2008 Suwannee River Water Management District (SRWMD) Lidar: Live Oak (FL)

Create custom data files by choosing data area, product type, map projection, file format, datum, etc.

Simple download of data files.

This graphic shows the lidar coverage for the 2008 lidar project covering Live Oak, Florida.

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.

The Secondary Network Stations were used to support the measurement of both LiDAR and OrthoPhoto checkpoint sites. They were set up at 15 kilometer spacing per the 2 centimeter requirements for Secondary Control. Two Secondary Control networks were created due to the geometry of the mapping tiles requirements. The first Secondary Network consisted of 3 secondary stations in the Okaloosa County area. The second Secondary Control network consisted of all remaining mapping areas in the Florida Panhandle. The Secondary Control networks included a total of 80 control points, including 16 recovered NSRS monuments, 2 recovered DNR monuments, and 62 new monuments set for this network.

These GPS ground surveys were executed between May and September 2007. Full details are documented in 3DS's "Final Report of Geodetic Control Survey for LiDAR and Photogrammetry, Northwest Florida," dated March 13, 2008.

The Secondary GPS data was gathered using Trimble & Leica Dual Frequency GPS receivers. Receivers logged data simultaneously in what is commonly referred to as a "static session." A typical session occupation consisted of a minimum of 60 minutes of GPS data with four or more satellites in view, and was documented on an NGS Static GPS Logging Form.

Third Order differential leveling techniques were used to establish elevations on Secondary Network stations in specific areas where published vertical stations could not be occupied

directly with GPS. The leveling measurements were reduced using the 3WIRE.EXE program developed by Dr. Ray Hintz. Curvature and refraction corrections were applied.

The level measurements were adjusted with Least Squares technique using the LEVEL.EXE program developed by Dr. Ray Hintz. All adjustments were referenced to the

NAVD88.

The GPS static measurements were reduced using Trimble Total Control version 2.73 software. Geolab software version 2001.9.20.0 by Microsearch was used for all Least

Squares adjustments. The Secondary Networks were adjusted holding NAD83 values from the Primary Network Adjustment. The final horizontal values were converted to State Plane

Florida North Zone using the U.S. Army Corps of Engineers program CORPSCON version 6.0.1. The vertical values are referenced to the NAVD88. Orthometric heights from the

Primary Network adjustment and additional vertical control stations were held. The NGS GEOID03 (g2003u07.bin) model for the Southeastern United States was used. A centering

error of 3.0 millimeters was used for station setup weighting for all adjustments.

A minimally constrained (free) Least Squares adjustment was run to verify the internal accuracy of the Secondary networks. After evaluating and removing any outliers, a final free adjustment was generated. This final free adjustment consisted of 254 independent vectors. The input error estimates were scaled by a factor of 6.234, which resulted in a properly weighted adjustment with a variance factor of 1.000; there were no flagged residuals. A constrained (fixed) 3-D horizontal adjustment was run using the same input error estimates as were used in the free adjustment; the variance factor was 1.6339 and there were six flagged residuals. A constrained (fixed) 1-D vertical adjustment was run using the same input error estimates as were used in the free adjustment; Station BE3991 was fixed in latitude, longitude and orthometric height; the variance factor was 1.2136 and there were no flagged residuals.

The LiDAR checkpoints were surveyed in groups consisting of the four ground cover categories together with a photo-identifiable point for orthophotography checking. These points were tied to the Secondary Network Stations. These ties were made using Rapid-Static Global Positioning Surveys and conventional level runs where the checkpoints were in close proximity to control points. Conventional surveys were then used to tie the groups together to obtain coordinates and elevation on the remaining points. This is particularly needed for the checkpoints that are located under tree cover.

Each check point site control pair was measured with GPS using static methods from at least two or more geodetic control stations. The remaining checkpoints were measured using conventional surveying methods from the checkpoint site control station pairs. Redundant measurements were made to each check point from two different

setups one on each check point site control station. This minimized the chances of setup, sighting, and rod height blunders from going undetected by allowing independent

comparisons to be made.

The GPS static measurements were reduced using Leica Geo Office Version 5.0 and StarNet Version 6.0 software. StarNet Version 6.0 was also used for the Least

Squares network adjustments. The checkpoint site control stations were adjusted using least squares method. The conventional measurements were reduced by using StarNet Version 6.0. The conventional measurements were constrained to the static GPS horizontal and orthometric heights established on the check point site control stations. The check points

were reduced to NAD83 (HARN). Elevations were reduced to NAVD88. Any significant discrepancies between the conventional measurements and the control

values from the static GPS measurements were investigated and resolved.

PDS interpolated the bare-earth LiDAR DTM to provide the z-value for each of the checkpoints. PDS then computed the associated z-value differences between the interpolated z-value from the LiDAR data and the ground truth survey checkpoints and computed the FVA, CVA and SVA values using procedures in References D and E. The data were analyzed by PDS to assess the accuracy of the data. The review process examined the various accuracy parameters as defined by FDEM guidelines. Also, the overall descriptive statistics of each dataset were computed to assess any trends or anomalies.

The NOAA Office for Coastal Management (OCM) received the files in las format from SRWMD. The files contained lidar elevation and intensity measurements. The data were in State Plane 903, NAVD88 (orthometric) heights in feet. OCM performed the following processing for data storage and Digital Coast provisioning purposes:

1. The data were converted from State Plane coordinates to geographic coordinates.

2. The data were converted from NAVD88 (orthometric) heights in feet to GRS80 (ellipsoid) heights in meters using Geoid 03.

3. The LAS data were sorted by latitude and the headers were updated.

4. Duplicate points and erroneous elevations were removed.