Arfoundation starts from scratch 8-geospatial API (geospatial) development

ARCore Geospatial API For developers Live View Underlying technology , Including large-scale cloud anchor function , And global visual positioning system （VPS） Access rights of , Can be used to develop multi person shared AR application .

The technology is based on Google Earth 3D Model data and street view image data , The principle is to convert tens of billions of street view images into support VPS Positioning of the 3D Point cloud , A total of trillions of 3D data . In less than a second , According to 3D Location of point cloud data positioning equipment And direction .

Project sample source code ：

https://github.com/sueleeyu/ar-geospatial

One 、 Create project engineering and installation ARCore Extensions software package

See ：

https://blog.csdn.net/weixin_40239288/article/details/125328974

Two 、 Set up google cloud project

Use a visual positioning system （VPS）, You need to associate a Google Cloud project , And in time Google Cloud In the project Enable ARCore API, newly build Google Cloud project ：

1. visit ：https://console.cloud.google.com/projectcreate, New projects .

2. Click create to create a new one ：

3. Select... From the sidebar menu API And the service - library ：

4. Input ARCore API And search for

5. Click Select ARCore API

6. Click enable

7. Enter the following page

3、 ... and 、 Set authorization

After the application needs authorization , To call Geospatial API, Whether the authorization has key authorization and API Key authorization , It is recommended to use keyless authorization .

Realization API Key authorization ：

1. go to Cloud Console Medium  API And the service → The credentials panel , choice Create credentials , Then select from the drop-down menu  API secret key ：

Copy the key after creation ：

Copy the key

2. stay  Unity in , go to  Edit > Project Settings > XR > ARCore Extensions. Android Authentiation Strategy  Drop down menu , choice  API Key

3. stay Android API Key  Field , Paste from Google Cloud Platform To obtain the API secret key , And check the Optional Features  The next two are to be used API Check box ：

Authorization complete . Next, enable Geospatial API.

Four 、 Enable Geospatial API

1.Assets Choose  ARCoreExtensionsConfig  Script object , And then in  Inspector  Window , The drop-down  Geospatial Mode  choice  Enabled.

5、 ... and 、 Write a script

1. mount AREarth Manager, choice Hierarchy-AR Session Origin-Add Component-AR Earth Manager：

2.Hierarchy-‘+’-Create Empty, Name it GeospatialController;Assets-Scripts Right click New GeospatialController.cs, Drag to GeospatialController object ：

To obtain position ：

The main functions are update() To realize ：

1. Judge and check equipment compatibility , call :

EarthManager.IsGeospatialModeSupported(GeospatialMode.Enabled);

Need to return  FeatureSupported.Supported Only then can .

2. Check the tracking status

var earthTrackingState = EarthManager.EarthTrackingState;
Only when the earthTrackingState==rackingState.Tracking when , Geospatial values are valid . As shown below ：

var earthTrackingState = EarthManager.EarthTrackingState;
if (earthTrackingState == TrackingState.Tracking)
{
     // Values obtained by the Geospatial API are valid as long as
     // earthTrackingState is TrackingState.Tracking.
     // Use Geospatial APIs in this block.
}

3. Get camera geospatial pose .REarthManager Manage camera geospatial posture , When TrackingState by Tracking when , request Camera position and direction relative to the earth ：

var earthTrackingState = EarthManager.EarthTrackingState;
if (earthTrackingState == TrackingState.Tracking)
{
  // camera_geospatial_pose contains geodetic location, rotation, and
  // confidences values.
  var cameraGeospatialPose = EarthManager.CameraGeospatialPose;
}

cameraGeospatialPose It contains the information of geospatial posture ：

a. Position in latitude and longitude . Besides , It also provides an estimate of the accuracy of the location information .

b. At an altitude of , And the estimation of altitude .

c. Direction 、 Approximate value of the direction the device is facing , And an estimate of the accuracy of the course .

Place geospatial anchors ：

Use ARAnchorManagerExtensions in ARAnchorManager.AddAnchor establish ARGeospatialAnchor, To anchor the content to the specified geographic coordinates .

When positioning the anchor point relative to the position and direction of the earth , Latitude and longitude are determined by  WGS84 standard Definition , The altitude value is determined by WGS84 The height of the ellipsoid （ In meters ） Definition . Identity rotation takes place with the anchor facing , send X+ Point East ,Y+ Point up , Away from the center of the earth ,Z+ Point south .

private bool PlaceGeospatialAnchor(GeospatialAnchorHistory history)

        {

            Quaternion quaternion =

                Quaternion.AngleAxis(180f - (float)history.Heading, Vector3.up);

            var anchor = AnchorManager.AddAnchor(

                history.Latitude, history.Longitude, history.Altitude, quaternion);

            if (anchor != null)

            {

                GameObject anchorGO = Instantiate(GeospatialPrefab, anchor.transform);

                _anchorObjects.Add(anchorGO);

                return true;

            }

            return false;

        }

Be careful ： It is not supported in the north pole or the South Pole （90 Degree or -90 degree ） Create anchors inside . If you try to use such anchors ,AnchorManager.AddAnchor  Returns the  null.

 Calculate the altitude [Geospatial  file ]：

Getting the altitude at which the anchor is placed is a bit tricky . You must compare the altitude of the equipment location with Geospatial API Compare the altitude of . There are two ways to determine the altitude ：

If the location of the anchor point is close to the user , Please consider using an altitude similar to the altitude of the equipment .

otherwise , Please consider starting from Google Get the altitude value from the height of the map .

Using the camera GeospatialPose The altitude of

You may only need to use from  AREarthManager.CameraGeospatialPose  Obtained altitude , Without cross checking from other sources （ Such as Maps API） The data of , Maybe enough . See above Get the camera geospatial position and direction .

If you can get the position posture in advance by observing the local position by yourself , You can use this data to cross check the  GeospatialPose.

from Google Map the altitude

GeospatialPose  For reporting WGS84 The altitude above the ellipsoid （ In meters ）. Your application needs to  GeospatialPose.Altitude  The value of is compared with the altitude of the equipment location , To determine the exact altitude of the anchor .

You can use  Google Map Get latitude and longitude . Please be sure to close first “ Earth view ”, The method is to navigate to the layer  >  more , Then uncheck the earth view check box in the lower left corner of the screen . This will be enforced 2D visual angle , And eliminate the angle 3D Possible errors caused by view .

After determining latitude and longitude , Please use  Elevation API  according to  EGM96  Specification acquisition height . You must put the Maps API EGM96 Altitude is converted to WGS84, Talent and  GeospatialPose  Compare the altitude . See include both command line and HTML Interface  GeoidEval  Transformation tool .Maps API Use it out of the box WGS84 The specification reports latitude and longitude .

6、 ... and 、UI And interface

1. establish ARView Panel, Click on ‘+’-UI-Panel, Name it ARView,remove component Image and Canvas Renderer

2.ARView Next right click New InfoPanel

Set the properties as follows ：

3.InfoPanel Under the new Text, name InfoText, Set up ：

4.ARView Under the new Panel, name SnackBar, Set up ：

5.SnackBar Under the new Text, name DebugText, Set up ：

6.SnackBar Under the new Text, name SnackBarText, Set up ：

7. SnackBar Under the new Button, name SetAnchorButton, Set up ：

SetAnchorButton-Text：

8. SnackBar Under the new Button, name ClearAllButton, Set up ：

ClearAllButton-Text：

9.Canvas Right click -UI-Panel, name PrivacyPrompt,PrivacyPrompt Next right click New Panel, name FullscreenBackground, Set up ：

10. PrivacyPrompt Next right click New Panel, name PrivacyContent, Set up ：

PrivacyContent Under the new Panel, name PrivacyPromptBackground, Set up ：

PrivacyContent Under the new Panel, name Information Panel, Set up ：

11. Information Panel Under the new Text, name Title Text, Set up ：

Information Panel Under the new Panel, name Text Area, Set up ：

Text Area Under the new Text, name Information Text, Set up ：

Information Text Under the new Button, name URL Button, Delete URL Button Next Text, Set up ：

Start Button Set up click event , call GeospatialController. OnLearnMoreClicked ()：

Information Panel Under the new Button, name Start Button, Set up ：

Start Button Set up click event , call GeospatialController. OnGetStartedClicked()：

7、 ... and 、 Packaging operation

7、 ... and 、 common problem

1. Use ARCore Extension API Example program ：Window-Package Manager-ARCore Extensions-Samples, Click on Import Button to import the sample code to be used .

2. error CS0234： Namespace “UnityEditor” Type or namespace name... Does not exist in “iOS”：

solve ： install UnitySetup-iOS-Support-for-Editor-2020.2.6f1.

8、 ... and 、 reference

1. Unity api：

Unity - Manual: Unity User Manual 2021.3 (LTS)

2. Geospatial file ：

Use ARCore Geospatial API Create a global scale immersive AR Experience  |  Google Developers

3.Google AR：

https://github.com/google-ar

https://github.com/google-ar/arcore-unity-extensions

4. The sample source code of this project ：

https://github.com/sueleeyu/ar-geospatial