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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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Autocarto 2012 Lau & Franklin 2
Broader Impact
• Better real-time monitoring of rapidly-changing hydrography with a huge set of aerial photographs captured from time to time
Sept 18, 2012
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Autocarto 2012 Lau & Franklin 3
Contribution
• Enhance the induced terrain approach with river segment geometry to further improve automated river reconnection accuracy
Sept 18, 2012
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Autocarto 2012 Lau & Franklin 4
The induced terrain approach
Sept 18, 2012
(Lau and Franklin, 2011)
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Autocarto 2012 Lau & Franklin 5
Missing partial heights: obstacles
Sept 18, 2012
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Autocarto 2012 Lau & Franklin 6
Missing partial heights: flat surface
Sept 18, 2012
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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Autocarto 2012 Lau & Franklin 7
Baseline terrain model
• V shapes centered at given river locations
Sept 18, 2012
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Autocarto 2012 Lau & Franklin 8
Favoring shortest-path reconnections
• A pair of river locations distant further apart has a higher cost to be connected.
Sept 18, 2012
x x x Known river locations
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Autocarto 2012 Lau & Franklin 9
Favoring shortest-path reconnections
• A pair of river locations distant further apart has a higher cost to be connected.
Sept 18, 2012
x x x
Easy
Difficult
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Autocarto 2012 Lau & Franklin 10
Favoring shortest-path reconnections
• Pros: Match human heuristics of linking segments with shortest length– Shortest length, lowest cost
Sept 18, 2012
outlet outlet
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Autocarto 2012 Lau & Franklin 11
Favoring shortest-path reconnections
• Pros: Match human heuristics of linking segments with shortest length– Shortest length, lowest cost
Sept 18, 2012
outlet outlet
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Autocarto 2012 Lau & Franklin 12
Favoring shortest-path reconnections
• Cons: Ignore “extend from tips” heuristic
Sept 18, 2012
outlet
outlet
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Autocarto 2012 Lau & Franklin 13
Favoring shortest-path reconnections
• Cons: Ignore “extend from tips” heuristic
Sept 18, 2012
outlet
Reconnection with baseline model
outlet
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Autocarto 2012 Lau & Franklin 14
Favoring shortest-path reconnections
• Cons: Ignore “extend from tips” heuristic
Sept 18, 2012
outlet
Expected extension directionsoutlet
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Autocarto 2012 Lau & Franklin 15
Favoring shortest-path reconnections
• Cons: Ignore “extend from tips” heuristic
Sept 18, 2012
outlet
Expected reconnectionoutlet
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Autocarto 2012 Lau & Franklin 16
Favoring shortest-path reconnections
• Cons: Ignore “Join segments which faces each other” heuristic
Sept 18, 2012
outlet
outlet
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17
Favoring shortest-path reconnections
• Cons: Ignore “Join segments which faces each other” heuristic
Sept 18, 2012 Autocarto 2012 Lau & Franklin
outlet
outlet
Reconnection with baseline model
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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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Autocarto 2012 Lau & Franklin 19
Favoring shortest-path reconnections
• Cons: Ignore “replicate straightness behavior in the segment extension” heuristic
Sept 18, 2012
outlet
outlet
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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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Autocarto 2012 Lau & Franklin 21
Favoring shortest-path reconnections
• Cons: Ignore “replicate straightness behavior in the segment extension” heuristic
Sept 18, 2012
outlet
outlet
Expected reconnection
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Improvement
• Reduce the rate of height increase at locations radiated from segment tips
Sept 18, 2012
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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.
Sept 18, 2012
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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.
Sept 18, 2012
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Results
Sept 18, 2012
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%)
Sept 18, 2012
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Future work
• Port the induced terrain framework to completion of 3D dendrite networks
Sept 18, 2012
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Questions?
Sept 18, 2012
40% of what we can correct with rich height samples (density = 10%)