tsz -yam lau and w. randolph franklin rensselaer polytechnic institute
DESCRIPTION
Improving river network completion under absence of height samples using geometry-based induced terrain approach. Tsz -Yam Lau and W. Randolph Franklin Rensselaer Polytechnic Institute partially supported by NSF grants CMMI-0835762 and IIS-1117277. Broader Impact. - PowerPoint PPT PresentationTRANSCRIPT
Autocarto 2012 Lau & Franklin 1
Improving river network completion under absence of height samples using geometry-
based induced terrain approach
Tsz-Yam Lau and W. Randolph Franklin
Rensselaer Polytechnic Institute
partially supported by NSF grants CMMI-0835762 and IIS-1117277
Sept 18, 2012
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Broader Impact
• Better real-time monitoring of rapidly-changing hydrography with a huge set of aerial photographs captured from time to time
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Contribution
• Enhance the induced terrain approach with river segment geometry to further improve automated river reconnection accuracy
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The induced terrain approach
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(Lau and Franklin, 2011)
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Missing partial heights: obstacles
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Missing partial heights: flat surface
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Amazon River basin-wide water-surface SRTM C-band heights (blue dots). A 3rd order polynomial fit of the data (green line) and with its slope (red line).
(LeFavor and Alsdorf , 2005)
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Baseline terrain model
• V shapes centered at given river locations
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Favoring shortest-path reconnections
• A pair of river locations distant further apart has a higher cost to be connected.
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x x x Known river locations
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Favoring shortest-path reconnections
• A pair of river locations distant further apart has a higher cost to be connected.
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x x x
Easy
Difficult
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Favoring shortest-path reconnections
• Pros: Match human heuristics of linking segments with shortest length– Shortest length, lowest cost
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outlet outlet
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Favoring shortest-path reconnections
• Pros: Match human heuristics of linking segments with shortest length– Shortest length, lowest cost
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outlet outlet
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Favoring shortest-path reconnections
• Cons: Ignore “extend from tips” heuristic
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outlet
outlet
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Favoring shortest-path reconnections
• Cons: Ignore “extend from tips” heuristic
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outlet
Reconnection with baseline model
outlet
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Favoring shortest-path reconnections
• Cons: Ignore “extend from tips” heuristic
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outlet
Expected extension directionsoutlet
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Favoring shortest-path reconnections
• Cons: Ignore “extend from tips” heuristic
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outlet
Expected reconnectionoutlet
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Favoring shortest-path reconnections
• Cons: Ignore “Join segments which faces each other” heuristic
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outlet
outlet
17
Favoring shortest-path reconnections
• Cons: Ignore “Join segments which faces each other” heuristic
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outlet
outlet
Reconnection with baseline model
18
Favoring shortest-path reconnections
• Cons: Ignore “Join segments which faces each other” heuristic
Sept 18, 2012 Autocarto 2012 Lau & Franklin
outletExpected reconnection
outlet
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Favoring shortest-path reconnections
• Cons: Ignore “replicate straightness behavior in the segment extension” heuristic
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outlet
outlet
20
Favoring shortest-path reconnections
• Cons: Ignore “replicate straightness behavior in the segment extension” heuristic
Sept 18, 2012 Autocarto 2012 Lau & Franklin
outlet
outlet
Reconnection with baseline model
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Favoring shortest-path reconnections
• Cons: Ignore “replicate straightness behavior in the segment extension” heuristic
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outlet
outlet
Expected reconnection
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Improvement
• Reduce the rate of height increase at locations radiated from segment tips
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Parameter setting:
• Determine the bending that we accept for privileged connections of mutually facing segments
• Give good results with /4 or /8 on average.
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Parameter setting: ’
• Control to what extent we favor height growing according to segment’s straightness over proximity to river locations
• Give good results with 0.5 on average.
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Results
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40% of what we can correct with rich height samples (density = 10%)
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Conclusion
• Adjust the probability of receiving reconnection of different parts of the river segments
• Shortest path is no longer the single criterion to determine how segments are reconnected
• Recover 40% of what can be achieved with rich height samples (density = 10%)
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Future work
• Port the induced terrain framework to completion of 3D dendrite networks
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Questions?
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40% of what we can correct with rich height samples (density = 10%)