Orthorectify a single satellite scene

The tools and capabilities in the ortho mapping suite allow you to create an orthomosaic from a collection of satellite images. You can also orthorectify a single satellite scene using the tools in the Ortho Mapping wizard. To accomplish this, you need the following data:

  • Rational polynomial coefficients (RPC)—This is typically imbedded in the image file or included as a separate metadata file.
  • Digital elevation model (DEM)—The input elevation data is used to orthorectify the imagery during block adjustment. The global DEM is used by default, but it is recommended that you use a local DEM for your project area.

    • If you operate in an environment without easy access to the internet, have low bandwidth, or want to use a higher-quality global DEM, you can also download an enhanced Global DTM of the Earth for use in your ortho mapping projects.
    • The local DEM or DEM layer used must have EGM96 or WGS84 Vertical Coordinate System (VCS). Use the Project Raster tool to reproject your DEM if it has a VCS that is different than EGM96 or WGS84.

  • Ground control points (GCPs) or a reference image.

Create an ortho mapping workspace

You can create a satellite imagery workspace for your project using the workflow wizard.

  1. On the Imagery tab, click New Workspace.
  2. On the Workspace Configuration page, type a name for the workspace.
  3. Click the Workspace Type drop-down arrow and choose Ortho Mapping.
  4. For Sensor Data Type, click the drop-down arrow and select Satellite.
  5. Accept all other defaults, and click Next.
  6. On the Image Collection page, choose the Sensor Type for the satellite data you are adding to the workspace.
  7. For the Folder Containing Images, click the browse button, navigate to the folder containing the image, select it, then click OK.
  8. The supported Workspace Spatial Reference information will be auto-populated. If the system is unable to auto-determine the appropriate spatial referencing, manual entry of this information is also supported. Manually entering the spatial referencing information for the workspace can be done by doing the following:
    1. Under Spatial Reference, click the Browse button, and set the Current XY and Current Z coordinates for the project.

      When processing satellite imagery using Ortho mapping, a local planimetric (XY) coordinate system is supported. The Vertical Coordinate System (VCS) needs to be EGM96 (WKID 5773) or WGS84 (WKID 115700).

  9. Click Next.
  10. In the Data Loader Options window, for Elevation Source, use the Browse button and choose a DEM, which will be used to orthorectify the satellite scene. You can also specify a Z Factor value and a Z Offset value. Check the check box to apply a geoid correction.
    1. Under Geoid Correction, if your local DEM has ellipsoidal height, select None from the drop-down list. If your DEM has orthometric height, ensure EGM96 is selected.

      Most elevation data uses orthometric heights, so you must apply a geoid correction. If the units and base of the elevation are different from the satellite imagery, you must set a Z Factor value and a Z Offset value, respectively.

    2. Click the drop-down arrow and choose the appropriate Processing Template for your workspace.

      The processing template determines the type of data you want to process, such as single-band, multiple-band, or pan-sharpened images. The available templates depend on the Sensor Type value that was chosen.

      If the dataset being processed is already pansharpened, choose the Multispectral processing template. Select the Pansharpened template only when you have both panchromatic and multispectral imagery.

    3. Expand the Advanced Options section to expose additional settings.
    4. Check the Estimate Statistics check box to estimate the image statistics for your output workspace.

      Calculate the statistics if you want to use a contrast stretch to display your imagery.

    5. Optionally, edit the Band Combination parameters to reorder the band combination from the default order.
    6. For the Pre-processing options, choose either Calculate Statistics or Build Pyramids before you create your workspace.
  11. Click Finish to create the workspace.

When the ortho mapping workspace is created, the satellite scene is loaded in the workspace and displayed on the map.

Add GCPs to your ortho mapping workspace

GCPs are points with known x,y,z ground coordinates, often obtained from ground survey, and used to ensure that the photogrammetric process has reference points on the ground. GCPs can be imported from survey data using the Import GCPs tool, or computed using a reference image with the Compute GCPs tool. You can measure GCP and create tie points in the GCP Manager pane. For more information about how to add GCPs, see Add GCPs to your ortho mapping workspace.

Add tie points

After the GCPs are imported or computed, select the Manage GCPs tool from the Manage GCPs menu to open the GCP Manager pane, which allows you to add the tie points for your GCPs. In photogrammetry, this process is known as creating a measured tie point or a tie point that corresponds to a GCP in an image. For more information about how to add tie points for corresponding GCPs, see Add GCPs to your ortho mapping workspace.

Adjust and orthorectify the satellite scene

After GCPs and tie points have been computed, the next step is to perform block adjustment using the tools in the Adjust and Refine groups. The block adjustment uses the tie points and the input DEM to orthorectify your satellite scene.

  1. On the Ortho Mapping tab, in the Adjust group, click Adjust Adjust.

    For more information about adjustment options, see Adjustment options for ortho mapping satellite imagery.

  2. After the adjustment is complete, select Multiple Products in the Product group.

    The Product Generation Settings page allows you to specify the ortho mapping products you want to create.

  3. Uncheck the box next to Digital Surface Model (DSM) and Digital Terrain Model (DTM).
  4. Ensure the Orthomosaic check box is checked.
  5. Below Orthomosaic, ensure the Generate Orthomosaic option is selected.
  6. Verify that the Select Mosaic Candidate, Color Balance and Generate Seamlines options are unchecked.
  7. Click Next.
  8. In the Orthorectification Settings window, under Elevation Source, select the DEM that will be used to orthorectify the satellite scene.
  9. Click Next.
  10. In the Orthomosaic Settings window, select the settings for the output image.
  11. Click Finish to orthorectify the single satellite scene.

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