2006 Texas Water Development Board (TWDB) Lidar: Northern Cameron and Willacy Counties

Using a LH Systems ALS50 Light Detection And Ranging (LiDAR) system, standard density (1.4 meter ground sample distance) data were collected over areas in Northern Cameron and Willacy Counties, TX (approximately 1021 square miles). Multiple returns were recorded for each laser pulse along with an intensity value for each return. The data are bare earth classified. The data acquisition occurred in 36 missions between December 14, 2005 and February 23, 2006.

The data was collected by Sanborn Mapping Company, Inc. for the Texas Water Development Board (TWDB) and the Federal Emergency Management Agency (FEMA).

Data arrived at NOAA OCM (formerly CSC) with a number of tiles without classified ground points. This caused issues in the automated delivery of data through the Digital Coast. As a result, users would request ground points (because the data parameters included ground) in areas without this classification. This caused data errors. In order to improve the data use and eradicate errors in automation, a software known as lasground was used to classify unclassified points to ground. The new files were replaced on the internal servers and on the ftp server.

Original contact information:

Contact Name: Ryan Mitchell

Contact Org: Texas Natural Resources Information System (TNRIS)

Phone: 512-463-8337

Email: lidar@tnris.state.tx.us

This LIDAR operation was designed to provide a high density set of masspoints within the defined areas. The data

sets are suitable for the development of contours for use in hydraulic/hydrologic model development, and for assessing

environmental impacts. Typical uses for the data set include: FEMA Flood Plain Map Modernization, DFIRM map updates,

watersheds and other hydro studies per FEMA specifications, county mapping projects, and flood mitigation assessment.

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The Cameron and Willacy Counties data set was received from the Texas Water Development Board (TWDB). It was reviewed by the NOAA Office for Coastal Management at the macro level, which included checking for format and point characteristics for approximately 5% of the tiles. In addition, the entire data set was reviewed to establish that bare earth processing and proper classification of the points had been performed. It did not include accuracy or data processing (e.g. bare earth quality, flightline mismatch, feature removal) assessments. Based on the limited review, the data set on average appeared to be of poor quality.

This determination is based on the issues listed under the reviews below. Again, no accuracy assessment was performed.

The results may be viewed as a formatted document. This document is entitled "Lidar Fact Sheet: Cameron and Willacy Counties" and may be viewed at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/98/supplemental/tx2006_twbd_cameron_willacy_m98_lidarfactsheet.pdf

A footprint for the project acquisition can be viewed here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/98/supplemental/tx2006_twbd_cameron_willacy_m98.kmz

Tile Review

The Cameron and Willacy Counties lidar data do not cover the entire area of Cameron and Willacy, the southern portion of

Cameron County is not covered. The reviewed tiles had some formatting issues; the primary issues noted in this review are:

1. Lack of ground classification (#2) for much of the county. (See Figure 1 of the pdf)

2. Only single returns available

3. Water points remain, not classified

Bare Earth Point Density Review

The general lack of bare-earth classification can be seen in Figure 1 of the pdf. Much of Willacy County and the central

portion of Cameron County have not been classified so the bare earth covers only a portion of the area. This is an important

point-if requesting bare earth points-only a portion of the area will be returned. The barrier island does have ground

classifications, but no water removal.

A footprint of this data set may be viewed in Google Earth at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/98/supplemental/2006_TWDB_Lidar_Cameron_and_Willacy_Counties.kmz

Any conclusions drawn from the analysis of this information are not the responsibility of the

Texas Water Development Board, the Texas Natural Resources Information System (TNRIS), the Sanborn Mapping Company,

the Office for Coastal Management, or its partners.

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer;

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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.

Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.2.2.1350

FEMA LiDAR Specifications; 1 m at 95% confidence level

FEMA LiDAR Specifications; +/- 18.5 cm RMSE in open terrain

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