Generate a DSM using ArcGIS Reality for ArcGIS Pro

Available with Standard or Advanced license.

Available for an ArcGIS organization with the ArcGIS Reality license.

A digital surface model (DSM) is a digital elevation dataset of the earth, including the elevation of objects on the ground surface such as trees and buildings. DSMs can be derived from stereo image pairs using photogrammetric methodologies. A stereo pair is comprised of two overlapping images of the same geolocation taken from different perspectives. The stereo image pairs of an image collection are used to generate a point cloud (3D points) from which elevation data can be derived. Stereo image pairs are also used to support stereoscopic image analysis, 3D feature compilation, and mapping applications. Typical image overlap to produce point clouds is 80 percent forward overlap along a flight line, and 60 percent overlap between flight lines, so that every location on the ground is covered by multiple images.

The derived elevation data can be used in a various applications including orthorectifying the image collection in the Reality mapping workspace. The recommended image type for generating a DSM is nadir imagery.

To generate a DSM using the ArcGIS Reality for ArcGIS Pro DSM wizard, complete the steps below.

Note:

• Before you begin the workflow, ensure that you have created a Reality mapping workspace and completed the block adjustment process.
• DSM generation is recommended using nadir imagery.
• The minimum number of images required to generate a DSM or DSM mesh product is two overlapping images. Product quality is increased using more overlapping images.
• When processing satellite imagery in Reality mapping to produce a DSM or a DSM mesh product, the planimetric (x,y) coordinate system must be defined using the WGS84 UTM reference frame, and the vertical coordinate system (VCS) must be WGS84 (ellipsoid).
• When processing satellite imagery in Reality mapping to produce a DSM or a DSM mesh product, product boundary, water body, and correction features must be in the WGS84 UTM reference frame, and the VCS must be WGS84 (ellipsoid).

1. On the Reality Mapping tab, click the DSM button in the Product group.

   The Reality Mapping Products Wizard window appears.

2. Click Shared Advanced Settings.

   The Advanced Product Settings dialog box appears, where you can define parameters that will impact the Reality mapping products that will be generated. For a detailed description of the advanced product settings options, see Shared Advanced Settings in the wizard.

   

The Quality and Scenario Type settings are automatically set by the application and should not be changed to ensure optimum performance and product quality. However, if you want to generate a reduced resolution product, the Quality setting can be lowered. See Shared Advanced Settings in the wizard for more information about the impact of various quality settings on product generation.
3. To manually set the DSM output resolution, for Pixel Size, select Meters from the drop-down menu, and provide the required pixel size.
4. For Product Boundary, select a feature class identifying the output product extent from the drop-down list or click the Browse button and browse to and select one.

   It is recommended that you provide a project boundary for the following reasons:

   • Define the proper output extent—When you do not define a product boundary, the application automatically defines an extent based on various dataset parameters that may not match the project extent.
   • Reduce processing time—If the required product extent is smaller than the image collection extent, defining a product boundary reduces the processing duration and automatically clips the output to the boundary extent.

5. To specify a water body feature layer, click the Browse button next to Waterbody Features.

   Note:

   If water body features, such as lakes and rivers, exist within the project area, it is recommended that you add a precreated 3D feature class identifying those areas, using the Waterbody Features setting to hydrologically enforce those features in the output product. Use the stereoscopic compilation in ArcGIS Image Analyst to generate the 3D feature layer that identifies water body features. This ensures that there will be no image stretching around hydrological feature boundaries in the output due to differences in elevation between the derived DSM height and the feature class height values.

   The Waterbody Features options are Precise and Coarse. Use the Precise option when the 3D polygon being added accurately defines the shape of the hydrological features in the project area. Precise polygons can be created using the stereoscopic compilation in ArcGIS Image Analyst. A precise water body polygon can also be derived from national mapping organizations with open data policies. Additionally, it can be created using 2D heads-up digitizing from an authoritative, orthorectified imagery that is temporally similar, with the aid of a DEM.

   Use the Coarse option when a generalized 3D polygon is being used as the water body feature. Generalized polygons can be created using a 2D heads-up digitizing workflow. If 2D heads-up digitizing is used to create a precise or coarse polygon, it must be converted to 3D (x,y,z) before it can be used as a water body feature. See Introduction to 2D and 3D features for additional information about converting a 2D feature to 3D. When using a coarse water body feature, the shape of the polygon must follow the shape of the water body feature for best results.

6. For Processing Folder click the browse button , browse to disk, and define the Reality mapping temporary folder location.

   The temporary files required for generating 2D or 3D products will be stored here.

7. Accept all other default values and click OK.

   The Advanced Product Settings dialog box closes, and you are returned to the Products Generation Settings page in the Reality Mapping Products wizard.

8. In the Products Generation Settings window, click Next to go to the DSM Settings page.
9. For Output Type, select either Tiled or Mosaic from the drop-down list.
   • Tiled—Generate system-defined square tiled image subsets.
   • Mosaic—Generate a single image covering the project area.
10. Choose a Format option for the output.
    • Cloud Raster Format—Generate a packaged multilayered file, which is ideal for cloud storage.
    • TIFF Format—Generate output in standard GeoTIFF format.

      The default output format for tiled True Ortho products is TIFF.

11. For Compression, choose one of the following:
    • None—No compression is applied to the output product. This is the default option.
    • LERC—Limited Error Raster Compression (LERC) is a controlled lossy compression algorithm. The rate of compression is controlled by a tolerance setting. For example, setting a tolerance of 0.001 results in a DSM value that was previously 15.654321 to be scaled to 15.654.
12. Optionally, set a value for NoData Value that’s appropriate for the output data bit depth.
13. Click Finish to initiate product processing.

    When processing is complete, the DSM product is added to the following locations:

    • Reality Mapping container in the DEMs folder in the Catalog pane
    • Contents pane, Data Products category, and the 2D map view