20160426084747001.0FGDC CSDGM MetadataFALSELocal Area Network10.001201604260856560020160426143300001500000005000FGDCMicrosoft Windows 7 Version 6.1 (Build 7601) Service Pack 1; Esri ArcGIS 10.3.1.4959Iron_County_DEM2015-04-15T00:00:00Ayres Associates5201 E. Terrace Drive, Suite 200MadisonWisconsin53718US(608) 443-1200(608) 299-21841099.5728731468.126816Ayres Associates provided Iron County, Wisconsin, with lidar based topographic mapping services in the spring of 2015 as part of WROC. The LiDAR data was collected on 20150415 to 20150417 using an Optech Orion H300 sensor mounted in a fixed-wing aircraft. LiDAR data was collected to support the generation of 2-foot contours to meet FEMA vertical accuracy standards. The LiDAR data was delivered according to a 5,000 foot x 5,000 foot tile schematic. The LiDAR data was calibrated using information collected at the time of flight from GPS base stations on the ground and airborne GPS/IMU in the aircraft. The calibrated LiDAR data was processed to produce a classified point cloud, bare earth DTM, DEM, DSM, contours, breaklines, and intensity images.Wisconsinbase mapscoverIronCountyLiDAR was acquired to produce an accurate bare earth surface and to generate 2-ft contours to support county land information efforts.Any and all accessibility to data of or pertaining to the 2015 lidar dataset is to be determined by Iron County.WisconsinIronCountyTom BergmanIron CountyPlanning & Zoning Administrator300 Taconite St, Suite 115HurleyWisconsin54534zoningadmin@ironcountywi.org715-561-5414715-561-2928DEMGRIDsurface modelsurface dataterrain databare earthraster data3.125-foot pixeldatasetSimpleFALSE6TRUETRUE20160426Iron_County_DEMAny and all accessibility to data of or pertaining to the 2015 lidar dataset is to be determined by Iron County.Spatial consistency of coverage of the 2015 Iron County lidar project area was maintained throughout the dataset.A comparison of the ground survey versus lidar model values indicates a vertical root mean square error (RMSEz) of 0.319 US Survey Feet. This is within the FEMA specified vertical accuracy tolerance of 0.61 feet.
RMSEz - Urban: 0.226 US Survey Feet
RMSEz - Low Grass: 0.219 US Survey Feet
RMSEz - Tall Grass: 0.240 US Survey Feet
RMSEz - Low Trees: 0.301 US Survey Feet
RMSEz - Tall Trees: 0.257 US Survey FeetSurveys were conducted at various sites utilizing the base stations
established in the static network. These surveys established “ground truth” data at each site on different surface
types, including low grass, high grass, low trees, high trees and urban areas. Statistical comparisons were made
between ground truth points collected from the ground survey and the elevation at the associated horizontal
coordinates represented on the lidar-derived digital terrain model.
To qualify as an acceptable accuracy test, the lidar data must be compared with a dataset of higher accuracy – in
this instance, ground survey. To develop a comparable dataset of points from the lidar dataset, a utility from
proprietary software was used.
The ground control survey results were imported into an ESRI PointZ shapefile with each point’s information as
attributes. The utility then accessed the lidar and generated a triangulated irregular network (TIN), which is a
continuous digital terrain surface, using the bare-earth lidar points and the compiled breaklines. The utility probed
the TIN surface to determine its elevations at each of the survey point’s horizontal locations.
The elevation was then appended as a field to the PointZ shapefile; the attributes for each point were exported to
a database and then statistical analysis was performed.LiDAR processing utilizes several software packages, including GeoCue and the TerraSolid suite of processing components. The GeoCue software is a database management system for housing the LiDAR dataset (usually multiple gigabytes in size). GeoCue incorporates a thorough checklist of processing steps and quality assurance/quality control (QA/QC) procedures that assist in the LiDAR workflow. The TerraSolid software suite is used to automate the initial classification of the LiDAR point cloud based on a set of predetermined parameters. Lidar technicians refer to ground cover research (natural and cultural features) within the project area and determine algorithms most suitable for the initial automated LiDAR classification. (Some algorithms/filters recognize the ground in forests well, while others have greater capability in urban areas). During this process each point is given an initial classification (e.g., as ground, vegetation, or noise) based on the point's coordinates and the relation to its neighbors. Classifications to be assigned include all those outlined by ASPRS standards. The initial classifications produce a coarse and inexact dataset, but offer an adequate starting point for the subsequent manual classification procedure. During this step, "overlap" points are automatically classified (those originating from neighboring flightlines) using information gathered from the ABGPS and IMU data. Any duplicate points existing from adjacent flightlines are removed during this process. Hydrographic breaklines are collected using LiDARgrammetry to ensure hydroflattened water surfaces. This process involves manipulating the LiDAR data's intensity information to create a metrically sound stereo environment. From this generated "imagery", breaklines are photogrammetrically compiled. Breakline polygons are created to represent open water bodies. The LiDAR points that fall within these areas are classified as "water." Breaklines representing streams and rivers shall be smooth, continuous, and monotonic, and represent the water surface without any stair steps except for dams and rapids. All hydrographic breaklines include a 1.5 foot buffer, with the points being re-classified as Class 10 (ignored ground). TerraSolid is further used for the subsequent manual classification of the LiDAR points allowing technicians to view the point cloud in a number of ways to ensure accuracy and consistency of points and uniformity of point coverage.
The TIN was processed to create a GRID or digital elevation model (DEM) with 3.125-foot pixels.Ayres Associates5201 E. Terrace Drive, Suite 200MadisonWisconsin53718US(608) 443-1200(608) 299-2184Ayres Associates