Week 4 and 5

Week 4: Geodesy, Projections and Coordinate Systems

#5 Review Questions

  1.  How do you define a Raster data model?

Raster data contains pixels, cells, and grids.


  1.  What are raster properties?

Extent (#rows, # cols) , Resolutions (cell size), and location.


  1. What are the major differences between Stacks and Pyramids? 

Stacks combine multiple raster layers (most useful for color images)  while pyramids improve the performance of rasters (Allow for different levels of detail at different display scales. – Only needs to be built once)


  1.  What are the implications of cell size? 

Smaller cell sizes offer greater precision but potentially lead to larger file sizes and slower processing times, while larger cell sizes provide less accurate representation but can be faster to analyze


  1. What are the major differences between stacks of Lossy Compression and Non-Lossy Compression? 


Lossy Compression does not maintain original pixel values after compression and  Non-lossy (lossless) compression maintains original digital number pixel values.


  1. What are the differences between Raster vs Vector data?



  1. When do you use Vector data? 

Vector data is preferable for topological and network analyses, 

  1. When do you use Raster data? 

Raster data is better for spatial analyses that cover extensive areas.


  1.  What are some problems with data conversion? From Raster to Vector (Vice - versa) 

Very small features (ponds, small canopy openings, rare vegetation types) can be lost entirely if they are smaller than the cell size.



Week 5: Data Input Source & Transformation (Georeferencing)

Review Questions #6

  1. How do we define a Datum? 

Datum is a reference surface, or model of Earth that is used for plotting locations anywhere on the actual surface of Earth. The Datum represents the size and shape of the earth

  1. What is Geodesy? 

The science measuring Earth’s shape to develop these kinds of models

(geoid and ellipsoid) and reference surfaces referred to as geodesy


  1. What are three major different types of coordinate systems? 

Cartesian (rectangular), cylindrical, and spherical


  1. What are the difference between a geographic coordinate system (GCS) and a projected coordinate system (PCS)?

A GCS defines where the data is located on the earth’s surface while a A PCS tells the data how to draw on a flat surface, like on a paper map or a computer screen.


  1.  What a “developable“ surface? 

A “developable“ surface is a surface that can be flattened to a plane without introducing distortion from compression or stretching. 


  1. Define projection. 

A projection is the visual representation of those spatial measurements on a different surface.

  1. What is UTM?

Universal Transverse Mercator coordinate system


  1.  What are the three types of “developable” surface? 

Planes, cones, and cylinders. 



  1. True or False: The geoid is a hypothetical Earth surface that represents the mean sea level in the absence of winds, currents, and most tides. 


  1. Fill in the blanks: Representing the earth’s surface in two dimensions causes distortion in ____shape_____, area___, ____distance______, or direction. 


  1. Define Vertices and Label: 

Vertices define line shape


  1. Define Nodes and Label: 

Nodes are at the endpoint of the line


  1. List Common errors in editing 

Errors include undershooting, overshoot, dangling nodes, pseudonode, polygon label point, missing label point, line crossing- no node


  1. Define Line Snapping: 

When a vertex or node is “close” to a line or endpoint, the lines are “snapped” together


  1. .What is COGO? 

COGO is coordinate geomet