Eddie Tsz-Yam Lau

2013

W. Randolph Franklin, You Li, Tsz-Yam Lau, and Peter Fox. CUDA-accelerated HD-ODETLAP: lossy high dimensional gridded data compression. In Xuan Shi, Volodymyr Kindratenko, and Chaowei Yang, editors, Modern Accelerator Technologies for Geographic Information Science. Springer, 2013.
[abstract▼] [details] [full text] [BibTeX▼]

We present High-dimensional Overdetermined Laplacian Partial Differential Equations (HD-ODETLAP), an algorithm and implementation for lossy compression of high-dimensional arrays of data. HD-ODETLAP exploits autocorrelations in the data in any dimension. It also adapts to regions in the data with varying value ranges, resulting in the maximum error being closer to the RMS error. HD-ODETLAP compresses a data array by iteratively selecting a representative set of points from the array. That set of points, efficiently coded, is the compressed dataset. The compressed dataset is uncompressed by solving an overdetermined sparse system of linear equations for an approximation to the original array. HD-ODETLAP uses NVIDIA CUDA called from MATLAB to exploit GPU parallel processing to achieve considerable speedup compared to execution on a CPU. In addition, HD-ODETLAP compresses much better than JPEG2000 and 3D-SPIHT, when fixing either the average or the maximum error. An application is to facilitate storage and transmission of voluminous datasets for better climatological and environmental analysis and prediction.
```
@incollection{hdodetlap-2013,
    author = "Franklin, W. Randolph and Li, You and Lau, Tsz-Yam and Fox, Peter",
    editor = "Shi, Xuan and Kindratenko, Volodymyr and Yang, Chaowei",
    title = "{CUDA}-accelerated {HD-ODETLAP}: Lossy high dimensional gridded data compression",
    booktitle = "Modern Accelerator Technologies for Geographic Information Science",
    year = "2013",
    isbn = "978-1-4614-8744-9",
    publisher = "Springer",
    href = "\bibhref{165-2013-hdodetlap}",
    mykey = "youli lau odetlap parallel"
}
```
Tsz-Yam Lau and W. Randolph Franklin. River network completion without height samples using geometry-based induced terrain. Cartography and Geographic Information Science, 40(2):316–325, 29 Apr 2013. arXiv:http://www.tandfonline.com/doi/pdf/10.1080/15230406.2013.780785, doi:https://doi.org/10.1080/15230406.2013.780785.
[abstract▼] [details] [full text] [BibTeX▼]

We present an improved method for connecting broken river segments by incorporating segment geometry into the induced terrain approach. The reconnection problem is important in aerial photography. Canopies and clouds cover parts of rivers, and a complete river network is necessary for transportation, land-use planning, and floodplain control. Our previously presented induced terrain approach guarantees that the global network topology is hydrologically consistent. However, it assumes many reliable height samples, which may be unavailable because of extensive view obstacles or gentle surfaces, to reconstruct the induced terrain surface. In this paper, we exploit river segment geometries to generate the induced terrain. We assign lowest heights to the known river locations, and higher and higher heights for locations further and further away. Since areas radiating from segment tips tend to be where a river is broken, we assign relatively small heights to these areas, so as to favor water flow toward them in the subsequent river derivation. On average, such a tip-biased model improves reconnection accuracy by five percentage points (which is 40\% of what we would have been corrected if we had had rich height samples covering 10\% of the terrain cells) over the intuitive baseline model in which the height of a location increases with its distance from the respective nearest river location, without considering the potential effect of segment tips as the tip-biased approach.
```
@article{lau-cagis-2013,
    author = "Lau, Tsz-Yam and Franklin, W. Randolph",
    title = "River network completion without height samples using geometry-based induced terrain",
    journal = "Cartography and Geographic Information Science",
    volume = "40",
    number = "2",
    pages = "316-325",
    year = "2013",
    month = "29 Apr",
    doi = "https://doi.org/10.1080/15230406.2013.780785",
    eprint = "http://www.tandfonline.com/doi/pdf/10.1080/15230406.2013.780785",
    href = "\bibhref{164-cagis2013-better-completion}",
    mykey = "hydro lau"
}
```

2012

Tsz-Yam Lau and W. Randolph Franklin. Automated artifact-free seafloor surface reconstruction with two-step ODETLAP (Ph.D. showcase). In 20th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems (ACM SIGSPATIAL GIS 2012). Redondo Beach, CA, 6–9 Nov 2012.
[details] [full text] [poster] [BibTeX▼]

@inproceedings{lau-acmgis-2012,
    author = "Lau, Tsz-Yam and Franklin, W. Randolph",
    title = "Automated artifact-free seafloor surface reconstruction with two-step {ODETLAP} ({Ph.D.} Showcase)",
    booktitle = "20th {ACM} {SIGSPATIAL} International Conference on Advances in Geographic Information Systems ({ACM SIGSPATIAL GIS} 2012)",
    year = "2012",
    address = "Redondo Beach, CA",
    month = "6--9 Nov",
    mykey = "lau odetlap",
    customlinkposter = "https://wrfranklin.org/p/160-acmgis2012-seafloor-poster.pdf",
    href = "\bibhrefpp{160-acmgis2012-seafloor}{160-acmgis2012-seafloor-poster.pdf}"
}

W. Randolph Franklin, You Li, Tsz-Yam Lau, and Peter Fox. CUDA-accelerated HD-ODETLAP: lossy high dimensional gridded data compression. In 2012 International Workshop on Modern Accelerator Technologies for GIScience (MAT4GIScience 2012). Columbus OH, 18 Sep 2012.
[details] [full text] [slides] [BibTeX▼]

@inproceedings{giscience-hdodetlap-2012,
    author = "Franklin, W. Randolph and Li, You and Lau, Tsz-Yam and Fox, Peter",
    title = "{CUDA}-accelerated {HD-ODETLAP}: Lossy high dimensional gridded data compression",
    booktitle = "2012 International Workshop on Modern Accelerator Technologies for {GIScience} ({MAT4GIScience} 2012)",
    year = "2012",
    address = "Columbus OH",
    month = "18 Sep",
    mykey = "youli lau odetlap",
    customlinkslides = "https://wrfranklin.org/p/156-mat4giscience2012-hdodetlap-talk.pdf",
    href = "\bibhrefpt{156-mat4giscience2012-hdodetlap}{156-mat4giscience2012-hdodetlap-talk.pdf}"
}

Tsz-Yam Lau and W. Randolph Franklin. Improving river network completion under absence of height samples using geometry-based induced terrain approach. In 2012 AutoCarto International Symposium on Automated Cartography. Columbus OH, 16–18 Sep 2012.
[details] [full text] [slides] [BibTeX▼]

@inproceedings{lau-autocarto-2012,
    author = "Lau, Tsz-Yam and Franklin, W. Randolph",
    title = "Improving river network completion under absence of height samples using geometry-based induced terrain approach",
    booktitle = "2012 AutoCarto International Symposium on Automated Cartography",
    year = "2012",
    address = "Columbus OH",
    month = "16--18 Sep",
    customlinkslides = "https://wrfranklin.org/p/154-autocarto2012-better-completion-talk.pptx",
    href = "\bibhrefpt{154-autocarto2012-better-completion}{154-autocarto2012-better-completion-talk.pptx}",
    mykey = "lau hydro"
}

Tsz-Yam Lau and W. Randolph Franklin. Better completion of fragmentary river networks with the induced terrain approach by using known non-river locations. In 15th International Symposium on Spatial Data Handling. Bonn, Germany, 22–24 Aug 2012.
[details] [full text] [slides] [BibTeX▼]

@inproceedings{lau-sdh-2012,
    author = "Lau, Tsz-Yam and Franklin, W. Randolph",
    title = "Better completion of fragmentary river networks with the induced terrain approach by using known non-river locations",
    booktitle = "15th International Symposium on Spatial Data Handling",
    year = "2012",
    address = "Bonn, Germany",
    month = "22--24 Aug",
    customlinkslides = "https://wrfranklin.org/p/157-sdh2012-completion-talk.ppt",
    mykey = "lau hydro",
    href = "\bibhrefpt{157-sdh2012-completion}{157-sdh2012-completion-talk.ppt}"
}

Tsz-Yam Lau. Two-step ODETLAP and induced terrain for improved geographical data reconstruction. PhD thesis, Rensselaer Polytechnic Institute, 2012.
[details] [full text] [BibTeX▼]

@phdthesis{lau-phd,
    author = "Lau, Tsz-Yam",
    title = "Two-step {ODETLAP} and induced terrain for improved geographical data reconstruction",
    school = "Rensselaer Polytechnic Institute",
    mykey = "odetlap hydro lau theses bathy",
    year = "2012"
}

2011

Tsz-Yam Lau, You Li, and W. Randolph Franklin. Joining fragmentary river segments with elevations and water flow directions using induced terrain (extended abstract). In 21st Fall Workshop on Computational Geometry. City College, New York City, USA, 4–5 Nov 2011.
[details] [full text] [BibTeX▼]

@inproceedings{lau-fwcg-2011,
    author = "Lau, Tsz-Yam and Li, You and Franklin, W. Randolph",
    title = "Joining fragmentary river segments with elevations and water flow directions using induced terrain (extended abstract)",
    booktitle = "21st Fall Workshop on Computational Geometry",
    year = "2011",
    month = "4--5 Nov",
    address = "City College, New York City, USA",
    mykey = "youli lau hydro",
    href = "\bibhref{150-fwcg2011-lau}"
}

Tsz-Yam Lau and W. Randolph Franklin. Completing fragmentary river networks via induced terrain. Cartography and Geographic Information Science, 38(2):162–174, April 2011. URL: https://www.tandfonline.com/doi/abs/10.1559/15230406382161a, doi:https://doi.org/10.1559/15230406382161a.
[abstract▼] [details] [full text] [BibTeX▼]

Fragmentary river segments have to be reconnected before addressing various routing and tracking problems. Elevation determines drainage directions, so the partial heights available through LiDAR may provide useful hints on how the segments should be joined. However, it is not trivial how this information can be applied. This paper bridges this gap by proposing the induced structure approach, which first approximates a terrain compatible with those observations, and then derives a river network from that induced terrain. Since the network is derived from an induced terrain that honors the partial observations, we expect that the derived river network will enforce most restrictions imposed by the partial observations. This paper also provides specifics on the implementation. In the first step regarding terrain reconstruction, we find that the optimal scheme depends on the height sample distribution. If the samples are sparsely yet evenly distributed, natural neighbor interpolation with stream burning (NN-SB) is the most cost-effective. If the samples are offered only at the given river locations, the hydrology-aware version of Over determined Palladian Partial Differential Equation (HA-ODETLAP) should be used instead. In the second step concerning river derivation, we find it necessary to favor those given river locations. Otherwise they will be missed out. We set their respective initial water amounts to the critical accumulation level to ensure a river flows across them. In the subsequent branch thinning process, those locations are protected from being trimmed. We foresee applications of our solution framework in a few 2D and 3D network tracing problems with similar observation distribution, like dendrite network reconstruction.
```
@article{lau-cagis-2011,
    author = "Lau, Tsz-Yam and Franklin, W. Randolph",
    title = "Completing fragmentary river networks via induced terrain",
    journal = "Cartography and Geographic Information Science",
    year = "2011",
    month = "April",
    pages = "162-174",
    volume = "38",
    number = "2",
    doi = "https://doi.org/10.1559/15230406382161a",
    url = "https://www.tandfonline.com/doi/abs/10.1559/15230406382161a",
    mykey = "lau hydro",
    href = "\bibhref{147-cagis-hydro-lau}"
}
```

2010

Tsz-Yam Lau and W. Randolph Franklin. Completing river networks with only partial river observations via hydrology-aware ODETLAP. In 20th Annual Fall Workshop on Computational Geometry (FWCG 2010). Stony Brook University, Stony Brook, NY 11794, USA, 29–30 Oct 2010. (extended abstract and talk).
[details] [full text] [slides] [BibTeX▼]

@inproceedings{lau-fwcg-2010,
    author = "Lau, Tsz-Yam and Franklin, W. Randolph",
    title = "Completing River Networks with Only Partial River Observations via Hydrology-Aware {ODETLAP}",
    booktitle = "20th Annual Fall Workshop on Computational Geometry ({FWCG} 2010)",
    month = "29--30 Oct",
    year = "2010",
    note = "(extended abstract and talk)",
    mykey = "lau hydro odetlap",
    address = "Stony Brook University, Stony Brook, NY 11794, USA",
    customlinkslides = "https://wrfranklin.org/p/138-fwcg2010-lau-talk.pdf",
    href = "\bibhrefat{138-fwcg2010-lau}{138-fwcg2010-lau-talk.pdf}"
}

W. Randolph Franklin, Zhongyi Xie, Eddie Lau, and You Li. Algorithms for terrain and bathymetric sensor data. In ICA Workshop on Advances in Sensors and Algorithms for Topographic and Thematic Mapping. Orlando, Florida, 19 Nov 2010. The International Cartographic Association (ICA) Commission on Mapping from Satellite Imagery.
[details] [full text] [slides] [BibTeX▼]

@inproceedings{ica-2010,
    author = "Franklin, W. Randolph and Xie, Zhongyi and Lau, Eddie and Li, You",
    title = "Algorithms for terrain and bathymetric sensor data",
    booktitle = "{ICA} Workshop on Advances in Sensors and Algorithms for Topographic and Thematic Mapping",
    year = "2010",
    address = "Orlando, Florida",
    month = "19 Nov",
    organization = "The {International} Cartographic Association {(ICA)} Commission on Mapping from Satellite Imagery",
    customlinkslides = "https://wrfranklin.org/p/143-orlando-ica-sensors-2010-talk.pdf",
    mykey = "xie youli lau bathy",
    href = "\bibhrefpt{143-orlando-ica-sensors-2010}{143-orlando-ica-sensors-2010-talk.pdf}"
}

Tsz-Yam Lau and W. Randolph Franklin. Completing fragmentary river networks via induced terrain. In Geospatial Data and Geovisualization: Environment, Security, and Society, a special joint symposium of ISPRS Technical Commission IV & AutoCarto 2010. Orlando, Florida, 15–18 Nov 2010.
[details] [full text] [slides] [BibTeX▼]

@inproceedings{lau-autocarto-2010,
    author = "Lau, Tsz-Yam and Franklin, W. Randolph",
    title = "Completing fragmentary river networks via induced terrain",
    booktitle = "Geospatial Data and Geovisualization: Environment, Security, and Society, a special joint symposium of {ISPRS} Technical Commission {IV} \\& {AutoCarto} 2010",
    year = "2010",
    address = "Orlando, Florida",
    month = "15--18 Nov",
    mykey = "lau hydro",
    customlinkslides = "https://wrfranklin.org/p/135-autocarto2010-lau-talk.pptx",
    href = "\bibhrefpt{135-autocarto2010-lau}{135-autocarto2010-lau-talk.pptx}"
}

You Li, Tsz-Yam Lau, Chris Stuetzle, Peter Fox, and W. Randolph Franklin. 3D oceanographic data compression using 3D-ODETLAP. In 18th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems (ACM SIGSPATIAL GIS 2010). San Jose, CA, USA, 2–5 Nov 2010. (PhD Dissertation showcase).
[details] [full text] [slides] [BibTeX▼]

@inproceedings{li-acmgis-2010,
    author = "Li, You and Lau, Tsz-Yam and Stuetzle, Chris and Fox, Peter and Franklin, W. Randolph",
    title = "{3D} oceanographic data compression using {3D-ODETLAP}",
    booktitle = "18th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems (ACM SIGSPATIAL GIS 2010)",
    year = "2010",
    month = "2--5 Nov",
    mykey = "youli odetlap lau stuetzle",
    address = "San Jose, CA, USA",
    customlinkslides = "https://wrfranklin.org/p/139-acmgis2010-li-talk.pptx",
    href = "\bibhrefpt{139-acmgis2010-li}{139-acmgis2010-li-talk.pptx}",
    note = "(PhD Dissertation showcase)"
}