Data Management Plan

This metadata record describes the classified point cloud for the 2017 Texas Coastal LiDAR project spanning one of two areas of interest (AOIs). The Western Block AOI covers approximately 289 square miles, including the cities of Liberty, Hankamer, and Anahuac in southeast Texas. This AOI was collected to meet the density of 8 points per meter.

The Eastern Block covers approximately 841 square miles, including the cities of Beaumont, Port Arthur, and Nederland in southeast Texas. The AOI was collected to meet the density of 4 points per meter. Total area covers equals approximately 1.130 square miles.

Sanborn Map Company was contracted by Texas Water Development Board (TWDB) in cooperation with the Trinity River Authority (TRA) to perform 2017 LiDAR aerial surveys of Texas coastal area of about 1130 square miles. Collections was completed utilizing multi-return systems, Light Detection and Ranging (LiDAR) data in the form of 3-dimensional positions of a dense set of mass points between February 22nd and March 23rd, 2017. ALS70 LiDAR was flown to produce four (4) points and eight (8) points per square meter return density or 0.5 meters and 0.35 meters respectively Nominal Point Spacing (NPS)

Process Steps:

• 2017-01-01 00:00:00 - 8PPM LiDAR data was collected over the West Texas AOI. Multiple returns were recorded for each laser pulse along with an intensity value for each return. The data acquisition occurred in ten missions between March 15th and March 23rd, 2017. During the LIDAR campaign, the Sanborn field crew conducted a GPS field survey to establish final coordinates of the ground base stations for final processing of the base-remote GPS solutions. (Citation: LiDAR Data)
• 2017-01-01 00:00:00 - Airborne GPS data was differentially processed and integrated with the post processed IMU data to derive a Smoothed Best Estimate of Trajectory (SBET). IMU data provides information concerning roll, pitch and yaw of collection platform during collection event. IMU information allows the pulse vector to be properly placed in 3D space allowing the distance from the aircraft reference point to be properly positioned on the elevation model surface. The SBET was used to reduce the LiDAR slant range measurements to a raw reflective surface for each flight line. Airborne GPS is differentially processed using the Inertial Explorer software by Leica Geosystems.
• 2017-01-01 00:00:00 - Leica's CloudPro software then combined the SBET and Raw Laser (.scn) files to produce raw point cloud swath data in LAS v1.4 format.
• 2017-01-01 00:00:00 - The raw swath point cloud data was then calibrated using TerraMatch, a TerraSolid software, to correct relative bias in conjoining swaths that include roll, pitch, heading, Scale, and elevation. The swath data is then compared against the calibration control points and adjusted vertically to exceed the vertical accuracy requirements for the project.
• 2017-01-01 00:00:00 - The georeferenced lidar data is then classified and edited in Terrasolid Terrascan software. Data is classified to produce: Class 1: unclassified, Class 2: ground, Class 3: low veg, Class 4: med veg, Class 5: high veg, Class 6: building, Class 7: low point, Class 9: water, Class 10: ignored ground, Class 13: bridge deck, Class 14: culverts
• The NOAA Office for Coastal Management (OCM) retrieved 1,130 laz files from the Texas Natural Resources Information System (TNRIS.org). The files were in UTM 15N NAD83 (2011) meters horizontally, and NAVD88 Geoid12b meters vertically. OCM segregated the Western and Eastern portions and processed them as separate datasets for provisioning. 1. An internal OCM script was run to check the number of points by classification and by flight ID and the gps and intensity ranges. 2. Internal OCM scripts were run on the laz files to convert from orthometric (NAVD88) elevations to NAD83 (2011) ellipsoid elevations using the Geoid 12b model, to convert from UTM Zone 15 North NAD83 (2011) coordinates in meters to geographic coordinates, to assign the geokeys, to sort the data by gps time and zip the data to database and to http.

Data is available online for bulk or custom downloads

Data is backed up to tape and to cloud storage.