What is SADI?

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

The SADI Process

SADI 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.

ETG then 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 then subsequently be exported to numerous commercially available engineering and GIS programs for additional base map preparation (see Westwood’s Survey & Mapping Services). 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 real magic of our product is that you will see an accurate digital orthographic image in either 2D or 3D directly on your computer monitor. You can easily 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

In addition, with our model, you are also able to:

• Export digital orthographic imagery as a reference file to CAD programs such as AutoCAD and Microstation, and GIS programs such as ArcInfo and Mapinfo, at which point you can 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 of which you may not have 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

ETG’s aerial mapping product has a wide functional range within an organization and is not limited to only 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. Principally, we provide two services, Scale-Accurate Digital Imagery (SADI) and "enhanced" Scale-Accurate Digital Imagery (eSADI) which enables the photogrammetric map to be viewed in 3D.

eSADI

An enhanced Scale-Accurate Digital Image (eSADI) depicts a geo-referenced composite 2D/3D corridor or block area. eSADI is ETG’s software viewer that enables the photogrammetric map, or eSADI image, to be viewed in 3D. Entire project areas can be viewed using eSADI. The software has neither hardware locks nor licensing restrictions. Vector data can be readily imported, overlaid on the image, and selectively displayed. Image resolution, scale factor, XYZ coordinates, and latitude and longitude are continuously displayed as the cursor moves around the image.

With eSADI we can also quickly develop a mosaic model of a corridor or block area by using open source data. We, however, will format the data for eSADI and create a 2D/3D model on which you can readily measure distances, add feature vector data, create contours, and cut profiles. Since there are no flights for photography required if open source data is used, this represents a very fast and cost effective method of studying alternatives for transmission line routes, pipeline routes, transportation corridors, waterways, and other types of projects.