GIS software uses two basic types of data:
- Spatial Data — containing the coordinates and identifying information describing the map itself
- Attribute Data — containing information that can be linked to the spatial data—for example, pipe diameters or manhole invert and rim elevations in the spatial data.
Spatial data contain the coordinates and identifying information for various map features. Three types of features can be represented on the Map View:
The various physical aspects of the GIS map—watershed boundaries, rivers, sewer pipes, manholes, and so forth—are organized into layers according to their common features.
For example, the collection of points that represent stormwater manholes can be organized into a manhole layer, the collection of polylines that represent stormwater sewer pipes can be organized into a Stormwater Pipes layer, and the collection of polygons that represent watershed basins can be organized into a Watersheds layer.
A layer can be either static or thematic. Static layers use the same graphical attributes (color, line width, and so forth) for all features in a layer. Thematic layers can use different graphical attributes to classify the features in the layer. For example, a thematic polygon layer representing watersheds could use different colors to show the composite curve number of each watershed. A thematic polyline layer representing stormwater pipes could use different line widths and/or colors to differentiate pipe diameters.
The second type of data used in a GIS is attribute data. With GIS software, data views can be associated with the Map View through links to the spatial data. For instance, the spatial data might represent a water distribution pipe network and contain information for each pipe when it was installed, last inspected, pipe material (i.e., cast iron, PVC, etc.), pressure rating, roughness coefficient, and so forth.
The Data Explorer panel is used to view the attribute data of a geometric element in a river model. Simply select the desired model element (HEC-RAS, AutoCAD, GIS, etc.) from the Map View, and the software will automatically display the corresponding attribute data in the Data Explorer panel.
The user can adjust the Data Explorer panel’s height by dragging the top of the panel splitter bar up (or down) to see more information about the selected element. Additionally, the user can edit the attribute data of the selected element (described below). Note that the selected geometric element must be a GIS entity and its corresponding GIS data layer must be unlocked. Additionally, the GIS data layer must be the active layer in the Drawing layer dropdown combo box on the Map Data Layers panel.
The Data Explorer contains two columns: the attribute fields (Field Name) of the selected geometric element and the corresponding attribute values (Field Value).
If the selected geometric element’s layer is locked, then the attribute fields will be read-only and will appear green.
Editing Attribute Data
The following methods can be used to edit the GIS attribute data:
- To modify an attribute value for a selected GIS entity, click on the GIS entity in the Map View and make your changes in the attribute value column.
- To modify attribute values for all entities in a layer at the same time, click on one of the GIS entities in the Map View and then right click and choose Select Similar from the displayed context menu. Then, make your changes in the attribute value column.
- To modify attribute values for just a few entities in a layer, multi-select all of the entities in the Map View of the same layer that you want to update. Then, make your changes in the attribute value column.
Saving GIS Attribute Data Changes
When the project is saved, the software will update the corresponding GIS geodatabase file.