Combining multiple types of geospatial data collection, such as aerial photogrammetry and mobile lidar, requires a detailed knowledge of sensors, error models, navigation, ground control and data processing. This would be a challenge for any geomatics firm, but the rewards can be a rich data set that can have multiple uses and provide a high return on investment.
As the video below demonstrates Continental Mapping, based in Sun Prairie, WI has developed a set of best practices for combining aerial photogrammetric data with mobile lidar. This hybrid approach addresses and overcomes a number of weaknesses that are inherent with each method.
For example, aerial photogrammetry is not going to produce the engineering grade, hard surface accuracy that mobile lidar is capable of for a highway project, but it will provide a wider swath than a mobile lidar system which is limited by the height of the sensor above the pavement. If the highway has steep embankments the mobile lidar will have difficulty recording the topography. Aerial photography will not capture the underside of overpasses and bridges, nor provide street level imagery as a mobile lidar system will.
The key for bringing the data sets together is the ground control. As pointed out in the video, by using the same ground control stations for both the aerial and the mobile data collections the two data sets will be in the same coordinate system, but each system will still have their own error model that will need to be addressed.
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