2015 Lidar DEM: Municipality of Anchorage, AK

The base LiDAR deliverables will conform to USGS LBS specifications V1.4 for Quality Level 2 (QL2) data.

The QL2 requires collection of 2 points per square meter (ppsm), nominal LiDAR pulse spacing of no greater

than 0.7 meter for 463 square miles and 4 PPSM for 494 sq. miles and a vertical accuracy of better than 10-cm

RMSE. (Merrick will provide data to a 9.25cm vertical accuracy in the interest of meeting a 1 foot contour

accuracy specification and this will still meet the QL2 specification).

These files contain rasterized topographic lidar elevations at a 3 ft grid spacing.

The NOAA Office for Coastal Management (OCM) downloaded this DEM data from the AK DGGS site, processed it, and made it available on the NOAA Digital Coast. In addition to this bare earth digital elevation model (DEM) raster data, lidar point and breakline data are also available. Links to these data are located in the URL section of this metadata record. The breakline data has not been reviewed by OCM and is made available at the user's discretion.

957 square miles of 2 ppsm and 4 ppsm LiDAR to USGS QL2 specifications to support the Municipality base mapping efforts.

The lidar data that these DEM data were created from were:

Fully Classified LAS formatted files

LAS 1.4 format or as required by MOA

Classification of the LiDAR point cloud in accordance with the

following classification scheme:

Class 1 = Processed, but Unclassified

Class 2 = Bare-earth Ground

Class 7 = Low point (noise)

Class 9 = Water

Class 10 = ignored ground (near a Breaklines)

Class 17 = Bridges Decks

LAS 1.4 format or as required by MOA

Classification of the LiDAR point cloud in accordance with the following classification scheme:

Class 1 = Processed, but Unclassified

Class 2 = Bare-earth Ground

Class 7 = Low point (noise)

Class 9 = Water

Class 10 = ignored ground (near a Breaklines)

Class 17 = Bridge Decks

LAS 1.4 format or as required by MOA Classification of the LiDAR point cloud in accordance with the following classification scheme: Class 1 = Processed, but Unclassified Class 2 = Bare-earth Ground Class 7 = Low point (noise) Class 9 = Water Class 10 = ignored ground (near a Breaklines) Class 17 = Bridge Decks

Any conclusions drawn from the analysis of this information are not the responsibility of Merrick, the Municipality of Anchorage, the NOAA Office for Coastal Management, or its partners.

Users may access the data from two links. Custom download and bulk download options are available.

None

Users should be aware that temporal changes may have occurred since this data set was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these data for critical applications without a full awareness of its limitations.

Microsoft Windows Vista Version 6.1 (Build 7601) Service Pack 1; ESRI ArcCatalog 9.3.1.4095

This data set was produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 42.98 cm RMSEx / RMSEy Horizontal Accuracy Class which equates to Positional Horizontal Accuracy = +/- 74.68 cm at a 95% confidence level.

This data set was tested to meet ASPRS Positional Accuracy Standard for Digital Geospatial Data (2014) for a 10.0-cm RMSEz Vertical Accuracy Class. Actual NVA accuracy (55 NVA check points) was found to be RMSEz = 6.965 cm, equating to +/- 13.651 cm at the 95% confidence level. Actual VVA accuracy (45 VVA check points) was found to be +/- 15.180 cm at the 95th percentile.

This dataset contains unclassified returns of the LIDAR sensor. The sensor data was verified in MARS software to ensure complete coverage.

Calibrations of the LIDAR flightline data are performed; this process is known as boresighting. The flightlines are compared to evaluate both their relative and absolute accuracies.