GIS Final Exam

What is modeling?

"A representation of reality used to simulate a process, understand a situation, predict an outcome, or analyze a problem. A model is structured as a set of rules and procedures, including spatial modeling tools available in a geographic information system (GIS)

What is an aspect? What does aspect of 90 mean?

Aspect is measured clockwise in degrees from 0 (due north) to 360 (again, due north coming full circle). The value of each cell in an aspect dataset indicates the direction the cell's slope faces. Flat areas have no downslope and are given a value of -1. An aspect of 90 would mean the slope faces east.

When to use intersect

Combines geometry and attribute of two inputs where they overlap

When to use buffer

Creates a ring around the feature using specified distance. Multiple buffers can be created. Buffer distance can be set to use the feature's attribute Buffer can be set to outside, inside, or outside and inside of a polygon Dissolve option merges overlapping buffer areas

When to use erase

Deletes input features that overlaps the erase feature. Is the opposite of clip

What is DEM? What additional data can you create using the DEM?

Digital Elevation Model (DEM) is a raster data that stores elevation information as the grid (cell) value. GIS programs then use this information to create and display topographic features.

When to use union

Discovers overlap between features from all feature classes and combines all geometry and attributes of two inputs

What is GPS?

Global Positioning System: a satellite-based radionavigation system developed and operated by the U.S. Department of Defense (DOD) to locate a position on earth.

What is the difference between joins and relates regarding tables?

Join: Appends the attributes from one onto the other based on a common field. Join is usually used when table relationship is one to one or many to one. Relate: Links two table: doesn't append the attributes of one to the other. Relate is usually used when there is one to many or many to many

What is trilateration?

Locating a position using distances from 3 or more known locations

When to use clip

Only keeps input features that overlaps the clip features

Define percent slope and degree slope

Percent - rise/run Degrees - angular measurement

When to use select

Selects feature based on attribute values or their spatial location. Selected features can be saved as different shapefiles

How is a distance from the satellite to GPS unit calculated?

Using the equation: Distance (d)= Velocity (v) x Time difference (∆t)

What are the six steps of modeling project work process?

buffer, intersect, erase, union, select, clip