Feature Selection

In iXGIS, you can select features in a layer in several ways depending on your workflow:

Select by Feature

Click a feature directly on the map to select it.

Select by Graphics

Draw a graphic on the layer to select features that intersect that graphic. Supported shapes include rectangle, polygon, lasso, circle, and line.

Select by Attributes

Use visual SQL condition queries to filter target features precisely.

Parameters:

• Input layer: Select the layer to filter from the drop-down list.

• Selection type: Specify how the selection result is handled. The following types are supported:

  • New selection: Replace the current selection with the generated selection. If there is no current selection, create one directly.
  • Add to current selection: Add the generated selection to the existing selection.
  • Remove from current selection: Remove features that meet this query condition from the current selection.
  • Select subset from current selection: Further filter the selected features to keep only the subset that meets the condition.

• Input SQL query condition:

  • Field: The name of the data column to query.
  • Operator: A symbol that performs an operation or logical test, such as equal to, not equal to, or greater than.
  • Value: The specific data to compare with the field.
    tip

    Values in SQL query conditions can also use fields, which enables relationship operations between fields.

• Multiple SQL statements: Attribute queries support combining multiple SQL statements.

  • Multiple conditions in one statement: Connect conditions with AND or OR. For example, station_id is not equal to 25369 AND province is equal to Jiangxi Province selects all stations in Jiangxi Province except station 25369.
  • Multiple-statement combination: For example, select stations in Jiangxi Province, exclude station 25369, and filter stations with rainfall less than 5000.

• Invert Where clause: When selected, the SQL query uses the NOT operator to exclude records that meet the condition.

Select by Location

Select features from one or more target layers based on their spatial relationship to features in a source layer. Multiple layers can be selected at the same time. For example: select weather stations located within a specified area.

Parameters:

• Target layers: One or more layers on which to perform the selection.

• Spatial relationship: Defines the spatial rule between source layer features and target layer features.

  Understand source and target first

  • Source layer: The reference layer used as the spatial condition, such as administrative polygons, road lines, or protected area polygons.
  • Target layer: The layer from which features are selected, such as business points, parcel polygons, or river lines.

  You can think of it as using the source layer as a filter to find features in the target layer that meet the spatial relationship.

  Spatial relationships:

  Spatial relationship	Meaning	Typical scenario	Notes
  Intersect	The two features touch or overlap in any way, including boundary contact, partial overlap, or complete coverage. A distance of 0 is usually considered intersecting.	Select parcels that intersect a river; select roads that pass through a planning area.	This is the most common and broadest relationship. If you need features completely inside an area, do not use Intersect.
  Within a distance	The minimum Euclidean distance from the target feature to the source feature is less than or equal to the search distance. This is similar to creating a planar buffer around the source.	Find business points within 100 m of roads; find villages within 500 m of a river.	Units depend on the coordinate system. Projected coordinate systems usually use meters. If a geographic coordinate system uses degrees, Euclidean distance is not recommended.
  Within a geodesic distance	The minimum geodesic distance from the target feature to the source feature is less than or equal to the search distance, accounting for the curvature of the Earth.	Filter by distance in longitude and latitude data; perform distance analysis across regions.	Suitable for geographic coordinate systems. Compared with Euclidean distance, differences are more obvious over large areas or at high latitudes.
  Contains	The target feature contains the source feature. Boundary contact is allowed.	Find a management polygon that covers a road; find a parcel polygon that contains a point.	Points or lines on the boundary are also considered contained. Use Completely contains if boundary contact must be excluded.
  Completely contains	The target feature strictly contains the source feature. Boundary contact is not allowed.	Select only facility points completely inside a protected area, excluding points on the boundary.	Features may be excluded because of boundary contact. If the result is unexpectedly small, try Contains first.
  Within	The target feature is within the source feature. Boundary contact is allowed.	Select business points within an administrative area; select parcels inside a planning area.	This is the reverse direction of Contains: here, the target is inside the source.
  Completely within	The target feature is strictly within the source feature. Boundary contact is not allowed.	Select only features completely inside a polygon, excluding features that touch the boundary.	Like Completely contains, boundary contact causes exclusion.
  Identical to other features	The two features have exactly the same geometry and coincide.	Remove duplicates; verify whether two datasets are consistent.	Very sensitive to coordinate precision. Even small offsets can make features non-identical.
  Boundary touches	Only the boundaries touch, and interiors do not overlap, such as adjacent parcels.	Find parcels adjacent to a parcel; find administrative areas that share a boundary.	If there is area overlap, use an Intersect or overlap-type relationship instead of Boundary touches.
  Share a line segment with other features	The two features overlap along a boundary or line segment, sharing part or all of an edge or line.	Find polygons with shared boundaries; find overlapping road centerline segments.	Suitable for checking boundary consistency or duplicate lines.
  Crossed by the outline	Boundaries cross, commonly when a line crosses a polygon boundary or polygon boundaries intersect each other.	Find roads that cross a planning area boundary; check polygon boundaries for crossing errors.	This is more related to boundary or topology checks and is not the same as Within or Contains.
  Center within feature extent	The geometric center, centroid, or center point of the target feature falls within the source feature.	Summarize features by the area containing their centroid, such as assigning parcels to administrative areas.	For long, narrow, or concave features, the centroid may be counterintuitive. Do not use it as a replacement for Intersect or Within.

  Choosing a reliable relationship

  • If any touch or overlap should count, use Intersect.
  • If features should be inside a polygon including its boundary, use Within. If they must be strictly inside without touching the boundary, use Completely within.
  • For distance-based selection, use geodesic distance first for longitude and latitude data. For projected coordinate systems over small areas, Euclidean distance is usually acceptable.

• Invert spatial relationship: When selected, chooses features that do not satisfy the spatial relationship above.

• Source layer: The feature layer used as the spatial reference.

• Search distance: Specifies the buffer value for spatial relationships such as within a distance.

• Selection method: Like attribute selection, supports new selection, add, remove, subset, and switch current selection (invert selection).

Feature Operations

After selecting features, common follow-up operations include setting the highlight style, viewing feature attributes, exporting selected features, and copying and pasting features to other layers.

Export Features

Export Features lets you output selected features or an entire layer from the map as a new independent data source. You can export features in either of the following ways:

Method 1:

Step 1: In the project management panel, open the options menu for the layer whose features you want to export.

Step 2: Select Export Features.

Set the required parameters to export the features.

Method 2:

Step 1: In the project management panel, open the options menu for the layer whose features you want to export.

Step 2: Select Open Attribute Table.

Step 3: Go to Table on the top toolbar.

Step 4: Select Export Features on the tab bar.

Set the required parameters to export the features.

Copy and Paste Features

Features selected by graphics, attributes, or location can be copied and then pasted, or pasted to another layer.

Set the Highlight Style for Selected Features

Step 1: Go to Start on the top toolbar.

Step 2: Click the diagonal down-right launcher button on the tab bar.

Step 3: In user options, open the selection settings.

Settings include:

• Point size/color: Sets the display size and color of selected point features.

• Line width/color: Sets the display size and color of selected point outlines, line features, and polygon boundaries.

• Fill color: Sets the fill color of selected polygon features.

• Transform sketch color: Sets the color of the selection box when a feature is selected.

• Selection mode: Controls how drawn graphics hit features.

  Method 1: Partially within. A feature is selected when the selection box intersects it.

  Method 2: Completely within. A feature is selected only when the selection box completely contains it.