Geometric function

The Geometric process produces an orthorectified image based on a sensor definition and a terrain model.

To learn about orthorectification, see Fundamentals of orthorectifying a raster dataset.

The inputs for this function are the following:

• Input Raster
• Constant Z
• DEM

You can use this function when your raster data has rational polynomial coefficients. If you don't have a digital elevation model (DEM), you can specify the Constant Z value, but this would generate an inaccurate result; even a low-resolution DEM tends to have better accuracy than a Constant Z value. If you have a DEM, check the Use DEM check box.

When using a DEM

You can use a DEM contained within the mosaic dataset, or one stored in a raster catalog, as a raster dataset or as a mosaic dataset whose output is a DEM.

Z Factor

Satellite rational polynomial coefficients (RPCs) are scaled for elevation datasets with vertical units in meters. If your elevation uses other vertical units, enter a Z Factor to rescale to meters. For example, if your elevation units are in feet, you would use a value of 0.3048 to convert your elevation units from feet to meters.

Z Offset

The base value to be added to the elevation value in the DEM. This could be used to offset elevation values that do not start at sea level.

Geoid

Most elevation datasets, such as USGS NED, or ArcGIS Online World elevation, are orthometric heights, so it is necessary to select the Geoid correction for compatibility with satellite RPCs which require ellipsoidal heights. Check the Geoid check box to apply the geoid (EGM96) correction to the z-values, unless your DEM is already referenced to ellipsoidal heights.

Validating the geodata transformation

If you click the Geodata Transform button, a window appears displaying the information specific to the geometric transformation that will be applied to the raster data.