GIS Exam #2

Click Click, goes the crab : Remote Sensing with their eyes : Oh no, pufferfish

What is remote sensing?

Collecting information about Earth’s surface without direct contact using sensors.

What role does the electromagnetic spectrum play in remote sensing?

Sensors measure reflected or emitted electromagnetic energy at different wavelengths.

What is an image band?

A specific range of wavelengths captured by a sensor.

Difference between active and passive sensors?

Passive records natural energy; active emits its own signal and records the return.

Example of a passive remote sensing system

Landsat satellite imagery.

Example of an active remote sensing system

Radar or LiDAR.

Key difference between aerial photography and satellite imagery

Aerial photos have higher spatial resolution; satellites cover larger areas repeatedly.

Common uses of imagery in GIS

Base maps, land cover classification, change detection.

What is GPS?

A satellite-based system used to determine precise location on Earth.

What information does GPS provide?

Location, elevation, time, and sometimes speed.

How does GPS determine location?

Trilateration using distances from at least four satellites.

What are the three GPS segments?

Space, Control, and User segments.

What causes GPS error?

Atmospheric delay, satellite geometry, multipath error, clock issues.

What are the two components of vector data?

Geometry and attributes.

What do rows represent in an attribute table?

Individual features.

What do columns represent in an attribute table?

Attributes describing features.

What is an attribute query?

Selecting features based on attribute values.

Common attribute query operators

=, >, <, AND, OR, LIKE.

What is a table join?

Joining tables using a common field.

What is a spatial join?

Joining data based on spatial relationships.

What is spatial selection?

Selecting features based on location.

What is spatial analysis?

Using GIS tools to answer spatial questions.

What is proximity analysis?

Measuring distance between features (e.g. buffers).

What is overlay analysis?

Combining multiple vector layers to create new information.

Intersect overlay result

Keeps only overlapping areas.

Union overlay result

Combines all areas from all layers.

Clip overlay result

Cuts features to a boundary.

Erase overlay result

Removes areas where layers overlap.

Identity overlay result

Keeps input geometry but adds overlay attributes.

What does Dissolve do?

Merges features based on a shared attribute.

What is site suitability analysis?

Identifying the best location using multiple criteria.

Nominal data definition

Categories with no order.

Ordinal data definition

Ranked categories.

Interval data definition

Equal intervals, no true zero.

Ratio data definition

Equal intervals with a true zero.

Best data types for choropleth maps

Interval and ratio data.

Why must choropleth maps use normalized data?

To avoid misleading size-based comparisons.

What is the raster data model?

Data represented as a grid of cells with values.

What is raster analysis?

Cell-by-cell analysis of raster layers.

Why convert vector data to raster?

To use raster operations and map algebra.

What is map algebra?

Mathematical operations applied to raster layers.

What does slope represent?

Steepness of terrain.

What does aspect represent?

Direction a slope faces.

What are contour lines?

Lines connecting points of equal elevation.

What is hillshade used for?

Visualizing terrain relief.

What is a viewshed?

Areas visible from a specific point.

How is census data typically stored in GIS?

As attribute data tied to polygons.

Why must census data be normalized?

To allow fair comparison between areas.

Key risk when using census data

Misinterpretation due to scale or poor joins.

Key mindset for the practical GIS exam

Think layers, criteria, analysis order, and justification.