Chapter5 Flashcards
(18 cards)
DTM generation techniques cannot capture the full complexity of a
surface.
Because have 2 problems
- A sampling problem
- A representation problem
General Ways to Represent A Surface
(1) Mathematical Function:
(2) Image of the Surface:
(1)Expresses elevation as a function of the horizontal coordinates.
(2)
• Explicitly gives the elevation at some set of point.
• No functional dependence with horizontal coordinates.
Surface Classifications
(1) Functional Surface & Solid Surface
(2) Continuous Surfaces & Discontinuous Surfaces
(3) Smooth Surfaces & Non-smooth Surfaces
Different between Functional Surfaces and Solid Surfaces
The Functional Surfaces its Store a single Z value for any given (X, Y) location and usually referred to as 2.5D surfaces.
But the Solid Surfaces its True 3D models capable of storing multiple Z values for any given (X,
Y) location.
Different between Continuous & Discontinuous Surfaces
Continuous Surfaces are functional Surfaces but Discontinuous Surfaces are solid surfaces
Defined the smoothness
change of surface normal
from one location to the other.
Different between Smooth & Non-smooth Surfaces
Smooth surfaces are continuous surfaces but Non-smooth Surfaces are discontinuous surfaces
Different between Interpolation and Extrapolation
Interpolation: Predicts within the observed area.
Extrapolation: Predicts beyond the observed area.
Give 2 examples Interpolation in DTM: When to Use?
• The data available do not cover the complete range of interest.
• Need Zi at single unsampled points.
Give 2 examples Criteria for selecting a DTM interpolation method
(1) Desired degree of accuracy.
(2) Computational effort involved
Interpolation Methods: Classification
(1) Exact & Inexact Interpolation
(2) Global & Local Interpolation
(3) Deterministic & Stochastic Interpolation
Different between Exact Interpolation Inexact Interpolation
Exact Interpolation: Estimated values match sample points.
Inexact Interpolation: Estimated values differ; residuals measure accuracy.
Different between Global & Local Interpolation
Global Interpolation:
• Uses all available sample points
Local Interpolation:
using some reference points (nearest
sample points)
Different between Deterministic & Stochastic Interpolation
Deterministic Interpolation:
not take into account the statistical
properties .
Stochastic Interpolation:
take into account the statistical properties
Global Interpolation Methods
(1) Trend Surface Analysis (TSA)
(2) Fourier (Transform/Series) Analysis
(3) Kriging
Trend Surface Analysis (TSA)
The surface is approximated by a polynomial expansion.
TSA: Advantages
1.A unique surface is generated.
2.Computation time for low-order surfaces is low
Defined the Kriging
Kriging is a geostatistical interpolation technique.
