2022 - 2024 NRCS QL2 Lidar DEM: Native Alaskan Villages

Original Product: Hydro-flattened Digital Elevation Model (DEM) data covering the Alaska Native Villages Lidar project area.

Original Geographic Extent:

AK_NativeAKVillages_1 (Work Unit 300198) - This block encompasses an area covering approximately 60,583 acres and includes the villages of Golovin, Atmautluak, Tuntutuliak, and Kwigillingok

AK_NativeAKVillages_2 (Work Unit 300199) - This block encompasses an area covering approximately 35,677 acres and includes the villages of Akiak and Shaktoolik

AK_NativeAKVillages_3 (Work Unit 300200) - This block encompasses an area covering approximately 73,362 acres and includes the villages of McGrath and Tyonek

AK_NativeAKVillages_4 (Work Unit 300201) - This block encompasses an area covering approximately 16,079 acres and includes the village of Fort Yukon

AK_NativeAKVillages_5 (Work Unit 300450) - This block encompasses an area covering approximately 8,447 acres and includes the village of Levelock

AK_NativeAKVillages_7 (Work Unit 300843) - This block encompasses an area covering approximately 13,489 acres and includes the village of Savoonga

AK_NativeAKVillages_8 (Work Unit 300844) - This block encompasses an area covering approximately 40,274 acres and includes the villages of Chefornak and Tununak

Original Dataset Description: Lidar flight line swaths were processed to create classified LAS 1.4 files delineated in 1500m x 1500m tiles tiles. Each LAS file contains lidar point information, which has been calibrated, controlled, and classified. Class 2 (ground) lidar points in conjunction with the hydro breaklines were used to create 1 meter hydro-flattened Raster DEMs delineated in 1500m x1500m tiles tiles. Non-Vegetated Vertical Accuracy (NVA) was assessed using check points located on bare earth in clear, unobstructed areas. Vegetated Vertical Accuracy (VVA) was assessed using check points in landcover types. Additional products include classified LAS files, intensity images, highest hit surface models, and 3D breaklines of rivers and lakes within the study area.

Ground Conditions: Ground condition was free of snow and acquisition occurred free of smoke, fog and cloud cover.

This metadata record supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV). For this data set, the DAV is leveraging the GeoTIFF files hosted by USGS on Amazon Web Services.

The purpose of the lidar data was to produce a high accuracy 3D dataset that meets all necessary standards laid out by the 3D Elevation Program and the Alaska Native Villages Lidar contract. The lidar point cloud data were used to create classified lidar LAS files, intensity images, hydro-flattened DEMs, highest hit surface models, and 3D breaklines of rivers and lakes within the study area.

Raster File Type = TIFF

Bit Depth/Pixel Type = 32-bit float

Raster Cell Size = 1 meter

Interpolation or Resampling Technique = Triangulated Irregular Network

Required Vertical Accuracy = 19.6 cm NVA

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

AK_NativeAKVillages_1 (Work Unit 300198) - Villages of Golovin, Atmautluak, Tuntutuliak, and Kwigillingok

AK_NativeAKVillages_2 (Work Unit 300199) - Villages of Akiak and Shaktoolik

AK_NativeAKVillages_3 (Work Unit 300200) - Villages of McGrath and Tyonek

AK_NativeAKVillages_4 (Work Unit 300201) - Village of Fort Yukon

K_NativeAKVillages_5 (Work Unit 300450) - Village of Levelock

AK_NativeAKVillages_7 (Work Unit 300843) - Village of Savoonga

AK_NativeAKVillages_8 (Work Unit 300844) - Villages of Chefornak and Tununak

To the extent possible under law, the U.S. Government has waived all copyright and related or neighboring rights to this dataset.

Data is available online for bulk and custom downloads.

None

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

Lidar horizontal accuracy is a function of Global Navigation Satellite System (GNSS) derived positional error, flying altitude, and INS derived attitude error. The maximum GNSS positional error was derived from the laser trajectory using NV5's proprietary LAS processing software, Las Monkey. The obtained RMSEr value is multiplied by a conversion factor of 1.7308 to yield the horizontal component of the National Standards for Spatial Data Accuracy (NSSDA) reporting standard where a theoretical point will fall within the obtained radius 95 percent of the time.

AK_NativeAKVillages_1

The villages in this project had a flying altitude of 2500 meters and a GNSS positional error of 0.023 meters. In addition to these parameters, the villages in this block had an IMU error of 0.003 decimal degrees, which was produced to meet a 0.407 m horizontal accuracy at the 95% confidence level.

AK_NativeAKVillages_2, AK_NativeAKVillages_3, AK_NativeAKVillages_4

The villages in this project had a flying altitude of 2500 meters and a GNSS positional error of 0.023 meters. In addition to these parameters, the villages in this block had an IMU error of 0.002 decimal degrees, which was produced to meet a 0.273 m horizontal accuracy at the 95% confidence level.

AK_NativeAKVillages_5

Based on a flying altitude of 2500 meters, a GNSS error of 0.023 meters, and an IMU error of 0.001 degrees, the Levelock village was produced to meet a horizontal accuracy of 0.141 meters, at the 95% confidence level.

AK_NativeAKVillages_7, AK_NativeAKVillages_8

Based on a flying altitude of 2478 meters, a GNSS error of 0.019 meters, and an IMU error of 0.002 degrees, the villages in these blocks were produced to meet a horizontal accuracy of 0.270 meters, at the 95% confidence level.

For more information see the lidar reports. The links to these reports are provided in the URL section of this metadata record.

This data set was produced to meet ASPRS Positional Accuracy Standard for Digital Geospatial Data (2014) for a 10-cm RMSEz Vertical Accuracy Class. The specifications require that classified Non-vegetated Vertical Accuracy (NVA) be computed from the derived DEMs. Vegetated Vertical Accuracy (VVA) is also to be computed from the derived DEMS. Specifications for this project require that the VVA be 0.300 meters or better AccuracyZ at the 95th percentile. Elevations of the derived bare earth DEMs were compared to the elevation values of the surveyed NVA check points.

USGS Determined DEM Vertical Accuracy

Tested NVA RMSEz = 3.55 cm

Tested 95th percentile value for VVA is : 26.39 cm

For more information see the USGS project report and the lidar reports. The links to these reports are provided in the URL section of this metadata record.

A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist. The raw point cloud is of good quality and data passes Non-Vegetated Vertical Accuracy specifications.

DEM files were tested by NV5 for vertical accuracy. All data is seamless from one tile to the next, no gaps or no data areas.

The NOAA Office for Coastal Management (OCM) ingested references to the USGS GeoTIFF files that are hosted on Amazon Web Services (AWS), into the Digital Coast Data Access Viewer (DAV). The DAV accesses the raster data as it resides on AWS.