Term
| What is snapping and why is it important when editing docs? |
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Definition
Snapping allows you to create features that connect to each other so your edits are more accurate, with fewer errors. When snapping is turned on, your pointer will jump, or snap to, edges, vertices, and other geometric elements when your pointer is near them and within a certain tolerance. This enables you to position a feature easily in relation to the locations of other features.
Snapping is useful with many editing operations, such as creating polygons that do not overlap or have gaps between them, drawing lines that connect to each other, or placing a point exactly along an existing line |
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Term
| What is snapping tolerance? |
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Definition
| the distance within which the pointer or a feature will snap to another location. If the location being snapped to (vertex, boundary, midpoint, or connection) is within that distance, the pointer will automatically snap. |
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Term
| What is snapping priority? |
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Definition
| determines the order in which snapping will occur. Snapping occurs first in the layer at the top of the list, then in each consecutive layer down the list. |
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Term
| What is sticky move tolerance? |
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Definition
The sticky move tolerance allows you to set a minimum number of pixels your pointer must move on the screen before a selected feature is moved. This can be a useful way to prevent features from being accidentally moved small distances when they are clicked with the Edit tool.
Found in the general tab of the options menu in the Editor toolbar |
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Term
| What information can be gathered by using visual analysis? |
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Definition
Distribution
Where is ______
Where is ______ not
Patterns
Clustered
Uniform
Random
-data on map can show patterns and trends
-crime, weather, populations (density)
-Mapping change like vegetation loss
-Finding things nearby (closest), routes, travel time, development |
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Term
| How do symbols help visual analysis? |
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Definition
- Symbols along with a legend can create a visual representation of data that you're working with
-to easily see what the map represents and explore the data that you're working with
Categories
Color
Size |
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Term
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Definition
Map generalization is “decreasing the level of
detail on a map so that it remains uncluttered
when its scale is reduced.”
“… process of reducing the information content of
maps because of scale change, map purpose,
intended audience, and/or technical contraints” |
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Term
| What are the six steps of the Conceptual Model for Analysis? |
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Definition
1) State problem- What is goal? (best site for new school)
2) Break down the problem- objectives to reach goal? interactions neccessary for model? what datasets are needed? (Best site- near rec center, away from existing schools, flat land, etc.)
3) Explore input datasets- what is contained in your datasets, what relationships can be identified?
4) Perform Analysis- indentify tools needed, i.e. buffer
5) Verify results- check results from model in field, could you change something for a better result?
6) Implement results- Act on Results I.e. building school. |
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Term
| Why are these steps important when looking at a GIS analysis project? |
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Definition
-Makes you critical of them:
did they ask right question?
could they have used different inputs
is the data accurate to what it is trying to show? |
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Term
| What are the standard classifications? |
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Definition
Natural Breaks
Quantile
Equal Interval
Standard Deviation
Manual |
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Term
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Definition
“In ArcMap, a request that examines feature or
tabular attributes based on user-selected criteria
and displays only those features or records that
satisfy the criteria.” |
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Term
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Definition
Classes based on natural groupings of data values
Finds groupings and patterns within data
Class breaks are defined where there is a gap between clustered values
-good for mapping uneven distribution values, BAD for comparing map to other maps, and choosing number of classes if data is evenly distributed. |
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Term
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Definition
Each class has an equal number of features in it
-Sorts lows to highs and sums number of features
-divides total by # of classes
-Good for comparing areas of same size & mapping values evenly distributed
-BAD for close values, ending up in different classes and varying size of areas can skew patterns on map. |
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Term
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Definition
-Each class has equal range of values, good for info for notechnical audience, easier to interpret since ranges are same, and mapping continuous data like rain and temp.
-BAD for close values in different classes, some values have no data. |
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Term
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Definition
-Each class defined by distance from the mean
-good for: seeing which features are above and below avg, and bell curve
-BAD for: map doesnt show actual values, only how far from the mean
-Outliers can skew the mean, making most features fall in same class. |
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Term
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Definition
Know your data distribution
Chart it out (Histogram)
Unevenly distributed
Natural Breaks
Evenly distributed & emphasize difference between features
- Equal Interval or Standard Deviation
Evenly distributed & emphasize relative
difference between features
Quantile
-Be Wary of outliers and max 7-8 classes |
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Term
| What is Tobler’s First Law of Geography? |
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Definition
“Everything is related to everything else, but
near things are more related than distant
things.” |
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Term
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Definition
“The prediction of variables at unmeasured
locations based on a sampling of the same
variables at known locations.” |
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Term
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Definition
“… estimates are based at least in part on
other variables, and often on a total set of
measurements” |
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Term
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Definition
“The tendency of nearby objects to vary in
concert. High values are found near high
values, and low values found near low
values.”
-Does not imply causality but provide evidence of causality |
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Term
| What is Density? and why density? |
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Definition
quantity per unit area, i.e. pop/sq mile
-why? concentration of features, shows patterns, mapping areas of different sizes.
2 Ways-
I. Defined area- dot density, calculate density by area
II. Density surface\
-doesnt pinpoint exact centers, but less data processing (area density) |
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Term
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Definition
| an interconnected set of points and lines that represent possible routes form one location to another |
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Term
| What is needed to create network? |
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Definition
-Topologically correct line features
-Proper fields: lenth, time(speedlimi), restrictions |
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Term
| what type of analysis is done by networks? |
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Definition
Routing
Drive-time analysis
Point-to-point routing
Fleet routing
Service area definition
Shortest path analysis
Optimum route analysis
Closest facility analysis
Origin-destination analysis |
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Term
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Definition
| Geocoding is the process of transforming a description of a location—such as a pair of coordinates, an address, or a name of a place—to a location on the earth's surface |
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Term
| What is necessary for address matching? |
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Definition
-address locator
-GIS Address (Street centerlines w/ address ranges) or Point address layer (more accurate)
-List of address |
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