Merge - MapInfo_Pro_Advanced - 2023

Merge tool

The Merge tool allows multiple rasters to be combined into a single output raster. For overlapping areas, there exist a number of data handling options. All input rasters should have the same projection systems for better result. Even though the Merge tool can merge grids of various coordinate systems, it is recommended to merge grids of the same coordinate system for better performance.

Merge operation can be useful in a telecommunications industry. When a telecommunications company decides to evaluate the line of sight from the transmitters to a receiving antenna. This analysis involves a complete study of the elevation of the area, for example, ground elevation, forestry, height of buildings, and any other vertical obstructions that are liable to block transmissions in the area.

Using the merge tool, you can combine a Digital Elevation Model (DEM) of the area with files containing obstruction data, and use mathematical operators and functions alongwith the required interpolation method to improve the accuracy of the data and analyze the terrain in more detail.

While merging multiple rasters, regions where the rasters overlap each other, a mathematical calculation is performed to determine the new grid value. There are eight calculation methods to merge rasters. All of these calculation methods work with continuous field type. For classified, imagery and image palette field types only Stamp operator is applicable.

Primary grid - The primary grid will have a yellow star beside it. By default, the first raster in the Rasters to Merge list is the primary raster. You can click on the white star beside the input file to make it primary. The primary raster is used to define the geometry and projection of the output file.

Merge Operators

1. Stamp - In stamping, two or more grids are combined, and where they overlap, the values of one of the input grids will overwrite the values of the other. The stamping is controlled by the raster's order in the Rasters to Merge list.
   • The files are processed and stamped into the output file in the order they are presented in the Rasters to Merge list. The first file in the list will get stamped into the output file first, then the second and so on, till the last raster file in the list. For example, in the image below we have 3 input rasters namely, red, green and blue. Observe the stamping with regard to the grid order in the Rasters to Merge list. The blue raster is stamped on top of the others, because according to grid order in the Rasters to Merge list, red having index of "0" is stamped first followed by green and blue.
   • If you change the primary grid in the Rasters to Merge list, it does not affect the stamping order.

   Input File Order

   Stamping in the Output File

   Note: The value of blue would be finally stamped on top of other rasters where they overlap. If you change the primary grid in the Rasters to Merge list, it does not affect the stamping. The primary raster only defines the geometry and projection of the output file.
2. Minimum - If two grids are merged using the minimum calculation, and where the first grid has cells with the value of 50 and the second has cells with the value of 20, the overlapping areas will have cells with a value of 20 in the output grid.
3. Maximum - If two grids are merged using the maximum calculation, and where the first grid has cells with the value of 50 and the second has cells with the value of 20, the overlapping areas will have cells with a value of 50 in the output grid.
4. Average - If two grids are merged using the average calculation, the overlapping areas will have values that represent the average of the cell values of the areas that are overlapped.
5. Sum - If two grids are merged using the sum calculation, and where the first grid has cells with the value of 50 and the second has cells with the value of 20, the overlapping areas will have cells with a value of 70 in the output grid.
6. Median - If three grids are merged using the median calculation, and where all the three input grids have cells with a value of 80, 50, and 30 respectively, the overlapping areas will have cells with a value of the median of the three input grid cell values, which in this case, 50.
7. Average of Min and Max - Using this mode of merging, the overlapping areas of the output grid will have cell values that will represent the average of the minimum and maximum cell values of areas that are overlapped. The Average of Min and Max operator supports only the continuous fields.
8. Count - If multiple rasters are merged, Count indicates the number of valid overlapping cells. For example, if you are merging three raster datasets overlapping one another Count value would be 3 to indicate that all overlapping rasters have valid cells. The Count value would be 2 if any one of the rasters has invalid cells.

Interpolation will be used to resample any differing grid cell sizes to the largest cell size. For information about resampling methods, refer to Resampling methods.

Merge Edit

In case of multiple input files, one of the raster is primary raster. The Edit Primary Raster enables you to merge data from one or more rasters into the primary raster, instead of creating an output raster. The primary raster has a yellow colored star next to it for easy identification.

When the Edit Primary Raster option is selected the output file is not generated. This is useful when you want to see the result even without creating an output file. However, you need to be careful as it will modify your input raster data and can not be reversed.

Multi-Resolution Mode

MapInfo Pro Advanced supports Multi-Resolution tiles when you perform merge operations in the Multi-Resolution Mode. You can create a multi-resolution raster by merging data from different resolution raster files. For example, if you have an elevation data, that is of high resolution in some parts and low resolution in some other parts like countryside, and you want to combine the data in a single raster to perform better analysis of the area. You can select the Multi-Resolution Mode option. It not only saves your disk space but also improves the performance of analysis.

For example, if you have a continuous raster with a resolution of 10 meters and another raster with a resolution of 20 meters, you can merge them to produce a new raster. The Multi-Resolution Mode allows you to decide the resolution of the output tiles of resultant raster.

The MRT output can be enabled by selecting the Multi-Resolution Output check-box and when it is enabled, you can select one of the following options as required:

• Highest Resolution - If you select Highest Resolution, the image decimation is decided based on the minimum cell size of all the overlapping Rasters.
• Lowest Resolution - If you select Lowest Resolution, the image decimation is decided based on the maximum cell size of all the overlapping Rasters.
• Stamp - If you select Stamp, the image decimation is decided based on the current order of input grids listed under the Input File. By default, MapInfo Pro Advanced makes the first file selected as the primary grid, if you add more rasters they are added in sequence under the primary grid. This sequence changes if you change the primary grid and then the image decimation will be decided based on the new order of input grids.

When merging in Multi-Resolution Mode, you need to ensure that the cells in the raster are square, the non-square cells may cause the operation to fail.

Support for MapInfo Virtual Raster

A MapInfo virtual raster is a raster that can be loaded, displayed, and operated upon in MapInfo Pro just like any other raster format. The raster data is acquired or generated on-demand, at run time. The MapInfo Virtual Raster (MVR) is a simple XML file using the .MVR file extension that you can load in MapInfo Pro. As a result, this operation is fast, and you get a preview without generating an actual output Raster file. You see the results instantaneously on a mapper. This option is also available in the Batch mode.