2024 USGS Lidar DEM: FEMA Region 9 Southeast California

Original Product: 0.5-meter bare-earth raster digital elevation model (DEM) data tiles in GeoTIFF format.

Original Dataset Description: CA_FEMAR9Southeast_D24 lidar project called for the planning, acquisition, processing, and production of derivative products of QL1 lidar data to be collected an aggregate nominal pulse spacing (ANPS) of 0.35-meters and 8 points per square meter (ppsm). Project specifications were based on the U.S. Geological Survey National Geospatial Program Lidar Base Specification 2024, Revision, and the American Society of Photogrammetry and Remote Sensing (ASPRS) Positional Accuracy Standards for Digital Geospatial Data, Edition 2, Version 2 (2024). DEM data was delivered as processed GeoTIFF files formatted to individual 1,000-meters x 1,000-meters tiles.

CA_FEMAR9_Southeast_1 (Work Unit 301009)

Geographic Extent: Approximately 3826 square miles in southern California.

NOTE: Temporal polygons were generated for 8 areas in WU1 totaling 0.27 square miles where different acquisition dates caused visible temporal changes in the data. Low confidence polygons were generated for 35 areas in WU1 totaling 0.93 square miles where sensor drop-out resulted in single swath areas and diminished point density.

CA_FEMAR9_Southeast_2 (Work Unit 301010)

Geographic Extent: Approximately 3768 square miles in southern California.

NOTE: The Temporal polygons were generated for 26 areas in WU2 totaling 0.65 square miles where different acquisition dates caused visible temporal changes in the data. Low confidence polygons were generated for 19 areas in WU2 totaling 0.46 square miles where sensor drop-out resulted in single swath areas and diminished point density.

CA_FEMAR9_Southeast_3 (Work Unit 301011)

Geographic Extent: Approximately 3784 square miles in southern California.

NOTES: To safely and efficiently acquire the data at the required point density, multiple flight blocks were planned and flown in different directions with varying amounts of sidelap due to the complexity of the terrain. The flight blocks were planned independently of the work unit. The temporal polygons were generated in areas where earth-moving occurred across acquisition dates. Low Confidence Polygon: The lidar data for the CA_FEMAR9Southeast_3_D24 project was flown from April to December in 2024. To safely and efficiently acquire the data at the required point density, multiple flight blocks were planned and flown in different directions with varying amounts of sidelap due to the complexity of the terrain. The flight blocks were planned independently of the work unit. During the calibration process, the complexity of the acquisition led to areas where vertical offsets between the acquisition blocks where present which can be seen as seamlines in the DEMs. Efforts were made to improve the offset, but seamlines of 3-10 centimeters are visible on tile edges and are especially visible in areas of flat open terrain. Low confidence polygons have been drawn around these areas.

CA_FEMAR9_Southeast_4 (Work Unit 301012)

Geographic Extent: Approximately 3876 square miles in southern California.

NOTE: Low confidence polygons were generated for 14 areas in WU4 totaling 2 square miles where sensor drop-out resulted in single swath areas and diminished point density.

CA_FEMAR9_Southeast_5 (Work Unit 301013)

Geographic Extent: Approximately 3929 square miles in southern California.

NOTE: Due to open water there is no tiled LAZ, INT, SSI or MSHR product for the forty-two tiles. The temporal polygons were generated in areas where snow is present but does not represent lowest surface in the DEM so Class 1 was used to denote higher snow surface, and in areas where there is a noticeable signature in SSIs due to temporal differences. Low confidence polygons were generated for 58 areas in WU5 totaling 1.3 square miles where sensor drop-out resulted in single swath areas and diminished point density.

CA_FEMAR9_Southeast_6 (Work Unit 301014)

Geographic Extent: Approximately 3819 square miles in southern California.

NOTE: The area covered by this work unit is known to have significant snow fall and snow melt year over year, but given the high reflectivity of the desert terrain, it can be difficult to clearly distinguish snow from the surrounding terrain. Woolpert reviewed the intensity imagery and manually digitized areas that are 2 acres or greater of what we interpret as snow. Woolpert used their best judgement to distinguish between snow and surrounding terrain due to their similar intensity values within the work unit. The temporal polygons were generated in areas where snow is present but there was significant snow melt across acquisition dates. The temporal polygons have been provided as a shapefile. The low confidence polygon was generated for an area of approximately 830 square meters where a sensor dropout occurred; this area could potentially be a seasonal water body and is seen as a depression in open source imagery.

CA_FEMAR9_Southeast_7 (Work Unit 301121)

Geographic Extent: Approximately 5.45 square miles in southern California.

NOTE 1: This work unit consists of targeted reflights along the project's perimeter in several isolated areas, where point density was insufficient due to incomplete coverage from the 50% sidelap. The areas addressed in this work unit are adjacent to CA_FEMAR9Southeast_3_D24 and CA_FEMAR9Southeast_4_D24. Because this work unit's tiles are scattered and not contiguous, normal accuracy testing could not be performed as an independent work unit.

NOTE 2: While the task order required hydro-flattened bare-earth DEMs, there were no hydrobreaklines present in this work unit to be collected.

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 this project is to obtain high quality elevation data to support the Federal Emergency Management Agency (FEMA) Risk Mapping, Assessment and Planning (MAP) program, the Bureau of Land Management (BLM), and the USGS 3DEP and EarthMRI missions.

USGS Contract No. 140G0221D0013, Task Order No. 140G0224F0090, Project Name: CA FEMAR9Southeast D24. Contractor: Woolpert.

Raster File Type = TIFF

Bit Depth/Pixel Type = 32-bit float

Raster Cell Size = 0.5-meter

Interpolation or Re-sampling 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.

CA_FEMAR9_Southeast_1 (Work Unit 301009)

CA_FEMAR9_Southeast_2 (Work Unit 301010)

CA_FEMAR9_Southeast_3 (Work Unit 301011)

CA_FEMAR9_Southeast_4 (Work Unit 301012)

CA_FEMAR9_Southeast_5 (Work Unit 301013)

CA_FEMAR9_Southeast_6 (Work Unit 301014)

CA_FEMAR9_Southeast_7 (Work Unit 301121)

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.

TerraSolid v24, GDAL 3.8.1, Esri ArcMap v10.8, Global Mapper v25, and LAStools 240220.

This data set was calculated using the formula provided in section 7.6 of the ASPRS Positional Accuracy Standard for Digital Geospatial Data Edition 2, Version 2 of 2024. The calculated horizontal positional accuracy was found to be RMSEH = 25.0-cm.

This data set was produced to meet ASPRS Positional Accuracy Standard for Digital Geospatial Data (2014) for a 10-cm RMSEz Vertical Accuracy Class.

USGS Determined DEM Vertical Accuracy:

Non-Vegetated Vertical Accuracy (NVA) = 6.6 cm RMSE

Vegetated Vertical Accuracy (VVA) = 14.51 cm at 95th Percentile

A visual qualitative assessment was performed to ensure data completeness.

Data covers the entire area specified for this project.

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.