Going ‘On the Grid’: The Impacts of Point-to-Pixel Conversion Methods on Uncertainty in Spatial Data
Thursday, August 13, 2015: 11:30 AM-1:15 PM
311, Baltimore Convention Center
Leah A. Wasser
Claire K. Lunch
As ecologists we often need to create seamless maps, in raster or gridded format, of biomass, carbon, vegetation height or other metrics from points sampled on the landscape. However, when converting points to pixels, there are many processing choices that can impact the uncertainty of derived products. Incomplete understanding of the uncertainty in derived products, in turn, impacts downstream analytical and model results and can lead to erroneous conclusions drawn from the data. This lunchtime power workshop will demonstrate, on the fly, the impacts of selecting various methods of interpolation for converting points to pixels (e.g. Kriging, IDW, TIN), as well as non-interpolated mathematical methods. We will use a height normalized LiDAR point cloud, which represents canopy height values, to create several raster grids of canopy height (known as a canopy height model), using different point-to-pixel conversion methods. We will then quantify and assess differences in height values derived using these different methods.
Katherine M. Thibault
Participants will leave the workshop with a better understanding of various point-to-pixel conversion methods (interpolators and other gridding methods), how to interpret the resulting pixel values, how to perform basic raster math, and some of the key questions we should ask ourselves before creating a seamless grid from a point-based dataset. We will highlight the fundamentals of gridding using open source tools such as QGIS, python and R.