2017 USGS Lidar DEM: Chenier Plain, LA

Product: These are Digital Elevation Model (DEM) data for LA Chenier Plain Lidar 2017 B16 Project Level as part of the required deliverables for LA Chenier Plain Lidar 2017 B16 project. Class 2 (ground) lidar points in conjunction with the hydro breaklines and bridge breaklines were used to create a 1 meter hydro-flattened Raster DEM.

Geographic Extent: AOI was located along an area of coastal Louisiana referred to as Chenier Plain, which includes portions of Calcasieu, Cameron, Vermillion, Iberia, and St. Mary Parishes. The area of interest covered approximately 2942 square miles. Dataset Description: LA Chenier Plain Lidar 2017 B16 project called for the planning, acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.70 meter. Project specifications are based on the U.S. Geological Survey National Geospatial Program Lidar Base Specification, Version 1.2. The data was developed based on a horizontal projection/datum of NAD83 (2011), UTM Zone 15N, Meter and vertical datum of NAVD88 (GEOID12B), Meter. Lidar data was delivered as: flightline-extent raw LAS v1.4 swaths, classified point cloud LAS v1.4 files formatted to 3817 individual 1,500 m x 1,500 m tiles in NAD83 (2011), UTM Zone 15N, Meter. Derivatives were produced as tiled; Bare Earth Surface DEMs, Digital Surface Models, Intensity Images; all tiled to the same 1,500 m x 1,500 m schema.

Ground conditions: Lidar was collected in Winter of 2017 by Aerial Services, Inc. (ASI), and WOOLPERT. The Chenier Plain Wetland areas contain hundreds of impoundments related to aquaculture operations. These fields are flooded and contained within the impoundments on a semi-permanent basis, including during the Chenier Plain lidar acquisition timeframe. This is an understood and accepted acquisition condition. Furthermore, impoundments equal to or greater than 2 acres are treated as hydrologically flattened features within the data deliverables. Tidal Restriction: The following tide gauges were considered suitable for prediction of regional water levels within the AOI; Sabin Pass North, TX NOS (8770570), Calcasieu Pass, LA NOS (8768094), Freshwater Canal Locks, LA NOS (8766072), and Amerada Pass, LA NOS (8764227). Water levels at flight time shall were below -0.10 meters (mean seal level) for the Calcasieu Pass, LA tide gauge (8768094) in the west and -0.10 meters (mean seal level) for the Amerada Pass, LA tide gauge (8764227). Meteorological: Acquisition did not occur after passage of a moderate to strong high-pressure system generating northerly winds in excess of five (5) knots. In addition, it is noted switching of winds from WNW to ENE is a tipping point for switching from wind driven marsh drainage to marsh flooding. Ground Conditions: Within the extreme eastern AOI (swamp and fresh to intermediate marsh occurring northeast of Marsh Island and bordering East Cote Blanche Bay) Lidar was not acquired when the Lower Atchafalaya River stage was less than 4 feet as determined by the latest measurements taken at gauge (USGS 07381605) at Morgan City.

Lidar was not acquired when regional precipitation driven flooding occurred in local rivers with significant impact to wetland impoundments located throughout the entire Chenier Plain west of Cote Blanch Bay. The following local rivers shall be monitored for flood conditions; Vermillion, Mermentau, Calcasieu, and Sabine rivers. In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Woolpert established a total of 68 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. Additional independent accuracy checkpoints were collected (94 NVA points and 75 VVA points) and used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

The NOAA Office for Coastal Management (OCM) downloaded the LA_Chenier_Plain_2017 Digital Elevation Model (DEM) files from this USGS site: ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/OPR/ and processed the data to the Data Access Viewer (DAV) and https.

In addition to these bare earth Digital Elevation Model (DEM) data, the lidar point data that these DEMs were created from, are also available. These data are available for custom download at the link provided in the URL section of this metadata record.

Hydro breaklines are also available. These data are available for download at the link provided in the URL section of this metadata record. Please note that these products have not been reviewed by the NOAA Office for Coastal Management (OCM) and any conclusions drawn from the analysis of this information are not the responsibility of NOAA or OCM.

The Chenier Plain QL2 light detection and ranging (lidar) acquisition updates 15+ year old QL4 equivalent topographic lidar for an area representing approximately half of the Mississippi River Delta Plain Complex. The Chenier Plain has incurred direct-surge induced wetland loss impacts from Hurricane Rita (2005) and from Hurricane Ike (2008) as well as economic losses to the local population and surrounding areas. The lidar update will provide an elevation base for assessing current conditions as well as providing a solid data platform for monitoring the impacts of future episodic events, from tropical cyclones or other potential inundation events within the region.

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 = NVA

The information contained in these data is dynamic and may change over time. The data are not better than the original sources from which they were derived. It is the responsibility of the data user to use the data appropriately and within the limitations of the data for which it was requested and prepared, in general, and these data in particular. The related graphics are intended to aid the data user in acquiring relevant data. It is not appropriate to use the related graphics as data. Woolpert gives no warranty, expressed or implied, as to the accuracy, reliability, or completeness of these data. It is strongly recommended that these data are directly acquired from a Woolpert server, and not indirectly through other sources which may have changed the data in some way. Although these data have been processed successfully upon Woolpert’s computer system, no warranty, expressed or implied, is made regarding the utility of the data on another system, or for general or scientific purposes; nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data.

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

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.

Produced to meet 0.355 meters horizontal accuracy at 95 percent confidence level. Lidar system specifications are available in the project report.

LAS data covering the Chenier Louisiana Lidar Task Order was compared to independent survey control points to determine the NVA of the LAS Swath and of the Bare-Earth DEM. In addition, this LAS data was compared to independent VVA points.

LAS Swath Non-Vegetated Vertical Accuracy (NVA) Tested 0.122 Meters Non vegetated vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using 0.062 Meters (RMSEz) x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines.

Raw Swath Non-Vegetated Vertical Accuracy (NVA) Tested 0.122 Meters Non vegetated vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using (RMSEz) 0.062 x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines and tested against the TIN using all lidar points against 94 NVA points.

Bare-Earth DEM Non-Vegetated Vertical Accuracy (NVA) Tested 0.125 Meters Non-Vegetated vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using (RMSEz) 0.064 x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines and tested against the DEM against 94 NVA points.

Vegetated Vertical Accuracy (VVA) Tested 0.121 Meters at the 95th percentile reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines and tested against the DEM against 75 VVA points.

VVA Errors larger than 95th percentile include:

Point 3016, Easting 629296.304, Northing 3308881.652, Z-Error 0.204 Meters

Point 3062, Easting 491457.326, Northing 3322912.322, Z-Error 0.133 Meters

Point 3064, Easting 506371.097, Northing 3292021.418, Z-Error 0.143 Meters

Datasets contain complete coverage of tiles. No points have been removed or excluded. A visual qualitative assessment was performed to ensure data completeness. There are no void areas or missing data. The raw point cloud is of good quality and data passes Non-Vegetated Vertical Accuracy specifications.

Data covers the entire area specified for this project.