2013 City and Borough of Juneau, Alaska Lidar

This dataset is LiDAR point cloud data, which encompasses a 100 meter buffer around the Juneau,AK study area, approximately 121,313 acres. Dataset Description: This dataset consists of 1273 .LAS files delineated in 750 x 750 m tiles and named as specified by the client. Each .LAS file contains LiDAR point information, which has been calibrated, controlled, and classified. LAS points contain RGB values from orthoimagery mosaics. Normalized intensity values are represented in the intensity field in this version of the point cloud. Ground Conditions: LiDAR acquisition of near shore areas was prioritized to coincide with the lowest tides possible, within constraints of daily local weather patterns. Leaf-off, no snow conditions were targeted in all other areas given the diverse terrain represented in the study area.

The LAZ files have vertical georeferencing using the EPSG 5866 code for mean lower low water. However, this code is for depth while the data is in height. There was no appropriate code for MLLW height at the time.

Data was collected to aid CBJ in assessing the topographic and geophysical properties of the study area to support municipal planning, habitat assessments, and general development in the region. The LiDAR point cloud data were used to create classified LiDAR LAS files, normalized intensity images, 3D breaklines, bare earth DEM, bare earth hydro-flattened DEM, High Hit DSM, Vegetation height model, bridge footprints, 0.5m contours, and a mean high water contour. Data were also used to rectify 4-band orthophotos. The contract for this project was funded by the Coastal Impact Assistance Program through the Alaska Department of Commerce, Community, and Economic Development as part of Grant # 10-CIAP-0009, titled 'Habitat Mapping and Analysis Project.'

All processing was completed by WSI. In some areas of heavy vegetation or forest cover, there may be relatively few ground points in the LiDAR data. TINing the points produces large triangles and hence the elevations may be less accurate within such areas. Elevation values for open water surfaces are derived from waters edge breaklines. Triangles were created across water surfaces by interpolating from the nearest breakline elevation points. RandM Engineering Inc. (Mark A. Johnson - AKPLS#7570) provided the Mean Lower Low Water (MLLW) elevation adjustment for all monuments used for the project. These MLLW elevations were determined by running level loops from tidal benchmarks with published MLLW elevations to each monument. Differences between the orthometric elevations of each monument on Geoid 12A and the MLLW elevations can be found in Appendix B of the Juneau LiDAR data report. The average MLLW adjustment was approximately 1.045m with a standard deviation of 0.066m. As a result of being calibrated using the ellipsoidal MLLW elevations instead of the normal ellipsoidal elevations, the LiDAR data was adjusted to the MLLW vertical datum.

10272

LAS 1.2 format (classes 2,3,4,5,6,7,8,9,10,19,20,21,22,23,24,25,27)

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Any conclusions drawn from the analysis of this information are not the responsibility of RandM Engineering Inc., Watershed Sciences Inc (Quantum Spatial), Alaska DGGS, NOAA, 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=4813

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

No restrictions apply to this data.

In some areas of heavy vegetation or forest cover, there may be relatively few ground points in the LiDAR data. TINing the points produces large triangles and hence the elevations may be less accurate within such areas. Elevation values for open water surfaces are derived from waters edge breaklines. Triangles were created across water surfaces by interpolating from the nearest breakline elevation points. RandM Engineering Inc. (Mark A. Johnson - AKPLS#7570) provided the Mean Lower Low Water (MLLW) elevation adjustment for all monuments used for the project. These MLLW elevations were determined by running level loops from tidal benchmarks with published MLLW elevations to each monument. Differences between the orthometric elevations of each monument on Geoid 12A and the MLLW elevations can be found in Appendix B of the Juneau LiDAR data report. The average MLLW adjustment was approximately 1.045m with a standard deviation of 0.066m. As a result of being calibrated using the ellipsoidal MLLW elevations instead of the normal ellipsoidal elevations, the LiDAR data was adjusted to the MLLW vertical datum.

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. These data depict the heights at the time of the survey and are only accurate for that time.

The cumulative orthophoto horizontal accuracy (RMSE) for the Juneau Priority Area 1 was 0.55 feet (0.17 meters) measured by ground control points and 0.30 feet (0.09 meters) measured by air targets, meeting our accuracy standard of < 3 pixels (0.45 meters); Quantitative Value: 0.17 meters, Test that produced the value: The cumulative orthophoto horizontal accuracy (RMSE) for the Juneau Priority Area 1 was 0.55 feet (0.17 meters) measured by ground control points and 0.30 feet (0.09 meters) measured by air targets, meeting our accuracy standard of < 3 pixels (0.45 meters)

Specifications for this project require that the FVA be 24.5 cm or better AccuracyZ at 95 percent confidence level.; Quantitative Value: 0.059 meters, Test that produced the value: 5.9 cm meters AccuracyZ at 95 percent Confidence Interval. Accuracy was assessed using 3095 ground survey RTK (real time kinematic) points. ; Quantitative Value: 0.072 meters, Test that produced the value: Bare Earth SVA; Quantitative Value: 0.236 meters, Test that produced the value: Brush SVA; Quantitative Value: 0.122 meters, Test that produced the value: Deciduous Forest SVA; Quantitative Value: 0.127 meters, Test that produced the value: Evergreen Forest SVA; Quantitative Value: 0.131 meters, Test that produced the value: Short Grass SVA; Quantitative Value: 0.106 meters, Test that produced the value: Wetland Grass SVA

LAS files include all data points collected. No points have been removed or excluded. Shaded relief images have been visually inspected for data errors such as pits, border artifacts, and shifting. LiDAR flight lines have been examined to ensure consistent elevation values across overlapping flight lines. The raw point cloud is of good quality and data passes Fundamental Vertical Accuracy specifications. Please see the LiDAR data report for a discussion of the statistics related to this dataset.

Data cover the entire area specified for this project.