The LIDAR data sets are immense. For example, the fall 1996 data for South Carolina included 2 million elevation points, and the 1997 data set had 21 million data points. Using techniques such as gridding or clipping can result in a loss of the essence of the data set. Having access to the full data sets makes it possible to extract higher resolution cross-beach profiles and elevation maps.
The National Oceanic and Atmospheric Administration (NOAA) Coastal Services Center has developed an application to visualize the LIDAR data without the need for "thinning" data points. The BeachMapper allows users flexibility to view the data in two different ways: 1) as (approximately) shore-normal profiles across the beach, and 2) as color-coded elevation maps. Profiles can be generated for a single benchmark or for multiple benchmarks. Additionally, users also have the option of entering x,y coordinates. BeachMapper uses Office of Ocean and Coastal Resource Management benchmarks and state plane coordinates as the means for navigating around the state. Data can only be generated in state plane coordinates with this tool.
Note: This is not a geographic information system (GIS) tool - it does not have pan, zoom, or identify capabilities. It was initially written as a simple data visualization tool for South Carolina LIDAR data, and so necessarily was designed for a somewhat limited audience. It is not intended for any serious analysis. Although it has capability to create data files that can be used in GIS and other advanced spatial analysis packages, LDART is a better option for creating large data files (i.e., more than 200,000 data points or somewhere between 5 megabytes and 8 megabytes).![[up arrow]](images/uparrow.gif){kind=small}
Return
to Top of PageFor this example, 1996 and 1997 LIDAR data for the 2810 benchmark, on Folly Island, will be examined.
 |
First, select Folly Island from the drop-down list in the top panel of your main control window. Next, select 1996 from the two dates on the right side of that same panel. To see the location of station 2810, click on the Click here for base map button. In a few seconds, a new window with a map of Folly Island and all the OCRM survey monuments for the island should appear. Minimize or move this window out of the way once you have found station 2810 on the map. The Monument Profile option should already be selected in the middle (gray) panel. The bottom (green) panel has four editable boxes. These boxes give the user control over the endpoints of the axes. If left alone, the program will choose default values for the minimum and maximum values of the x and y axis. Leave the x minimum at 0 for now (it will never be less than 0) but click in the x maximum box and change this value to 400. Change the y minimum in the same way to 0, and the y maximum to 27. Select 2810 from the pull-down benchmark window. Click on the Draw single profile button. A new window with a profile will appear shortly. Leave this window up. |
Go to the BeachMapper window again and change the year to 1997 in the top panel. Click the Draw single profile button again. A profile of the same station with the 1997 data will appear. Notice there is more data in the 1997 plot than in the plot of the 1996 data. You will find this to be the case throughout the data.
Return
to Top of PageThis example will demonstrate how transects can be drawn between survey monuments.
|
Return to the BeachMapper window. Go to the middle (gray) panel, click on the Multiple Profiles button. The bottom panel will now change and turn orange. This panel is similar to the Single Profile panel, except that this panel allows the user to create multiple beach profiles in between survey monuments. Select 2810, the starting monument, from the Draw from drop-down box in the lower left of the panel. The ending monument (2813) will be automatically selected. To choose how many profiles to plot, select a number from 1 to 10 from the Intervals drop-down box. For this example, choose 3. You may change the axis minima and maxima and the swath width just as in the Single Profile window. Change the x axes to 0 and 350 and the y axes to 0 and 20. Click on the Draw Multiple Profiles button. Three new windows should appear, with the window labels indicating the benchmark, and a distance from that benchmark. In this case the benchmark should be 2810, and the three distances should be 322, 643, and 965 feet. The plot at 965 feet should look somewhat like the image at left. |
|
The diagram at left illustrates where these profiles are being drawn. You can see that the total distance between Benchmarks 2810 and 2813 is about 1287 feet. Since you chose to draw three profiles in between these survey monuments, the starting points for the profiles are located on the line drawn between the two monuments, spaced at 322-foot intervals. The data for each profile is then extracted from the starting point seaward. |
Return
to Top of Page
This example will demonstrate how x,y coordinates can be plotted with the BeachMapper Application.
On the middle panel, select x,y Profiles. The bottom panel will change to a forest green and several text boxes will appear. This option is designed for users who already know the starting and ending point coordinates (in State Plane Eastings and Northings) of a desired profile across the data. Fill in the x and y (Easting and Northing) coordinates for the starting and ending points. Sample values are:
Change the y axis values to 0 to 20. Click on the Draw Profile button. The swath width can be changed.
These points should roughly correspond to the ends of a groin at the north end of Folly Island.
Return
to Top of Page
This example will demonstrate how to create a birds-eye, color-coded-by-elevation view of the LIDAR data.
 |
On the middle panel, select Elevation Map. The bottom panel should turn to a beige color. Again, survey monuments are used to navigate through the data. Select Harbor Island from the top panel, and 1997 for the year. View the base map if you wish. In the left drop-down box, monument 1900 should be the default. Leave that as it is. Change the right box to 1960. This map may take a few minutes to draw, so please be patient. When the map is drawn, you will see a depiction of all the LIDAR data points between monuments 1900 and 1960. This is a false color image. That is, the colors represent elevations. Purple is the lowest elevation; it is usually only seen at sea level. Red represents the highest elevation, which will vary depending on what is in the scene. In the image just created, the orange and red colors represent buildings. |
Click on the File
menu option at the top of the window. Choose the Save Data to File option.
You will be prompted to enter a file name in order to save
the data. The resulting file will have State Plane Eastings and Northings
and NGVD-29 elevations, separated by commas. The source data file that BeachMapper
uses to produce these profiles and elevation maps (for the 1997 data) has a size of
330 megabytes, which is the most compact binary format possible. The files you will be creating
here are text files, which take up much more space. Be prepared for a large data
file. This portion of the Harbor Island data returns a 4 megabyte file.
There are two options for viewing the text files in ArcView®. You can use the LIDAR Loader Extension or follow the instructions in the tutorial Loading LIDAR Data into an ArcView Project. Both are located on volume 1 of the South Carolina Coast: A Remote Sensing Perspective CD-ROM. Again be prepared for large data files. Creating ArcView Shapefiles for this portion of the Harbor Island data returns three files totaling about 9 megabytes.
This example shows how a user can extract data for a specific area without having to draw it first.
In the middle panel, select Extract Data. The bottom panel will change to blue. Here all you need to provide are two South Carolina State Plane Northings, and then click the Extract Data button. You will be prompted for an output file name and directory. As before, a comma separated text file will be created. Be prepared for a data set of several megabytes or more.
You may also save data to a file using the File menu option in Making A Color Coded Elevation Map.There are two options for viewing the text files in ArcView. You can use the LIDAR Loader Extension or follow the instructions in the tutorial Using LIDAR Data in an ArcView Project. Both are located on volume 1 of the South Carolina Coast: A Remote Sensing Perspective CD-ROM.
Return
to Top of Page
|
The BeachMapper software application gives you several selections for file output. The transects that were created above can be printed by selecting Print Window from the File menu. Alternatively, transect data can be saved as a comma separated file with distance from the survey monument in the first column and elevation in the second column. To save the data in this manner, select Save Data To File (comma delimited ascii) from the File menu. |
 |
 |
To save image data to a text file, select Save Data To Text File from the File menu on the elevation map. |
Return
to Top of Page
