2015 FEMA Lidar: Marinette County, WI

Lidar collection dates.

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.

This graphic displays the footprint for this lidar data set.

Link to data set report.

Link to data set report.

Link to the breaklines.

Using one Leica ALS70 (lidar) system on board a Cessna 310 aircraft, high density data, at a nominal pulse spacing (NPS) of 1.0 meter, were collected for this task order (approximately 1, square miles). AGL = 7800 feet - Aircraft Speed = 150 Knots, Field of View (Full) = 40 degrees, Pulse Rate = 230 kHz, Scan Rate = 34.4 Hz, with an average side lap of 25%. Multiple returns were recorded for each laser pulse along with an intensity value for each return. Seven (7) missions were flown between April 15, 2015 and April 24, 2015. One (1) Global Navigation Satellite System (GNSS) Base Station was used in support of the lidar data acquisition. Specific information regarding latitude, longitude, and ellipsoid height to the L1 phase center is included in the lidar processing report. The geoid used to reduce satellite derived elevations to orthometric heights was GEOID12A. Data for the task order is referenced to the UTM Zone 16N, North American Datum of 1983 (2011) meters, and NAVD88, in US Survey Feet. Once the data acquisition and GPS processing phases are complete, the lidar data was processed immediately to verify the coverage had no voids. The GPS and IMU data was post processed using differential and Kalman filter algorithms to derive a best estimate of trajectory. The quality of the solution was verified to be consistent with the accuracy requirements of the project. The SBET was used to reduce the lidar slant range measurements to a raw reflective surface for each flight line. The ALS70 calibration and system performance is verified on a periodic basis using Woolpert's calibration range. The calibration range consists of a large building and runway. The edges of the building and control points along the runway have been located using conventional survey methods. Inertial measurement unit (IMU) misalignment angles and horizontal accuracy are calculated by comparing the position of the building edges between opposing flight lines. The scanner scale factor and vertical accuracy is calculated through comparison of lidar data against control points along the runway. Field calibration is performed on all flight lines to refine the IMU misalignment angles. IMU misalignment angles are calculated from the relative displacement of features within the overlap region of adjacent (and opposing) flight lines. The raw lidar data is reduced using the refined misalignment angles.

The individual flight lines were inspected to ensure the systematic and residual errors have been identified and removed. Then, the flight lines were compared to adjacent flight lines for any mismatches to obtain a homogenous coverage throughout the project area. The surveyed ground control points provided by Compass Data are used to make vertical adjustments to the data set and to perform the accuracy checks and statistical analysis of the lidar dataset. Supervisory QC monitoring of work ensured consistency of calibration and adjustments in adherence to project requirements across the entire project area. The resulting deliverables for this task order consist of unclassified LAS 1.2 files provided in a tiled format, fgdc metadata, and a post-flight aerial acquisition and calibration report. As part of this report, additional shape files were delivered and include flight line trajectories, planned flight lines, swath index, base station locations, tile index, and buffered AOI.

Tile Size: 1,500m x 1,500m. The tile file name was derived from the southwest corner of each tile.

Data was received in meters horizontally and US survey feet vertically. Automated macro to classify ground points, classify overlap, and apply multiplier to vertical values to convert to meters were run. Manual edits were conducted to ensure accurate classification of ground points and breaklines were digitized for any bodies of water and for any significant cliffs that were encountered. A macro was then run to classify water points within bodies of water and hydro polygons were draped and water bodies with flow were hydro-enforced to show downstream flow. Breaklines were collected over the entire project area along streams greater than 100ft in

width and water bodies greater than2 acres in area. These breaklines were used to define

water points and hydro-flatten the data. 3D Breaklines were collected at breaks in slope to

support production of the 2-foot contours. Breaklines were collected in the full collection

area (including the buffer area).

Final macro was run to convert vertical values back to US Survey Feet and to assign points to delivery classes of:

Class 1 – Default

Class 2 – Ground

Class 7 – Noise ??

Class 9 – Water (Including 1 meter buffer around hydro breaklines)

Class 10 – Ignored Ground (including 1 meter buffer around terrain breaklines)

Class 156 – Overlap/Withheld**

**LP360 was used to apply withheld flag to overlap points that were initially classified to class 12. However, due to data being LAS version 1.2, the overlap flag is not included in the code structure of the files. Therefore, the withheld flag was applied and the points were reclassified to class 28. For an undetermined reason, when the points are subsequently viewed in TerraScan, the class for the withheld points is class 156 instead of class 28. However the withheld flag stayed intact.

OCM retrieved 1,800 las files from WisconsinVIew. Data was received in UTM 16N NAD 83 (2011) meters horizontally and NAVD88 US survey feet vertically. The data were classified as: 1 - Unclassified, 2 - Ground, 7 - Low Noise, 9 - Water, 10 - Ignored Ground, and 28 - Withheld. OCM processed all classifications of points to the Digital Coast Data Access Viewer (DAV). Classes available on the DAV are: 1, 2, 7, 9, 10 and 12 - which were reclassified and still marked as withheld.

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

1. The laszip program was used to convert the files to laz format.

2. An internal OCM script was run to check the number of points by classification and by flight ID and the gps and intensity ranges.

3. Internal OCM scripts were run on the laz files to convert from orthometric (NAVD88) elevations to ellipsoid elevations using the Geoid12A model, to convert from UTM 16N NAD83 (2011) coordinates in meters to geographic coordinates, to convert vertical units from feet to meters, to assign the geokeys, to sort the data by gps time, to change the point classification of 28 to 12, and zip the data to database and to http.