Data Management Plan

The Matanuska Susitna Borough LiDAR/Imagery Project covers 3680 sq/mi of the Matanuska-Susitna Borough in Alaska. Project parnters and funding sources include: Coastal Impact Assistance Program, Alaska Industrial Development and Export Authority, Alaska Energy Authority, United States Geological Survey, Matanuska Susitna Borough, United States Army Corps of Engineers, United States Fish and Wildlife Service, The Nature Conservancy, National Oceanic and Atmospheric Administration, Mat-Su Salmon Partnership, and Alaska Pacific University.

This dataset was originally in LAS 1.2 format with a non-standard class table. The format and the class table has been changed. Details are in the processing steps.

The following are the collection parameters and equipment used to create these data sets. The Leica sensor was used for flights in the northern half of the Core Area. All other flights were flown with Optech sensors.

Aircraft: Cessna 310(N7516Q), Piper Navajos (N6GR,T73TM and 812TB), Beechcraft KingAir (N898WW)

Lidar Systems: Optech ALTM Gemini (03SEN145 and 07SEN201) and Leica ALS 70

Approximate Collection Altitude (Above Mean Terrain): Optech--1400 meters, Leica--2200 meters

Ground Speed: Optech--150 kts, Leica--160 kts

Pulse Rate Frequency: Optech--70 kHz, Leica--163.6 kHz

Mirror Scan Frequency: Optech--40 Hz, Leica--41 Hz

Scan Angle (+/-): Optech--17 degrees, Leica--16 Degrees

Beam Divergence: Narrow (0.3 mrad)

Accuracy statements are based on areas of moderate terrain, with points classified as ground. Diminished accuracies are to be expected in areas of extreme terrain and dense vegetation. The accuracy of each point is expected to meet the vertical accuracy standard, derived products may be less accurate in areas of extreme terrain and dense vegetation due to a lesser number of points defining the ground in these areas.

Classified data sets such as this one may have varying posting due to some pulses not reaching the ground.

Original contact information:

Contact Name: Lidar Manager

Contact Org: Aerometric, Inc.

Title: Lidar Manager

Phone: (907) 272-4495

Email: aerometric@aerometric-ak.com

Process Steps:

• 2011-10-12 00:00:00 - Create a smoothed-best estimated trajectory (SBET) of the sensor at a rate of 200 Hz, by integrating the airborne GPS and IMU data The basis of the GPS coordinates were provided to Aero-Metric by Lounsbury, Inc., and were referenced to NAD83 (CORS96) with GEOID09 derived orthometric heights. The maximum baseline distance for this area was 15 km, the average base line length was 5 km. The mean GPS positional accuracy for this area was +/- 0.06 meters.
• 2011-10-12 00:00:00 - Integrate SBET and raw laser data to produce point cloud data in LAS 1.2 format for each flight line.
• 2011-10-12 00:00:00 - Data Calibration: An in-situ calibration was performed using the data collect for this project. The data was classified in each line separately for ground and other common features between lines, such as building roofs. This data was processed in TerraMatch 11.001 (TerraSolid, Ltd.), to compute corrections for roll, pitch, heading, and mirror scale. These corrections are applied in order to minimize discrepancies between flight lines.
• 2011-12-12 00:00:00 - Automated classification of the bare-earth data from the lidar point cloud using a series of algorithms customized for the types of terrain encountered in the project.
• 2012-04-15 00:00:00 - Manual classification of any data which appears to be properly classified using the automated methods.
• 2012-11-20 00:00:00 - Create point cloud data, by tile in LAS 1.2 format with absolute GPS timestamps
• 2013-11-26 00:00:00 - Data for the MatSu Bugoughs was downloaded from matsu.gina.alaska.edu/LiDAR for all areas available
• 2013-12-18 00:00:00 - Data were modified to work with the Digital Coast Data Access Viewer in the following ways: 1) projection was changed from Alaska State Plane to Geographic coordinates; 2) Vertical datum was changed from NAVD88 to NAD83 ellipsoid using NGS GEOID09; 3) the global encoding byte in LAS format was set to indicate adjusted GPS time instead of GPS seconds of the week; and 4) the classification table was modified to avoid classes already used as a standard within Digital Coast. The classification changes were for ground points near breaklines (original class 10 moved to class 2 with user byte set to 2), powerlines (original class 11 moved to class 16), and near ground noise (original class 13 moved to class 15). Data were also compressed to LAZ format using laszip from laszip.org. Data from multiple deliveries were combined and metadata rewritten to cover them all (Caswell Lakes, Core Area, Matanuska, North Susitna, Point MacKenzie, and Willow were the original delivery groups).
• 2021-06-22 00:00:00 - The previous change in the classes was recognized as unhelpful as most software does not provide a way to segment data by the user bytes field for LAS data. Instead of moving the classes back to their original non-standard classes, they were moved to match the LAS1.4 standards as much as possible. This includes moving the points near a breakline to class 20. One class, noise within 1 foot of the ground, is non-standard and was moved to class 77 to conform with the LAS 1.4 requirement that classes below 64 are reserved for ASPRS. The LAS format was also promoted to LAS 1.4. The resulting class table is: classnumber classname 1 Unclassified 2 Ground 3 Low Vegetation 4 Medium Vegetation 5 High Vegetation 6 Building 7 Low Point (noise) 8 Reserved 9 Water 14 Wire-Conductor 17 Bridge Deck 20 Ignored Ground/Bathymetry 77 Near-Ground Noise (Citation: MatSu Point Clouds)

This data can be obtained on-line at the following URL:

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=2609

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