2012 NOAA American Samoa Lidar DEM: Islands of Tutuila, Aunu'u, Ofu, Olosega, Ta'u and Rose Atoll

Light Detection and Ranging (LiDAR) data is remotely sensed high-resolution elevation data collected by an airborne collection platform. This LiDAR dataset is a survey of American Samoa including the islands of Tutuila, Aunu'u, Ofu, Olosega, Ta'u and Rose Atoll. The project area consists of approximately 75 square miles. The project design of the LiDAR data acquisition was developed to support a nominal post spacing of 1.0 meter or better (1.0 meter GSD). GMR Aerial Surveys Inc. d/b/a Photo Science, Inc. acquired 108 flight lines in 7 lifts between June 2012 and July 2012. This collection was for NOAA Office for Coastal Management (OCM). The data collection was performed with a Beechcraft King Air 90 twin engine aircraft (tail number N87E) utilizing an Optech Gemini sensor; collecting multiple return x, y, and z as well as intensity data.

The collection conditions were cloud and fog-free between the aircraft and the ground; streams must be within their banks; and low tide acquisition if at all possible.

Data voids within a single swath were avoided whenever possible. Acceptable void areas are caused by a water body; areas of low near infrared (NIR) reflectivity such as asphalt or composition roofing and where appropriately filled in by another swath. Unfortunately, during the LiDAR acquisition there were a few mountain peaks where the clouds never lifted high enough to collect LiDAR.

In order to post process the LiDAR data to meet task order specifications, Photo Science, Inc. established control points that were used to calibrate the LiDAR to known ground locations established on Tutuila. Please see the survey report for more details in the URLs section.

The dataset was developed based on a horizontal projection/datum of UTM NAD83 (PACP00), UTM Zone 2, meters. The vertical datum used during the collection, varied by island. NAVD88 (ASVD02), meters was used for the island of Tutuila (and Aunu'u). NAVD1988 (GEOID09), meters was used for the islands of Ofu, Olosega and Tau. Rose atoll was adjusted from Ellipsoid heights to a mean low water (MLW) datum (see lineage steps for details).

The project was developed by the National Oceanic and Atmospheric Administration's (NOAA) Office for Coastal Management in Charleston, SC to collect and deliver topographic elevation point data derived from multiple return light detection and ranging (LiDAR) measurements for American Samoa including islands of Tutila, Aunu'u, Ofu, Olosega, Ta'u and Rose Atoll. Data are intended for use in coastal management decision making.

Classified LAS files are used to show the manually reviewed bare earth surface. This allows the user to create Intensity Images, Breaklines and Raster DEM.

There were seven lifts flown out of Pago Pago International Airport for Tutuila and Aunuu and Fitiuta Airport for Ofu, Olosega,

Tau and Rose Atoll collection.

Base stations were set up at the airports and sensor Serial Number 246 was used for all flights:

June 25, 2012 A

June 25, 2012 B

June 25, 2012 C

June 27, 2012

July 5, 2012 A

July 5, 2012 B

July 5, 2012 C

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

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

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=8543

This data set is dynamically generated based on user-specified parameters.

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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.

MicroStation Version 8; TerraScan Version 12; TerraModeler Version 12; GeoCue Version 2012;

ESRI ArcGIS 10.1; Global Mapper 14.1; Optech DashMAP 5.2000

The project area required LiDAR to be collected on 1.0 meter GSD or better and processed to meet a bare earth vertical accuracy

of 15.0 centimeters RMSEz or better.

Collected to meet four feet RMSE or better.

The reported RMSEz value was determined using the calibration control points, and not the Blind Control. The calibration control

points are the same points that were used to remove any bias in the dataset before bare earth editing.

The islands control were measured with Ofu and Olosega; Tau; and Tutuila and Aunuu. The RMSE for each island:

Ofu and Olosega RMSE 0.074 m.

Tau RMSE 0.072 m.

Tutuila and Aunuu RMSE 0.067 m.

The listed RMSEz value shown below was calculated from the ground (ASPRS Class 2) data in the final Classified LAS files

and is an average of the above RMSE values.

; Quantitative Value: 0.071 meters, Test that produced the value: RMSE in meters, as calculated from Classified LAS files

Datasets contain complete coverage of project area and tiles.

Raw Flightlines, Classified LAS files, Breaklines, and Raster DEMs were tested by Photo Science for vertical accuracy.

Although collected on a tile-by-tile basis, breaklines are merged together to produce a single deliverable dataset. Checks are done to

ensure that the data is seamless from one tile to the next before being combined and that breaklines meeting the project requirements

have been collected across the entire project area.

Combining the breaklines with LiDAR data to create other deliverables is another check of the data. All data are seamless from one

tile to the next, no gaps or no data areas whenever possible. Unfortunately, during the LiDAR acquisition there were a few mountain

peaks where the clouds never lifted high enough to collect LiDAR.