellite sends a code and the GPS receives it
distance = speed of light x time difference
8
Q
RGB 255, 255, 255 makes
A
white
9
Q
I am classifying Eckerd’s trees as “very healthy, healthy, some dead limbs, and dead”. What type of data is this?
A
ordinal (they are on a scale)
10
Q
In terms of rasters, what is “stretching” and why would I want to stretch an image raster?
A
What: extend the colors/shades of a raster so more is visible
Why: good for a rasters where most of the values are similar
11
Q
If you are making a map of population density, when would jenks classification be better than equal interval?
A
when trying to show differences in population density
12
Q
nominal data
A
names
13
Q
categorical data
A
groups
14
Q
ordinal data
A
in order (ex. poor, fair, good)
15
Q
interval data
A
has a scale with no meaningful 0
16
Q
ratio data
A
has a scale with a meaningful zero (no negatives)
17
Q
what is a chloropleth map?
A
thematic map in which a set of pre-defined areas is colored or patterned in proportion to a statistical variable (e.g. pop density per capita income)
18
Q
when would you symbolize using single symbol/color?
A
nominal
19
Q
When would you symbolize using unique values?
A
categorical and ordinal data
20
Q
when would you symbolize using graduated colors/symbols?
A
continuous data
21
Q
RGB vs CMYK
A
RGB makes white when all combined while CMYK makes black
22
Q
Modifiable areal unit problem (MAUP)
A
what: arbitrary aggregation units like states or counties may influence values = maps reflect influence of size not the data being mapped
how to fix: normalize by area, populations, etc. or use grids
23
Q
raster types: discrete
A
represents objects such as roads or land use (relatively few values)
24
Q
raster types: continuous
A
represents measurement that occurs everywhere (thousands or millions of potential values)
25
B&W maps
1) no more than 5 gray levels
2) use different patterns instead of colors
3) color balance rules still apply (mostly light patterns, emphasize small areas with dark ones)
26
What is a graticule grid and why would you use one?
what: shows coordinates like lat/long
Why: show where map is on globe
27
map objectives
1) how map will be viewed and why
2) what you want to convey
3) privacy issues
28
geographical coordinate system vs projection
GCS is unprojected data
29
what is a datum?
a way to fit a projection to the earth taking into account that earth us a spheroid and geoid
30
what projection type is used for polar regions?
azimuthal
31
mercator projection
most accurate at equator
- used for navigation
preserves: shape & distance
loses: area
32
cylindrical projections
distortion absent where cylinder touches globe (and increases as you move away)
preserves: shape & direction
loses: area & distance
33
conic projections
distortion absent at standard parallels (and increases as you move away)
preserves: area & distance
loses: direction & shape
34
azimuthal projection
distortion absent where plane touches poles (and increases as you move away)
preserves: area or distance
loses: direction & shape
35
what is a compromise projection?
- Sacrifices area, shape, distance and direction a little bit so that all are somewhat represented
- Usually used for maps of large areas (aka small scale) like all of the world
36
what are UTMs?
universal transverse mercator
- world divided into 60 zones that are 6 degrees wide
- distortion is minimal in each zone
- best for maps covering small areas in one zone
37
what is the state plane system?
states divided into one or more zones identified by unique FIPS numbers
38
define projection vs project tool
define projection: creates/changes only CS label (does not change coordinates)
project: changes coordinates in the file
39
When would you want to “define” a projection?
If you receive a shapefile or feature class and it has no information about its coordinate system
40
which item in a geodatabase is most analogous to a shapefile?
feature class
40
what is metadata?
Information about a data set that helps the user assess its purpose and quality
includes: tags, summary, description, credits
41
feature class vs feature dataset
feature class is within a feature dataset
42
shapefile vs geodatabase
shapefiles are spaghetti models while geodatabases are topological models
43
what does merging do?
two similar types of features are combined (results in combo table)
44
what does appending do?
adds additional features to an existing data set
45
what does it mean to dissolve?
removes boundaries of features with the same value in the specified attribute fields
46
what is a raster and why use them?
what: array of values in cells or pixels representing squares on the ground
why:
- better a storing certain kinds of data (elevation, images)
- better for analyzing certain kinds of data
- often faster analysis than vectors
47
what is a raster pyramid?
successively lower resolution copies are created by making 4 adjacent cells into 1 with each copy being efficient for different scales of display
- speeds up display of rasters
48
how do you georeference a raster?
identify pairs of ground control points visible in the raster and in a reference dataset -> transformation then calculates real world coordinates from the control point pairs and applies it to the raster
49
when are attribute tables created for rasters and what is in them?
when: discrete raster with limited number of unique values
what: value, count, and explanatory fields
50
two types of tables
1) standalone
2) attribute
51
standalone tables
- store tabular data
- not associated with spatial data
52
attribute tables
- store attributes of map features
- associated with spatial data layer
53
target vs join table
target receives info while join provides info
54
data types
1) short (whole numbers)
2) long (whole numbers)
3) float (decimals)
4) double (decimals)
5) text
6) date
7) BLOB (images, documents, etc)
55
what is a domain and what are the types?
rules about what can be placed in a field
1) range
2) coded
56
what is a range domain?
specify range of numeric values permitted
57
what is a coded domain?
provide lists of values to pick from
58
statistics vs summarize
stats provides stats on 1 variable while summarize would provide stats by subfield
59
what is a simple query?
allows you to chose a subset of things based on their attributes (e.g. select states with more than 1mil ppl)
60
What is snapping tolerance?
When the editing cursor falls inside the tolerance, it jumps to the precise location so the next point falls in the same spot
61
What are the advantages of using Auto complete polygon when editing?
- It eliminates silvers (gaps and overlaps)
- It produces a coincident boundary
- It is faster
62
In terms of GIS, what is topology?
what is on your map matching what is on the ground
63
When would end snapping be better than vertex snapping?
Ensuring that new streams connect to the ends of existing streams
64
If I wanted to select all buildings that are within 100 meters of Zeta pond, what would work best?
A spatial query
65
What is wrong with this attribute query: Building_name = Seibert OR James
SQL requires the field to be mentioned both times (Building_name = Seibert OR Building name = James)
66
If I had a feature class of all roads in Pinellas county and I wanted to end up with just the roads on Eckerd’s campus (and have none extend past the property line), should I do a spatial selection or a Clip. Explain why.
Clip is correct because I want the roads to end at our property line
67
AND vs. OR
AND = things that are both a & b
OR = things that are either a or b, but not both
68
I had a cave feature class and a states feature class. If I wanted a feature class that lists each cave, its attributes, and the state it occurs in, which type of tool would I use?
Spatial join
69
I have the range of the White Ibis and the range of the Glossy Ibis. I want a feature class of where these two species overlap and the attributes associated with each. Which overlay tool is best?
intersection
70
We have the country and the volcano feature classes. If I want to know which country each volcano is closest to I could do a spatial join.
What is the:
Target feature?
Join feature?
target = volcano
join = country
71
If I have a geology feature class and a soils feature class and I do a union, will I end up with more or fewer polygons?
more polygons
72
On screen “digitizing”
convert raster images into vector features by looking at the image loaded into the GIS and tracing each feature or object
73
dangles are created when
a node at either end is not connected to another line feature
74
interactive query
select with mouse
75
attribute query
specifies a certain condition based on fields in the attribute table and selects the records that meet the criteria
76
spatial query
select based on spatial relationships
77
oder of precedence (boolean operators)
evaluated from left to right
- parenthesis used to indicate what should be evaluated first
78
SQL stands for
structured query language
79
limits of spatial queries
- can only select entire features
- cannot specify boundaries (e.g. would select entire river, not just those/parts within a certain state)
80
cardinality
Each record in the target feature class can only have one row of information from the join feature class appended to it
81
2 basic cardinality approaches
one to one: each join feature will be copied once to the target feature class
one to many: creates copies of each target feature until enough are available to append with every matching join feature
82
union
combine all features in 2 data layers
83
clip
limit a feature class to just the extent of a shape
84
intersection
only want locations where the 2 data layers both occur
85
erase
removes portion of the input layer
86
buffer
delineate areas that fall within a certain distance of a set of features
87
dissolve
merge features when they share the same attribute value(s)
88
what is a sliver and how can you avoid them?
inaccurate boundaries or logical inconsistencies may produce small extraneous polygons or lines called slivers
Slivers can be minimized by specifying an XY tolerance during an overlay operation
89
how to increase topology when editing
Use tools like snapping, autocomplete polygon, split polygon
90
snapping
Automatically connects features -> moves the editing cursor exactly to the same point once it gets close.
91
dangle
when two lines fail to connect
92
What happens to area and perimeter/length when you use geoprocessing tools using feature classes in a geodatabase?
- Overlay often changes the shape, area, perimeter, and length of features
- The geodatabase fields Shape_Length and Shape_Area are automatically updated
- User-defined geometry fields, such as an ACRES field, must be updated manually using the Calculate Geometry Attributes tool
