An ArcGIS Map contains references to layers of geographic content and is the foundation for all visual mapping applications in the ArcGIS Maps SDK for Unity. It combines a basemap (for visual context) and data layers (for geographic data).
To build an app with ArcGIS Maps SDK for Unity, you define an ArcGIS Map, a camera (to display geographic data and to navigate around), and environments such as sky and light.
Key concepts
In addition to the basemap and data layers, you also specify the type of ArcGIS Map (global or local), the origin position, and an elevation surface (for topographic context in 3D).
Global scene
A global scene is created using the global map type to display your 2D and 3D content on an ellipsoid.
A global scene is good for when you want to understand or provide context for phenomena that wrap around the ellipsoidal surface of the earth, such as global weather measurements, airline traffic paths, or shipping lanes.
Local scene
A local scene is created using the local map type that projects the terrain and layers on a planar surface rather than on an ellipsoid.
Local scenes can be used for displaying or analyzing data at the local or city scale and are valuable for urban planning and visualizations when you want to view defined areas such as campus facilities or building developments. They can also be used to represent the entire world and have the option of using a fixed extent to clip with rectangular or circular shapes.
Origin position
To place geographic content within a Unity scene, you must specify where the 0, 0, 0 origin coordinate of the game engine space is in the real-world coordinate space. You do this when you create an ArcGIS Map.
When you look at a position that is far away from the origin position, it is recommendable to use the ArcGIS Rebase component for the camera together with the ArcGIS Camera component to work around the 32-bit floating point precision issues. When you look at an area close to the origin position, you do not need to rebase. For more information about rebasing, see ArcGIS Rebase component.
You can specify an origin position anywhere within a spatial reference's coordinate space. See Spatial references for more details about working with spatial references.
Values for Origin position
- X (Longitude) : Specifies the east–west position of a point on the Earth's surface. A projected position value for projected coordinate systems or a longitude value for geographic coordinate systems.
- Y (Latitude) : Specifies the north–south position of a point on the Earth's surface. A projected position value for projected coordinate systems or a latitude value for geographic coordinate systems.
- Z (Altitude) : The vertical distance of the camera above the terrain.
- Spatial Reference WKID : The spatial reference of the X, Y and Z values in Well-Known ID (WKID).
Depending on your app requirements, choose between a global or local scene when you create an ArcGIS Map. Global scenes and local scenes both use layers to display different types of geographic data. The data is typically provided from the basemap layer service and data services.
Camera
Cameras are essential for displaying your game to the player. In ArcGIS Maps SDK for Unity, a camera is used for loading GIS data into your scene.
Elevation
Elevation surfaces add to 3D visualizations by creating relief in your 3D scene. They define height values across the extent of your ArcGIS Map's content, and ArcGIS Map will drape layers on top of the elevation surface.
In most cases, elevation data is read from an elevation service, but can also be read from an map tile package stored locally.
Creating an ArcGIS Map
ArcGIS Map is a container of GIS content and sends information to Unity about what and how it should be rendered.
The Map Creator UI and ArcGIS Map component contain the settings for the Map Type and the Origin position. The spatial reference of an ArcGIS Map created by using the Map Creator UI and ArcGIS Map component is defined by the basemap.
You can manually specify the spatial reference according to the basemap and other layers you are going to add to this container if you use C# API to create an ArcGIS Map. When a spatial reference is specified for the ArcGIS Map, you can add basemap and other layers with the specified spatial reference. When it's not defined, the first layer loaded, typically a basemap, defines the spatial reference of the ArcGIS Map.
To create an ArcGIS Map:
The Map Creator UI contains the settings for Map Type, Origin Position on the Map page.
- Click the Map tab and find the drop-down to select
GlobalorLocal. - In the Origin position, introduce the origin position values and spatial reference WKID.
- Click the Create button.
When there is an ArcGIS Map already created in the scene, the UI pulls the configured values. You can modify the values during the editor mode.
If you select Local, you can configure an extent. For more information about setting up an extent, see local scene.