Exploring the Viewshed Dialog Box - MapInfo_Pro_Advanced - 2023

Input File

Select a raster file on which you want to calculate the viewshed for a single or multiple points.

Select Fields, Bands

The viewshed feature only works on continuous field types. Only one band can be selected for viewshed analysis. If the input grid file has more than one continuous field or there are multiple bands in the available continuous field, the field band selector drop-down appears. Select any single band from this drop-down list.

Viewshed Options

The Viewshed Options section consists of the following:

• Viewshed Mode - Choose whether you want to calculates the viewshed from a single point or multiple points on the raster. The Viewshed Mode drop-down list consists of the following options:
  1. Single Point - Using this option, you can calculate the viewshed from a single point on the grid. Type the X and Y position of the viewshed origin, and apply the other parameters.
  2. Multiple Points (.TAB) - Using this option, you can import multiple viewshed origins which is specified using a MapInfo TAB file containing point locations.

Single Point viewshed mode calculates the viewshed using a single point TAB file on the raster. You can set the following options for Single Point viewshed analysis.

You can set the following options for Multiple Points (.TAB) viewshed analysis.

Click More Options to set the following:

• Use Sweep Azimuth - Select or clear this check-box if you want the sweep angle and azimuth to be calculated for each tower or viewshed origin.
• Sweep Azimuth - The sweep azimuth defines the center direction line of the horizontal angle to the scan. The value is defined clockwise in degrees from 0 to 360 with 0 degrees oriented towards north. You can either specify the azimuth angle of each viewshed point from a column in the TAB file or enter a constant value for all points.
• Sweep Angle - The sweep angle defines the horizontal angle limits either side of the sweep azimuth to restrict the scan. The sweep angle is applied either side of the sweep azimuth. For example, if you wan to perform a scan over a total horizontal radius of 30 degrees you should specify a sweep angle of 15. You can either specify the sweep angle of each point from a column in the TAB file or enter a constant value for all points.
• Smooth - Select or clear this check-box if you want to eliminate small irregularities in the input grid. When Smooth is selected the Compute Intervisibility option will not appear.
• Filter Width - Denotes the kernel size of to be used for Gaussian smoothing. Must be an odd number.
• Use Complex Calculations - If you select this option, MapInfo Pro Advanced will calculate the value by which the height of the target point should be raised or lowered to make the point visible from the viewing point (source). This option is available for Single Point only.
• Value Classification - Classifies the line of sight values for the viewshed output.
• Null cells outside viewshed radii - If selected, all cells outside the viewshed radius are assigned null values.
• Clip to viewshed radii bounds - Clips the viewshed area.
• Create classified raster - Saves the output viewshed file as a classified raster file.
• Compute Intervisibility - Select this option if you want to compute intervisibility in the viewing radius while processing multiple towers. Calculating the intervisibility between two points requires finding the straight line between the points, finding elevations along the profile to determine any obstacle in the line-of-sight.

  When checked, the system computes intervisibility and returns the number of points falling in a direct line of sight. Intervisibility plays a major role in terrain analysis, therefore, this feature is useful in determining how many towers are visible from a point in the viewing radius. This option will not appear if Smooth is selected.

Output File

Specify a name, location and format for the output raster that you are creating. In the Output File box enter the name you want to specify for your output file. Click to browse to the location in your computer to save the output file. You can also select the required output file format.

Click Output Settings to specify the following. The values in Output Settings are controlled by the Raster Preferences dialog; however, you can override those settings here.

• Display Output File - Select the check-box, if you want to open the output file in the Map window on completion of the operation. You can configure to make this the default behavior from the Raster Preferences dialog.

  If the output file format is an MRR or a TIFF, additional options appear. The available options are listed below.

• Compression Settings
  • Data Balanced
  • Data Speed
  • Data Space
  • Advanced

  The Data Balanced option allows you to achieve a balance between speed of operation and file size. The system selects the best combination of speed and space for you. With the other two options Data Speed and Data Space, you can choose between speed of operation and storage space. Choose Advanced option to set the advanced compression settings such as compression method, level, and encoding type. For details on the Advanced option, see Compression Settings.

• Compression- Select a suitable compression method and level for the data. For more information on compression, see Compression methods.
• Encoding Type - Select a suitable Encoding Type for the data from the list. It enables you to compress the data when saving a raster to MRR format. Encoding Type is enabled only when the raster field type is Continuous and the compression method is lossless such as ZIP, LZMA or LZ4. The drop-down list contains the following:
  • None - No encoding.
  • Previous Column Linear - Performs linear estimation of the value from previous two columns.
  • Previous Column Value - Predicts the value from previous column.
  For more information, see Encoding Type.