## Projects

Constructing DEM — LIDAR elevation data is typically distributed as a collection of *(x,y,z)* points, but most GIS algorithms are designed for either grid or triangulated irregular network (TIN) digital elevation models. We developed two methods for efficiently converting LIDAR point sets to more conventional formats:

- Grid Construction — Our grid DEM construction algorithm uses a
quad-tree segmentation and interpolation methods to generate large scale grids from LIDAR point sets.
- TIN Construction — We construct TINs from LIDAR using a Delauny
triangulation algorithm that is efficient for large data sets. Our algorithm can also compute a constrained Delauny triangulation that
preserves linear defined by a given set hard or soft breaklines.

Noise Removal — Even with high-resolution LIDAR data, there is
some level of noise in DEMs derived from LIDAR. We are interested in methods of correcting noisy DEMs, particularly noise that impedes water flow along hydrological features. We present a method of computing a persistence score for topological features and use this persistence score to remove small topological features likely the result of noise while preserving larger features.

Terrain Flow Modeling — We are developing methods for modeling water flow over large scale terrains and making improvements to existing work in this area done as part of the TerraFlow project

Hierarchical Watershed Decomposition — This project partitions a terrain
into a hierarchy of nested watersheds using completely automated
methods. Each node in the terrain is assigned a unique watershed label,
that not only encodes its location in the watershed hierarchy but also
allows users to determine upstream and downstream watersheds using only
waterhsed labels.

Topographic Change — Because LIDAR can efficiently map large areas
quickly, it is possible to acquire regular time series datasets of
changing area. Detecting topographic change can quickly identify beach
dunes damaged by hurricanes, monitor urban development or measure change
in forest growth.