To input data into newly created fields within an attribute table, the table must first be open by selecting “Attribute Table” from the context menu of the vector layer.
Values or text can be entered by double-clicking on a specific cell. To apply the same value or formula to one or more rows, the user must select the desired rows (highlighted in blue), then right-click on the relevant column (for example, “Type”). A contextual menu will appear, from which the option “Calculate Field” should be selected. This opens the “Calculate Field” dialog box.
In this dialog box, the “Input Table” must be selected, and the “Field Name” chosen, which corresponds to the column to be edited. It is also possible to manually type the field name. By default, the “Expression Type” is set to “Python”, but it can be changed to “Arcade” or “VBScript” as needed.
Under “Expression > Fields”, all the fields of the input table are listed. If values already exist in some cells and should be replicated in others, the “Insert Values” box allows the user to assign those values to selected cells. This requires selecting the appropriate field in the “Expression > Fields” list.
To input a specific value into a field (such as “Type”), the value must be inserted after the equal sign. If the value is numeric, it is typed directly. If it is text, it must be enclosed in quotation marks. For example, to label selected rows as “Housing”, the expression would be: Type = "Housing". This process may be repeated with other values such as “Church”, “Hospital”, “Police”, or “School”.
Entering information in the attribute table with the “Calculate” tool.
As a practical exercise, new fields should be added to each vector layer (shapefile) previously created. Each field must be configured according to the following specifications:
Structure for creating fields in tables.
The following information should be entered into the new fields:
- For control_points: enter “P1” or “P2” in the “Name” field, depending on the location in the georeferenced image.
- For road_network: enter the following values in the “Type” field: “Main way” for segments near X: 691790 Y: 9532578, “Unpaved way” for segments near X: 691394 Y: 9532401, “Path” for segments near X: 691570 Y: 9532693 and X: 691261 Y: 9532773, “Route” for segments near X: 691991 Y: 9532450 and X: 692028 Y: 9532861, “Street” for all remaining urban area segments. To locate a specific coordinate on the map, the “Go to XY” button located in the “Map > Navigate” tab should be used.
- For water_network: enter “Malacatos River” in the “Name” field for the main river.
- For plant_cover: use the georeferenced image to assign “Grassland”, “Crops”, or “Forest” to the “Type” field, depending on the land cover.
- For lake: assign “Santa Anilla Lake” to the “Name” field.
After completing the digitization of all layers, the raster image (“image.png”) can be deactivated or removed from the “Contents” panel by right-clicking on it.