Getting LIDAR Data

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One of the challenges of using LIDAR data is the size of the data sets. For a 200 mile stretch of beach, there can be more than 74 million elevation measurements, which would require 852 megabytes to store it. As of the publication of this CD-ROM there are over one billion elevation measurements stored on-line, requiring 14 gigabytes. To allow easy access to this data set, the NOAA Coastal Services Center has created the LIDAR DAta Retrieval Tool, or LDART

Using LDART

Choosing Your Area of Interest

The first part of LDART is a MapObjects® Internet mapping application that allows you to choose your area of interest. This application will allow you to zoom in, zoom out, and pan (move around) on the maps for all the states where data have been collected. Once the area of data to be downloaded has been selected, click the Select Data Parameters button to go to the next screen.

Selecting Projection, Datum, and File Format

The second part of LDART is a Java® applet that allows the selection of the data parameters needed to merge LIDAR with other data sets or maps.

Most state agencies are required to use a particular projection and is frequently one of the state plane projections. LDART can project one's data to any of the coastal state plane zones.
The vertical datum to which the LIDAR data are referenced is not a "sea level" datum, which means that the elevations of the water are usually not close to zero. There are several generally accepted vertical datums, two of which are currently supported within LDART: the National Geodetic Vertical Datum of 1929 (NGVD 29), and the North American Vertical Datum of 1988 (NAVD 88). Choosing between datums usually depends on other data sets, which may refer to a particular datum. If there are no other data sets, then NAVD 88 is recommended, as it is a more accurate system. Refer to the list of frequently asked questions for help with this topic.
There are currently two output file format options available within LDART. One format is a simple text file, with the x, y and z values separated by commas. The other format is a binary file that is easily imported into ArcView® or most image processing software packages.
More datums and output options are planned for LDART in the near future. Check the LDART site for current options.

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Getting to LDART

Follow this link to get to LDART.

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