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ENVI

Automatically Create Tie Points

Automatically Create Tie Points

  1. From the Tie point method drop-down list, select one of the following options:
    • ENVI Standard - Area based: See Step 3 under Creating Tie Points for instructions for automatically selecting seed points.
    • AGATE - Area based: AGATE is an automatic tie point tool that often finds more tie points than the ENVI standard automatic tie point tool. AGATE is optimized to utilize all system resources and requires that the input image be georeferenced.The area-based method is similar to ENVI’s standard automatic tie point tool; it compares image subsets to find tie points.
    • AGATE - Frequency based: This method transforms image subsets into frequency space using Fast Fourier Transforms, maximizes correlation, then creates tie points.
  2. From the Tiling method drop-down list, select a method for reprojecting image tiles when doing comparisons. When sensor model information is available, reprojecting image tiles according to the DEM helps improve tie point accuracy.
    • Reproject tiles w/out DEM: Reproject image tiles without the use of a digital elevation model (DEM).
    • Reproject tiles w/ DEM: Using a DEM in rugged areas can dramatically improve the quality of tie points. If you select this option, you are prompted to select a DEM when you click Next.
  3. The Num Processors parameter is automatically set to the number of processors available on your system. To reserve one or more processors (if more than one is available) for other activities while AGATE is running, reduce this setting.
  4. Click Next to proceed to the next step.



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