2015 NRCS Lidar: Christian County, IL

Create custom data files by choosing data area, product type, map projection, file format, datum, etc. A new metadata will be produced to reflect your request using this record as a base. Change to an orthometric vertical datum is one of the many options.

Bulk download of data files in LAZ format, geographic coordinates, orthometric heights. Note that the vertical datum (hence elevations) of the files here are different than described in this document. They will be in an orthometric datum.

The Data Access Viewer (DAV) allows a user to search for and download elevation, imagery, and land cover data for the coastal U.S. and its territories. The data, hosted by the NOAA Office for Coastal Management, can be customized and requested for free download through a checkout interface. An email provides a link to the customized data, while the original data set is available through a link within the viewer.

Link to the reports, breaklines, metadata, and spatial metadata.

Entwine Point Tile (EPT) is a simple and flexible octree-based storage format for point cloud data. The data is organized in such a way that the data can be reasonably streamed over the internet, pulling only the points you need. EPT files can be queried to return a subset of the points that give you a representation of the area. As you zoom further in, you are requesting higher and higher densities. A dataset in EPT will contain a lot of files, however, the ept.json file describes all the rest. The EPT file can be used in Potree and QGIS to view the point cloud.

Link to the lidar report.

Link to view the point cloud, using the Entwine Point Tile (EPT) format, in the 3D Potree viewer.

Link to the kmz that displays the dataset footprint.

The ABGPS, inertial measurement unit (IMU), and raw scans are collected during the LiDAR aerial survey. The ABGPS monitors the xyz position of the sensor and the IMU monitors the orientation. During the aerial survey, laser pulses reflected from features on the ground surface are detected by the receiver optics and collected by the data logger. GPS locations are based on data collected by receivers on the aircraft and base stations on the ground. The ground base stations are placed no more than 40 km radius from the flight survey area.

The ABGPS, IMU, and raw scans are integrated using proprietary software developed by Leica Geosystems called IPAS Pro (Version 1.35). These LiDAR data are then output to a ASPRS Version 1.2 LAS binary format using Leica Geosystems ALSPP post-processing software (Release 2.75 Build #25 ) The LAS version 1.2 file format can be easily transferred from one file format to another. It is a binary file format that maintains information specific to the LiDAR data (return number, intensity value, xyz, etc.). The header file for each dataset is complete as defined by the LAS 1.0 specification.

The unedited data are classified to facilitate the application of the appropriate feature extraction filters. Combinations of proprietary filters are applied as appropriate for the production of bare earth digital elevation models (DEMs). Interactive editing methods are applied to those areas where it is inappropriate or impossible to use the feature extraction filters, based upon the design criteria and/or limitations of the relevant filters. These same feature extraction filters are used to produce elevation height surfaces.

The data was classified as follows:

Class 1 =Processed, but unclassified

Class 2 = Bare-earth ground

Class 3 = Low Vegetation is 0-5 feet

Class 4 = Medium Vegetation is 5-20 feet

Class 5 = High Vegetation is 20 feet or more

Class 6 = Buildings, bridges, other manmade structures

Class 7 = Noise (low or high, manually identified, if needed

Class 9 = Water

Class 10 Ignored Ground (Breakline Proximity)

Class 14 = Ground Overlap

Class 15 = Defualt Overlap

Class 17 = Bridge Decks

Filtered and edited data are subjected to rigorous QA/QC, A series of quantitative and visual procedures are employed to validate the accuracy and consistency of the filtered and edited data. Ground control is established by DAS and GPS-derived ground control points (GCPs) in various areas of dominant and prescribed land cover. These points are coded according to land cover, surface material, and ground control suitability. A suitable number of points are selected for calculation of a statistically significant accuracy assessment, as per the requirements of the National Standard for Spatial Data Accuracy. A spatial proximity analysis is used to select edited LiDAR data points within a specified distance of the relevant GCPs. A search radius decision rule is applied with consideration of terrain complexity, cumulative error, and adequate sample size. Accuracy validation and evaluation is accomplished using proprietary software to apply relevant statistical routines for calculation of Root Mean Square Error (RMSE) and the National Standard for Spatial Data Accuracy (NSSDA), according to Federal Geographic Data Committee (FGDC) specifications.

The Office for Coastal Management (OCM) downloaded 775 laz files from the USGS rockyweb site for the NRCS_Christian_County_IL dataset. The data were in IL State Plane West, NAD83 HARN, US survey feet coordinates and NAVD88 (Geoid12B) elevations in feet. The points were classified as 1- Unclassified, 2 - Ground, 3 - Low Vegetation (0 - 5 ft), 4 - Medium Vegetation (5 - 20 ft), 5 - High Vegetation (20 ft or more), 6 - Buildings, 7 - Low Noise, 9 - Water, 10 - Ignored Ground, 14 - Overlap Ground, 15 - Overlap Unclassified, 17 - Bridge Deck. The class 14 points were reclassified to 22 and the class 15 points were reclassified to 21. All points were processed to the NOAA Digital Coast Data Access Viewer (DAV) for data provisioning. The classes available on DAV are: 1,2,3,4,5,6,7,9,10,17,21,22.

OCM performed the following processing on the data for Digital Coast storage and provisioning purposes:

1. Internal OCM scripts were run to check the number of points by classification and by flight ID and the gps, elevation, and intensity ranges.

2. Internal OCM scripts were run on the laz files to:

a. Re-classify the Class 14 points to 22 (Overlap Ground) and the Class 15 points to 21 (Overlap Unclassified)

b. Convert from orthometric (NAVD88) elevations in feet to NAD83 (2011) ellipsoid elevations in meters using the Geoid12B model

c. Convert the laz files from IL State Plane West, NAD83 HARN, US survey feet coordinates to geographic coordinates

d. Assign the geokeys, sort the data by gps time and zip the data to database