Post processing of tree height through reference measuring mechanism

For the upcoming specifications on urban tree inventory tracking each tree should be able to be individually processed for its tree height. The online tool https://eleif.net/photo_measure.html can be taken as example. Images ready for the post processing will have to display a reference height stick already used in many tree monitoring activities.
https://d2nbfg2zjsirqs.cloudfront.net/1584086120353.jpg is a good example of the red stick 1.5 meter length used for height calculation.