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What is LiDAR Technology


Quiz Questions

1.What is LiDAR?
LiDAR has become an established method for collecting very dense and accurate elevation data across landscapes, shallow-water areas, and project sites
LiDAR is a method for photogrammetry
2. This active remote sensing technique is similar to radar but uses
laser light pulses
radio waves.
3.These collection techniques are popular within the surveying and engineering communities because they are capable of producing extremely high accuracies and point densities, thus permitting the development of precise, realistic, three-dimensional representations of railroads, roadways, bridges, buildings, breakwaters, and other shoreline structures.
True
False
4.Which one of the followings are the advantages of LiDAR for data collection over most other techniques?
higher resolutions
centimeter accuracies
ground detection in forested terrain
All of the above
5.LiDAR _____________to see under trees, when acquiring elevation data using remote sensing data collected from above the Earth’s surface (e.g., airplanes or satellites).
Does not have the ability
Does have the ability
6.The combination of an airborne platform and a scanning lidar sensor is an effective and efficient technique for collecting elevation data across
tens to thousands of square miles
ten to thousand acres
7.The most common and cost-effective platforms for acquiring lidar data over broad, continuous areas is
Airplane and helicopter
Cars
Boats
8. Most airborne platforms can cover about ________ square kilometers per hour and still produce data that meet or exceed the requirements of applications that demand high-accuracy data. Airborne platforms are also ideal
50
100
1000
9.Airborne platforms are also ideal for collecting bathymetric data in relatively clear, shallow water. Combined topographic and bathymetric lidar systems on airborne platforms are used to map shoreline and nearshore areas.
True
False
10.Among the chief capabilities of Lidar is the ability to map discrete changes at a very high resolution over a large area very quickly. Which one of the following could be used for such an application?
Updating and Creating Flood Insurance Rate Maps (Figure 2-6)
Forest and Tree Studies
Coastal Change Mapping
All of the above
11.Lidar points color capability can represent different attributes of the data. (Figure 2-3)
True
False
12.Lidar data represent several important improvements over previous and commonly used vertical data sets generated for U.S. Geological Survey (USGS) topographic quad maps. The data available through the National Elevation Dataset (NED) have largely been created using photogrammetric techniques. The resulting accuracy of the NED is on the order of 3 meters or 10 feet (Gesch, 2007) with 10-to 30-meter resolution. Photogrammetric elevation generation is a time-consuming, labor-intensive process, especially for high-accuracy products, and therefore is a data set that is not updated often. Moreover, the ability to map areas hidden by or below trees is limited because the technique inherently requires that a location be visible from two vantage points (i.e., two images). The result is that much of the NED are fairly old, have vertical accuracies that limit coastal applications, and have horizontal resolutions that preclude the definition of coastal features. Lidar, while _____________ photogrammetry, is a more rapid technique that relies largely on new technology to produce results. Note that the NED is being updated with lidar data as they become available, particularly for the newer 1/9th arc-second (about 3 meters) resolution NED, but as of 2011 only 28% of the U.S. excluding Alaska had lidar coverage.
Similar in cost to
More expensive than
13.Certain user or customer specifications can help maximize the data for specific applications. Lidar data, like most remote sensing information, can be highly customized to satisfy a certain use. The downside, however, ________that there can be a host of “options” to wade through, both in use and in purchasing.
Is
Is not
14.The highly automated aspect of lidar collection lends itself to rapid deployment and data capture. Temporal resolution is also important for tide-controlled lidar collections. The ability ________during all hours of the day makes mission planning significantly easier than for photogrammetric techniques.
To fly
Not to fly
15.The results of an analysis can vary when using the same base data if different processing techniques are used; this is both an advantage and a disadvantage to the use of lidar data. This variance stems from the massive amount of data and the need to resample or group them (i.e., grid them). On the positive side,
a significant amount of data can be removed to get only the information sought; on the negative side, the techniques used to sample the data will or could vary and create incompatible results.
The technique might be faster, but more expensive.