Raster & Surface Analysis
Which raster data model represents the Earth’s surface elevation?
Digital Elevation Model (DEM)
Which GIS operation creates zones at a specified distance around features and can be used to define conditions like floodplains?
Buffer
Which GIS tool is used to generate a visual workflow of steps, tools and processes used in sequence?
ModelBuilder
Describe the terms of a data relationship when a simple join occurs. Give three main factors.
A simple join is a temporary data relationship.
Cardinality = one to one or many to one
Common fields between tables must be the same data type
Which operational tool (found when right-clicking on an attribute in a table) is used to determine the mean, mode, sum, & standard deviation of a given attribute?
Summary Statistics
Which raster operation/tool calculates the steepness or rate of change in elevation.
Slope
Which overlay tool combines multiple layers and retains only shared areas?
HINT: This can be used for both vector and raster data!
Intersect
What programming language is commonly used to write GIS-based data analysis scripts?
Python
How do the two main (vector) data query tools differ?
Select by Attributes: Generates a subset of data based on shared characteristics of a single attribute.
Select by Location: generates a subset based on proximity or other map placement characteristics.
What must be consistent in order for field calculations to incorporate data from other attributes?
Data types must be consistent
(numeric: Double, integer, etc.)
Which raster analysis tool identifies all areas visible from a specific observation point?
Viewshed
What type of rasters tend to be optimal for multi-criteria analysis, such as a suitability index?
Boolean rasters
You want to share a dataset that includes all data and dependencies in a single downloadable file for desktop use. What do you do?
Export/Share Package
AND, OR and XOR are commutative Boolean operations.
What does that mean?
Values are transversal: A AND B is equal to B AND A.
Order of operations does not matter for values A and B.
Operations applied right-to-left can also be applied left-to-right.
Explain the difference between a gis layer and a shapefile.
Layer File: Stores spatial data and display properties, but no data for analysis.
Shapefile: A spatial data model used by GIS software (minus display properties), but contains data which can be analyzed.
Name three advantages or disadvantages of raster data sets and their use.
Raster Advantages
•Good for complex analysis (e.g. map algebra)
•Efficient for overlays
•Data structure common for imagery
Raster Disadvantages
•Large datasets
•No topology
•Maps less "realistic“ (blocky vs resembling reality)
For a weighted overlay raster analysis, what is ONE example of how to interpret results?
1. Negative values = low, Positive values = high
2. Defined 0 value as a midrange
3. Typically 1, 5 or other numerical values for a defined range
Which GIS tool leads the user through the steps to define a study area, creating feature classes, digitizing boundaries, and clipping data to the boundary?
Task Designer
Explain the difference between simple, summarized & spatial joins
Simple Join: one to one/many to one
Summarized: Overcomes rule of joining violations, totals values of one to many/many to many; relies on statistics (sum, mean, median, variance, etc.)
Spatial: Considers proximity/containment
What is SQL and how is it used in GIS?
HINT: What do the letters represent?
Structured Query Language (SQL):
An established syntax for creating logical expressions to extract records from a database according to specified criteria.
What name is given to raster data where x, y, and z coordinates are defined?
Voxcells
What value must all weights assigned to a multicritera raster analysis add up to?
All weights assigned need to add up to 1 or 1.00, distributed across all layers included in the analysis.
The weight assumes the proportion of influence, value or priority given to the layer in question.
What colors and shapes are used within ModelBuilder and what do each represent?
1. Inputs (blue ovals)
2. Tools (yellow squares)
3. Outputs (green ovals)
Which dataset (2 possible options) enables Boolean algebraic calculations to create an index value based on multiple datasets?
Raster datasets
To concatenate data means to join or combine data elements end-to-end to form a single, continuous result.
In a GIS attribute table, you create a new field by combining values from multiple fields—such as merging city and state into a single label (e.g., “Cedar Falls, IA”) and include a character as a separator, such as a comma to denote a list.