2011 USGS Lidar: Baldwin County, AL

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Survey report for Baldwin County lidar

This graphic shows the lidar coverage for Baldwin Co, Alabama.

QA report for the eastern section of Baldwin County

QA report for the western section of Baldwin County

Date that the source FGDC record was last modified.

Converted from FGDC Content Standards for Digital Geospatial Metadata (version FGDC-STD-001-1998) using 'fgdc_to_inport_xml.pl' script. Contact Tyler Christensen (NOS) for details.

Partial upload of Positional Accuracy fields only.

Partial upload to move data access links to Distribution Info.

LiDAR points were used to produce the deliverables. | Source Geospatial Form: digital data | Type of Source Media: hard drive

Applanix software was used in the post processing of the airborne GPS and inertial data that is critical to the positioning

and orientation of the sensor during all flights. POSPac MMS provides the smoothed best estimate of trajectory (SBET) that is necessary for Optech's post processor to develop the point cloud from the LiDAR missions. The point cloud is the mathematical three dimensional

collection of all returns from all laser pulses as determined from the aerial mission. At this point this data is ready for analysis, classification, and filtering to generate a bare earth surface model in which the above ground features are removed from the data set. The point cloud was manipulated within the Optech software; GeoCue, TerraScan, and TerraModeler software was used for the automated data classification, manual cleanup, and bare earth generation from this data. Project specific macros were used to classify the ground and to remove the side overlap between parallel flight lines.

All data was manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler.

The Baldwin County project (G10PD02126) is immediately adjacent to the NGOM Mobile Bay LiDAR project (G10PD00578). A manual review was performed to ensure that the two datasets tied together as seemlessly as possible. Revisions were made to both the LAS and breakline datasets as needed in order to achieve a smooth transition between the two datasets. NGOM Mobile Bay data was used to produce full tile deliverables on the eastern edge of the Baldwin County West dataset and the western edge of the Baldwin County East dataset. Upon completion of the Baldwin County deliverables, revised copies of the NGOM deliverables that border the Baldwin dataset will be provided in order to ensure that the two datasets agree with each other.

All Class 2 LiDAR data inside of the collected breaklines were then classified to Class 9 using TerraScan macro functionality. A buffer of 1 meter was also used around each hydro flattened feature.

The breakline files were then translated to ESRI Shapefile format using ESRI conversion tools.

Data was then run through additional macros to ensure deliverable classification levels matching LAS ASPRS Classification structure. GeoCue functionality was then used to ensure correct LAS Version. In house software was used as a final QA/QC check to provide LAS Analysis of the delivered tiles.

The NOAA Office for Coastal Management (OCM) received topographic files in LAS format. The files contained lidar elevation and intensity measurements. The data were received in UTM Zone 16 (NAD83) coordinates and were vertically referenced to NAVD88 using the Geoid09 model. The vertical units of the data were meters. OCM performed the following processing for data storage and Digital Coast provisioning purposes:

1. The topographic las files were converted from orthometric (NAVD88) heights to ellipsoidal heights using Geoid09.

2. The topographic las files were horizontally converted from UTM coordinates (m) to NAD83 Geographic coordinates (dd).

3. ASPRS Class 11 (Witheld) was changed to Class 13 (Witheld).

The withheld points were returned to the original class 11 instead of 13 as changes in the Data Access Viewer system allowed flexibility in class schemas.

Georeferencing of files was reset to EPSG 4893 (NAD83(NSRS2007) 3D)