Cartography and Geospatial Technologies Department

Photogrammetry

Although 3-D laser scanning is replacing some photogrammetric applications, photogrammetry continues to be a valuable tool for CRM work. Simple photogrammetric techniques require only minutes longer than regular photography and allow images to be used as quantitative data sources at accuracies equal to time-consuming measured field drawings. More robust photogrammetric methods, such as convergent or stereo photogrammetry, enable true 3-D measurements to be taken, much higher accuracies to be achieved, and even digital elevation models and orthophotographs to be produced. Statistical Research, Inc., uses all three major close-range methods on projects to more quickly and accurately document sites, structures, features, and even artifacts. SRI also employs a balloon for low-level aerial photography and photogrammetric mapping.

Statistical Research, Inc., employed these techniques to document a 9-mile construction corridor along U.S. 60 in Arizona, with particular emphasis placed on several multiacre prehistoric field complexes. In particular, aerial lidar was used to document the ground surface in greater detail than the engineering data while simultaneously obtaining orthophotographs. The aerial lidar was a key component of this nondestructive documentation project. Over the 9-mile-long construction corridor, SRI collected hundreds of millions of X, Y, and Z points. After digitally removing vegetation, Statistical Research, Inc., was able to create a 10-cm contour model—in comparison to a traditional 10-m model—for the entirety of the agricultural fields. Most importantly, for analytical purposes, we have used this model to calculate prehistoric drainage patterns and to quantify the surface area, slope, and aspect of individual field features—things that would be impossible to do otherwise. SRI has used various photogrammetric techniques for Arizona Department of Transportation (ADOT), the Barry M. Goldwater Range (BMGR), the Yuma Proving Ground (YPG), and the Bureau of Reclamation (BOR) in New Mexico.

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