Controlled stereo aerial photography or high density LiDAR data provides the foundation for vector mapping operations. Operators interpret the stereo imagery or LiDAR data on specialized workstations that allow precise 3D measurements. Mapping features such as terrain, structures, roads, hydrology, and vegetation are collected as layers of digital data.
Successful mapping from aerial photography requires photography that is not obstructed by snow, tall grass, leaves on trees or other conditions that impair the accuracy of the mapping. The accuracy of the mapping is directly related to the scale of the photography and to the control.
From the 3D compilation of features a base map is created. Base maps typically include features such as contours, spot elevations, buildings, roads, utilities, hydrology, vegetation, and coordinate grids.
The accuracy of mapping can be described in terms of relative accuracy and absolute accuracy. Relative accuracy refers to the positional accuracy between the various features within the mapping. Absolute accuracy refers to the fit of the map features to their "real world" position. Relative accuracy is determined by the scale of the photography and the method applied to the relative adjustment of the photography or LiDAR data. Absolute accuracy is also determined by those factors and by the distribution and quality of the control data.
Fugro Aerial Mapping is experienced in designing the photogrammetric or LiDAR approach to achieve the accuracy requirements of various vector mapping applications. Project design will establish the control methods and flight planning to ensure the relative and absolute accuracy of each project.