2014 Contour Data


Ayres Associates utilized these DTM components to generate the contours using the following procedures: Ayres methodology incorporates bare earth model keypoints and the hydro breaklines to create the contours. Model keypoints are a subset of bare earth points that are extracted from the full resolution point cloud using an intelligent data decimation algorithm. This algorithm works by thinning out the data in areas of little relief while keeping more points near breaks and in areas of greater variation in terrain. This process results in more manageable file sizes for TIN generation and a more cartographic appearance to the contour dataset.

All contours products were produced using Terrasolid’s TerraModeler software. TerraModeler is a full-featured terrain modeling application that incorporates intelligent filtering and smoothing algorithms for contour generation. The contours were generated from a TIN model created using the model keypoints and breaklines. Ayres employed this software’s recommended parameters and model keypoints with 20-ft spacing to create a more cartographically smoothed contour data. Additionally, Ayres filtered out enclosed contour polygons on hills and depressions that are 100-ft in circumference or less as a means of reducing file size and improving cartographic readability of the contours.


Data Format SIZE Download
2-ft Contour (Shapefile) 1.7 GB link
2-ft Contour (File Geodatabase)      938 MB      link
2-ft Contour (DGN) 1.8 GB link


2007 Contour Data

Continuous 2-ft contours were generated for Will County Illinois according to FEMA specifications using LiDAR data.


Data(Format) Size Download
2007 2-ft Contour (Shapefile) 1.0 GB link
2007 2-ft Contour (File Geodatabase)      1.5 GB link
2007 Elevation Point (Shapefile) 10.1 MB      link