Video #18 (Surfaces) Flashcards
(25 cards)
What are some examples of CONTINOUS surfaces?
Elevation, air pressure, wind
What data type should always be possible in continuous surface analysis?
Interval or Ratio
What are “critical points”?
Critical points are the points of greatest and least values
How are surfaces represented?
With the use of points, lines and area
What is Vector GRID?
Sampling a surface at specific intervals (1.0kmx1.0km)
What is Vector TIN?
Sample points are often taken at ridges, peaks and other POIs
What does Vector TIN excel at representing?
Topography
What is the TIN composed of?
Nodes, lines and triangular faces
What does TIN stand for?
Triangular Irregular Network
What does TIN divide the world into?
Triangles where variation is approximated within each traingle
Where can we see a conflict between representation and visualization?
Visualization can hide some representation
How can GRID and TIN change the model for the data?
TIN can be more precise in more important areas (peaks, cliffs) than GRID can be with the same number of nodes and lines.
What advantages does TIN have over GRID?
TIN can choose where to be precise while GRID is less precise everywhere. Think of it this way:
TIN is more focused on a specific object in 1080p
GRID is less focused on a specific object in 720p
What issues arise with TIN while using interpolation?
Ridges or pixelated surfaces are not representing the land accurately if used incorrectly
What should you consider while choosing an interpolation strategy (GRID or TIN)?
What are you trying to represent? Can it be represented? How efficiently does it represent the phenomena?
What is slope operation in surface data?
Slope can be calculated by taking subtracting elevation B by elevation A to give a slope %
What is the aspect operation?
The direction the slope is facing. This is done using angles and slope %
What are some uses of slope and aspect?
Analysis of vegetation patterns, modeling erosion, direction of runoff
What is a real world example of aspect and slope usage?
If you want to find the best place to clear cut for an emergency dam relief system, knowing where the water will naturally go using slope and aspect is important
How do you find slope?
Rise/Run
Confluence maps show…
Flow
What does hill shading do?
Simulate the appearance of a surface with noon sunlight by re-rendering the raster data of a DEM
What is a DEM?
A digital elevation model
What are some modern methods of generating surface data?
LiDAR, multibeam-sonar, SfM (structure from motion) Photography
