What is SADI?

The image above is an example of 3D SADI and is best viewed with red/green glasses.

The SADI Process

SADI (Scale-Accurate-Digital-Imaging) is created from standard 9"x9" aerial photograph stereo pairs which have been scanned at a resolution of 2000 dpi. The imagery is generally obtained by the use of standard fixed wing aircraft, and as such does not have the attendant higher mobilization and demobilization costs typical with helicopters.

Westwood/ETG computes and applies an Aerial Triangulation (AT) solution to the digital stereo pairs resulting in a photogrammetric model from which we can collect XYZ (northing, easting, elevation) DTM data in the form of mass points and break lines. We can also collect and code visible features such as overhead conductors, poles, curbs, and manholes, etc.

This data can be exported to numerous commercially available engineering and GIS programs for additional base map preparation. Depending on the altitude at which the photography was obtained, a screen resolution on the order of 0.1 ft/pixel or less is typical but it can be at even higher resolutions with the use of a helicopter. Our deliverable includes a scalable image which is accurate across the entire line of flight and typically several miles in width.

2D & 3D Viewing 

The SADI product is an accurate digital orthographic image viewable in either 2D or 3D on a computer monitor. Zoom in to observe the details of planimetric features and measure distances in 3D, across the aerial map as well as vertically, anywhere on the image.

SADI Uses

• Export digital orthographic imagery as a reference file to CAD programs such as AutoCAD and Microstation, and GIS programs such as ArcInfo and Mapinfo, and overlay vector data.
• Import aerial survey DTM data into line design programs such as PLS-CAD or TLCAD.
• With XYZ coordinates for any photo-identifiable point, measure distances and obtain bearings from public rights-of-way to points lacking direct access.
• Study corridor and access route alternatives.
• Create plan/profiles for design.
• Create contours anywhere in the image.
• Export data to support clearing and road cut/fill calculations.
• Evaluate encroachments.
• Plot well locations and sensitive areas such as waterways, wetlands, mines, and unstable slopes.

SADI Summary

SADI has a wide functional range and is not limited to traditional design. Our clients use our aerial survey data for route planning studies, environmental support, right-of-way records, and operations and maintenance functions.

We supply highly accurate and scalable geo-referenced aerial-based photo imagery and Digital Terrain Model (DTM) data. Our offerings are unique within the mapping industry.