Horizontal and Vertical Control for Aerial Mapping

1. Definition

An aerial mapping ground control survey is a combination of that reconnaissance, field data collection, analyzation, computation and documentation necessary to provide the horizontal and vertical position of specific ground points to be used in setting the scale of aerial photographs and determining the relative position of elements visible in the photographs. Standards and specifications used for aerial mapping ground control are the same as ground control for right of way mapping and design surveys and are described TxDOT’s GPS Manual, Chapter 2 of the TxDOT Survey Guide, and the TSPS Manual of Practice for Categories 7 and 8, Horizontal and Vertical Control Surveys. TxDOT uses aerial photography extensively to capture information on existing conditions for project development. The Aerial Photography Section of the Information Systems Division has established specifications for the various types of panels and placement of those panels throughout the project limits. The general layout of the panels and spacing between the panels can be found in Chapter 2, Sections 4 and 5 of the TxDOT Survey Guide and must be adhered to explicitly if TxDOT is to capture enough redundant ground control data to perform checks to insure the quality and accuracy of the aerial mapping for detailed design. Center panels which require coordinate and elevation locative values are generally placed along the flight centerline at between 800’ and 1800’ and wing panels which require elevation locative values are generally placed left and right of the center panels at between 200’ and 600’. The proposed panel layout should be reviewed and approved by the photogrammetrist and the designated TxDOT representative before paneling work begins.

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Horizontal and Vertical Control for Aerial Mapping Task Sequence and Quality Control Measures