Get Depth from detected face using Vision and ARKit iOS

Question

I am trying to achieve something like this using Vision and ARKit, so my idea is to get landmark points from Vision and deploy node using those points. I am using this demo as a reference. To date, I have been able to find the landmark points of the face using Vision. Now to use those points in ARKit to add nodes to the scene. I am unable to get the depth, which is essential for the node's position.

After searching SO, I found this post to convert CGPoint to SCNVector3, but here I am having an issue as I don't having any reference plane which is can use to get depth by hit testing against.

So, how can I get the perfect depth using CGPoints, other than using hitTest, or is there any other way I can achieve those result shown in video.

Here is the code which is implemented

            CGPoint faceRectCenter = (CGPoint){
            CGRectGetMidX(faceRect),CGRectGetMidY(faceRect)

        }; // faceRect is detected face bounding box

        __block NSMutableArray<ARHitTestResult* >* testResults = [NSMutableArray new];

        void(^hitTest)(void) = ^{


            NSArray<ARHitTestResult* >* hitTestResults = [self.sceneView hitTest:faceRectCenter types:ARHitTestResultTypeFeaturePoint];
            if(hitTestResults.count > 0){
                //get the first
                ARHitTestResult* firstResult = nil;
                for (ARHitTestResult* result in hitTestResults) {
                    if (result.distance > 0.10) {
                        firstResult = result;
                        [testResults addObject:firstResult];
                        break;
                    }
                }
            }
        };

        for(int i=0; i<3; i++){
            hitTest();
        }

        if(testResults.count > 0){
            NSLog(@"%@", testResults);
            SCNVector3 postion = averagePostion([testResults copy]);
             NSLog(@"<%.1f,%.1f,%.1f>",postion.x,postion.y,postion.z);

            __block SCNNode* textNode = [ARTextNode nodeWithText:name Position:postion];
            SCNVector3 plane = [self.sceneView projectPoint:textNode.position];
            float projectedDepth = plane.z;
            NSLog(@"projectedDepth: %f",projectedDepth);


            dispatch_async(dispatch_get_main_queue(), ^{
                [self.sceneView.scene.rootNode addChildNode:textNode];
                [textNode show];
            });
        }
        else{
           // NSLog(@"HitTest invalid");
        }
    }

Any help will be great!!