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Merging Layers in GIS: How to merge layers with SGIS Desktop?

The ability to merge layers opens a world of possibilities for synthesizing data, discovering relationships, and gaining a comprehensive understanding of our spatial environment. But what exactly does it mean to merge layers in GIS, and how can this process elevate our analytical capabilities?

Understand the Essence of Merging Layers

At its core, merging layers in GIS involves the combination of multiple individual layers into a single, consolidated layer. This process allows us to create a cohesive dataset by merging the geometries, attributes, and symbology of different layers. By harmonizing diverse sources of spatial information, we transcend the limitations of individual layers, creating a more comprehensive and powerful resource for analysis and decision-making.

The act of merging layers is a transformative step that enables the synthesis of information, unearthing hidden relationships, and revealing patterns that may not be apparent in isolated layers. By merging layers, we can explore how different geographic features interact, identify correlations between attributes, and gain a holistic view of complex spatial phenomena.

Streamlining Data Management

Merging layers in GIS also streamlines data management processes by reducing redundancy and enhancing efficiency. Instead of working with multiple separate layers, merging allows us to consolidate similar data into a single layer, simplifying the dataset and making it more manageable. This consolidation not only saves storage space but also facilitates data updates, editing, and maintenance.

Are you eager to learn how to combine layers in GIS?

Let’s review this step-by-step guide on how to merge layers in SGIS Desktop.

Step 1: Prepare the Layers

Begin by gathering the layers you wish to merge. Ensure that the layers share a common spatial reference system. Usually, there are some pre-established requirements to be met in order to proceed with the merging procedure:

  1. The main Layers List panel should contain more than one layer. This is pretty clear, you need to have at least two layers available for merging.
  2. The layers can only be merged if they have the same geometry type. This means that you cannot merge layers that have different types of geometry, such as merging points with polylines, points with polygons, or polylines with polygons.
  3. Usually, in many other softwares, there is a requirement that in order to merge two layers, those layers need to have compatible attribute tables. While this is certainly desirable, there may be scenarios where that is not the case. If you do not check that requirement box, SGIS will give you three options to choose from. Those options include ‘Same Field’ matching, ‘Matched Fields’ matching and ‘Union Fields’ matching. Each of them will be thoroughly explained.

If needed, perform any necessary data cleanup, such as removing duplicates or correcting errors, to ensure data integrity before the merge.

Step 2: Open the GIS Software

Launch SGIS Desktop software.

Step 3: Load the Layers

Import the layers you want to merge into your GIS software. Use the “Add Layer” function to load each layer into the project workspace.

Step 4: Initiate the Merge Process

Locate the tool in the ‘Layer’ menu from the main toolbar. This tool allows layer merging within SGIS software. Access this functionality to initiate the merge process.

When you open the Merge Layers function, a new form will be displayed. The central part of the form features a list displaying all the layers, referred to as the All Layers list.

It is recommended that you check the layer that you want to use as the reference layer for the merging process. This reference layer will serve as the focal point for comparing and merging with other layers.

Step 5: Define the Merge Parameters and your desired output

Configure the merging parameters based on your requirements. SGIS Desktop uses three different methods which we’ll explain right now. Our merging procedure consists of three parts, specifically for the attributes of the layers being merged. These parts include:

Same Fields

Matched Fields

Union Fields

The “Same Fields” type of merging involves merging layers that have the same structure of attribute fields. To select layers with the same attribute field structure, follow these steps:

  • Check the reference layer that has the desired attribute field structure.
  • Click on the “Control” button. This will initiate the process of identifying and selecting layers that have the same attribute field structure as the reference layer.
  • After the “Control” procedure, all layers that share the same attribute field structure as the reference layer will appear as checked in the list of layers.

These checked layers represent the ones that can be merged together.

The “Matched Fields” type of merging involves merging layers based on matching fields in the attribute table. In this case, only the fields that match the fields of the reference layer will be merged, while the other fields will be dismissed. To perform a “Matched Fields” merge, follow these steps:

  • Check the reference layer that contains the desired fields for merging.
  • Click on the “Control” button. This will initiate the process of identifying and selecting layers with matching fields to the reference layer.
  • After the “Control” procedure, all layers with matching fields to the reference layer will appear as checked in the list of layers. These checked layers represent the ones that can be merged together based on their matching fields.

During the merging process, only the common fields among the selected layers will be merged, while the non-matching fields will be disregarded. This allows for a more focused and targeted merging of layers, ensuring that only relevant attribute data is combined.

The “Union Fields” type of merging involves creating a merge where all fields from all layers will be retained and displayed in the attribute table.

If you have a checked layer within the list of selected layers and you want to view or preview the structure of the attribute fields for that layer, you can click on the Fields View button. This action will display the result in the Selected Layer Fields section.

Clicking on the “Fields View” button will provide you with information about the attribute fields of the selected layer. You can use this feature to examine the field names, data types, and other properties associated with each attribute field in the layer. By viewing the attribute field structure, you can gain insights into the available data within the layer and make informed decisions regarding the merging process.

Step 6: Execute the Merge

To initiate the merging procedure, you need to click on the Apply button. Once clicked, a dialog will prompt you to enter the name for the newly created layer resulting from the merging process. After providing the name, the merging operation will be performed, and the newly merged layer will be displayed in the main Layers List panel.

Step 7: Review the Merged Layer

By simply clicking on the Close button, you can close the Merge Layers form. This action will remove the form from the screen, allowing you to continue with other tasks or operations within SGIS Desktop.

Once the merge process is complete, review the resulting merged layer. Ensure that the geometries, attributes, and symbology have been combined accurately.

Step 8: Save the Merged Layer

Last but not least, Save the merged layer as a new file to preserve the integrity of the original layers. This will allow you to retain the individual layers for future reference while working with the consolidated dataset.