iXGIS Map Layers
In iXGIS, a map consists of a series of map layers drawn in a specific order. The layer drawing order determines how data is overlaid and displayed on the map. Upper layers cover lower layers, forming the complete map representation.
A map layer is the display mechanism for geographic data in iXGIS. A layer does not store geographic data itself. Instead, it references a dataset stored in the Cloud Resource Browser and defines how that data is symbolized and labeled in the map view. In other words, a layer is the visual representation of data. It controls color, line style, fill style, opacity, label fields, visible scale range, and related display settings.
Each layer corresponds to a specific geographic dataset, such as streams and lakes, terrain elevation, road networks, administrative boundaries, parcels, building footprints, utility pipelines, or orthophotos. Layers can reference multiple data formats, including Shapefile, PostGIS tables, GeoPackage, raster data, and imagery. These datasets are stored and managed in the iXGIS Cloud Resource Browser.
When you add data to a map, select a dataset from the Cloud Resource Browser and create a layer from it. iXGIS automatically applies a default drawing style to the new layer so the data can be displayed immediately. For clearer and more professional map production results, adjust the symbol system and label properties after creating the layer, such as classified symbols, graduated rendering, field-based label rules, and visible scale ranges.
iXGIS also supports AI-assisted symbolization. Based on field meanings and data characteristics, the system can intelligently recommend suitable color schemes and symbol representations to help you design maps more efficiently and improve map readability.
Map Layers
In a map, geographic datasets are displayed as layers. Each layer represents a specific dataset overlaid on the map. Map layers can communicate information through:
- Discrete feature classes, such as collections of points, lines, and polygons
- Continuous surfaces, such as elevation or other raster surfaces
- Satellite imagery that covers the map extent
Common examples of map layers include streams and lakes, terrain, roads, administrative boundaries, parcels, building footprints, utility lines, and orthophotos.
In addition to representing geographic information, the symbols, colors, and labels of each layer help describe the objects on the map. By interacting with layers, you can query features and view their attributes, run analysis operations, edit features, and add new features to datasets.
Layers do not store the actual geographic data. Instead, they reference datasets such as feature classes, imagery, and rasters. Referencing data this way allows layers in the map to automatically display information from the underlying GIS data.
To set properties for a map layer in iXGIS, such as map symbols and label rules, click the layer menu in the layer list, then select Style or Labels.
Contents List
The contents list shows all layers on the map and indicates what the features in each layer represent. Each layer has three controls on the right:
- The zoom icon zooms to the current layer.
- The eye icon controls layer visibility.
- The menu icon opens the layer menu.
The order of layers in the contents list determines the drawing order in the map, from bottom to top.
Scale-Based Visibility
Scale-based visibility defines the map scale range in which a layer is visible. This helps ensure that datasets suitable for one scale range are hidden until the map is viewed at an appropriate scale. It also lets you define layer display rules for different map scale ranges, which is useful when building multiscale maps. In iXGIS, this is controlled by minimum and maximum zoom levels.
Symbols
Symbols are graphic elements used in map display. Common symbol types include:
- Markers, mainly used to display point locations
- Line symbols, used to display linear features and boundaries
- Fill symbols, used to fill polygon features
Labels
Labels are text strings used to label features in map layers. Attributes can be used to define the field that provides label text and to control how labels are drawn on the map. Labels are dynamic. They are recalculated each time the map is redrawn, such as when you pan or zoom the map.
Layer Groups
Layer groups contain other layers. They help organize related layers in a map. Layer groups can also be used in multiscale maps by grouping layers that correspond to specific map scale ranges. Each layer group can define scale-based drawing rules.
Layer group menu:
- Add Data
- New Layer Group
- Remove: Remove the layer from the iXGIS project.
- Rename: Rename the data.
- Zoom to Layer: Zoom the iXGIS map to the full extent of the layer.
- Move Up: Move the layer up one level.
- Move Down: Move the layer down one level.
- Move to Top: Move the layer to the top.
- Move to Bottom: Move the layer to the bottom.
- Visible Levels: Control the display levels of the layer, from level 1 to level 28.
In addition to using the menu, you can drag layers to move them into or out of a layer group.
Layer Menu
Vector and raster layers have similar layer menus.
- Remove: Remove the layer from the iXGIS project.
- Rename: Rename the data.
- Zoom to Layer: Zoom the iXGIS map to the full extent of the layer.
- Open Attribute Table (vector only): Open the attribute table of vector data.
- Move Up: Move the layer up one level.
- Move Down: Move the layer down one level.
- Move to Top: Move the layer to the top.
- Move to Bottom: Move the layer to the bottom.
- Label Symbols: Symbolize vector data or raster data.
- Set Labels (vector only): Configure labels for vector data.
- Visible Levels: Control the display levels of the layer, from level 1 to level 28.
- Export Features / Export Raster: Export the vector data or raster data again.
- Properties: View the data properties.
Online map layers have a separate layer menu.
- Remove: Remove the layer from the iXGIS project.
- Rename: Rename the data.
- Move Up: Move the layer up one level.
- Move Down: Move the layer down one level.
- Move to Top: Move the layer to the top.
- Move to Bottom: Move the layer to the bottom.
Table layers have a separate layer menu.
- Open: Open the table.
- Remove: Remove the layer from the iXGIS project.
- Display XY Data: Create vector data from the table as the data source.
Layer Types
Layers have different types. Some layers represent specific types of geographic features, while other layers represent specific data types. Each layer type has its own mechanism for displaying and symbolizing layer content, as well as specific operations that can be performed on that content.
Common layer types include:
- Feature layer: A layer that references a set of feature data, or vector data, representing geographic entities such as points, lines, and polygons. The data source of a feature layer can be a geodatabase feature class, Shapefile, PostGIS table, or GeoPackage.
- Raster layer: A layer that references a raster or image as its data source.
- Table layer: A table layer that displays only an attribute table.
- Online map layer: A layer that lets users directly access and load map services from the internet in iXGIS, including WMS services, WMTS services, and other web services. Examples include Tianditu maps and Tianditu imagery. By integrating online map services, iXGIS users can easily bring global geographic information resources into their own map projects.
Layer Properties
Layers have many properties that can be viewed and configured. To view layer properties, click Properties in the menu of a layer.
General
Displays the name and path of the layer data, for example:
- Data name: China major rivers - polygon vector.shp
- File path: China administrative boundaries/China major rivers - polygon vector.shp
Vector Information (Vector Data)
Displays attribute information for vector data.
| Property | Value | Description |
|---|---|---|
| Source | PostgreSQL | The data is stored in a PostgreSQL database. |
| Geometry Type | Line | The table stores linear features (LineString / MultiLineString), suitable for roads, rivers, pipelines, and similar features. |
| Feature Count | 210 | There are 210 geometry records, meaning 210 features in total. |
| Has Z | No | The geometry uses 2D coordinates (X and Y) and has no height or elevation dimension. |
| Has M | No | The geometry has no measure value (M), an additional dimension commonly used for linear referencing. |
Raster Information (Raster Data)
Displays property information for raster data.
| Property | Example value | Description |
|---|---|---|
| Rows | 5999 | Number of cells in the Y direction. Rows x columns equals the total number of cells. |
| Columns | 6000 | Number of cells in the X direction. |
| Band Count | 1 | The raster has one band, indicating a single-band raster such as elevation or classification results. |
| Pixel Size X | 0.000833333 | Horizontal resolution, in the units of the coordinate system. Here it equals 3 arc seconds divided by 360, approximately 92 to 93 meters depending on latitude. |
| Pixel Size Y | 0.000833333 | Vertical resolution. Matching X and Y values indicate square cells. |
| Format | GTiff | GeoTIFF format, a common format that supports spatial reference information. |
| Source Type | GISMETA_RASTER | Data source or internal system identifier indicating raster data. |
| Pixel Type | Signed integer | Each cell is represented by a signed integer, suitable for elevation values, classification codes, and similar data. |
| Bit Depth | 16 | Each cell uses 16 bits. The signed 16-bit integer range is usually -32768 to 32767. |
| NoData Value | -32767 | A cell value that represents no data and is excluded during analysis or rendering. |
| Color Table | Missing | The raster has no built-in color table, so custom rendering is required for display. |
| Pyramids | Yes | Pyramid layers have been built to speed up display at different zoom levels. |
| Pyramid Levels | 4 | Four pyramid levels were generated by progressively downsampling from the original resolution. |
| Pyramid Resampling | NEAREST | Nearest-neighbor resampling is used, usually for classified or integer rasters to avoid averaging values. |
| Compression | Missing | TIFF compression is not specified or the file is uncompressed, so the file may be large. |
Extent
Displays the bounding extent of the layer. Values use the units of the current data coordinate system. For a geographic coordinate system, the unit is degrees. For a projected coordinate system, the unit is usually meters or kilometers.
Spatial Reference
Displays the spatial reference of the data. Geographic coordinate systems and projected coordinate systems use different parameters.
Geographic coordinate system parameters:
| Property | Value | Description |
|---|---|---|
| Name | WGS 84 | The most widely used geographic coordinate system in the world. EPSG:4326 is its common code. |
| Datum | World Geodetic System 1984 ensemble | Defines the Earth reference frame on which the coordinate system is based. WGS 84 is commonly used by GPS. |
| Ellipsoid | WGS 84 | Indicates which ellipsoid is used to approximate the shape of the Earth. |
| Semi-major Axis | 6,378,137 | Equatorial radius of the ellipsoid, in meters. |
| Semi-minor Axis | 6,356,752.314245179 | Polar radius of the ellipsoid, in meters. |
| Inverse Flattening | 298.257223563 | Describes how flattened the ellipsoid is. Flattening = (a - b) / a; this value is its reciprocal and is the standard WGS 84 value. |
| Prime Meridian | Greenwich | Longitude 0 degrees passes through the Greenwich prime meridian in the United Kingdom. |
| Angular Unit | degree | Coordinates are expressed in degrees. Both longitude and latitude use degrees. |
Projected coordinate system parameters:
| Property | Value | Description |
|---|---|---|
| Coordinate System Name | WGS 84 / UTM zone 49N | A UTM zone 49N coordinate system based on WGS 84, suitable for areas around 108 degrees E to 114 degrees E with a central meridian of 111 degrees E. |
| Projection Method | Transverse Mercator | The standard projection method used by UTM. |
| Authority / Code | EPSG:32649 | The official EPSG code. 326 indicates WGS 84 northern hemisphere UTM zones, and 49 indicates zone 49. |
| Latitude of Origin | 0 | The projection origin latitude is the equator. This is the UTM default. |
| Central Meridian | 111 | The central meridian is 111 degrees E, corresponding to UTM zone 49. |
| Scale Factor at Origin | 0.9996 | The fixed UTM scale factor used to reduce projection distortion. |
| False Easting | 500000 | Adds 500,000 m in the east direction so coordinates within the zone are positive. |
| False Northing | 0 | In the northern hemisphere this value is 0. In the southern hemisphere it is usually 10,000,000 m. |
| Linear Unit | metre | Coordinate unit is meters. |
Statistics (Raster Data)
Provides statistics for each raster band, including the minimum value, maximum value, mean, and standard deviation.
Map Layer Operations
Add Data
There are several ways to add map layers. To create a new map layer, add a dataset to the map. You can add datasets in the following ways:
- Use the Add Data button in the project menu.
- Use the Add Data button on the Start tab.
- Select data in the Cloud Resource Browser, then use the Load button.
- Drag a layer from the Cloud Resource Browser directly into the map view or layer manager.
Adjust Order
When a new layer is added, it is automatically placed above other layers of the same type. For example, a new line feature layer is placed above other line feature layers. Therefore, you may need to position layers appropriately. For example, layers that form the map background, such as terrain layers, are usually placed at or near the bottom of the contents list.
iXGIS provides two ways to reorder layers: drag layers with the mouse, or use the layer menu commands Move Up, Move Down, Move to Top, and Move to Bottom.
Remove Layers
If a layer is no longer needed in the map, you can remove it. Select the layer, open the layer menu, and click Remove.
Removing a layer does not affect the underlying data source on which the layer is based.
To permanently delete data, use the Cloud Resource Browser.
Symbolize Layers
iXGIS provides many layer display options for representing geographic information. Layers can be represented with symbols, colors, and labels in multiple ways. To learn how to symbolize and render layers, continue reading Symbols and Styles (Vector) and Symbols and Styles (Raster).