What's the difference between a digital terrain model (DTM) and a scalable terrain model (STM) ?
A DTM is an InRoads native file type for what is now superseded by a Terrain element in OpenRoads. It is a surface represented by triangles. A scalable terrain model (STM) is a Descartes native file type (also available in OpenRoads Designer) that supports very large datasets and supports multi resolution display such that as you zoom out less triangles will display on screen since you don’t need high detail for viewing and then more detail will display as you zoom in. STMs support high resolution image draping. STMs can display contours on the fly without adding new elements to the DGN. STMs cannot be used as a target for corridor modelling. STM will eventually be superseded by the newer Scalable Mesh 3SM. For example here is a scalable mesh of New York https://m.youtube.com/watch?v=oFP_TYDzVB8
Thank you for your reply.
In fact, we have made a pointcloud and a 3mx file based on aerial pictures taken by an RTK drone with ContextCapture. The site was heavily planted. A DTM was created with the pointcloud and an STM with the 3mx file.
The two models are différents. The DTM is above the different trees while the STM is under them, but we don't know nor why nor how. And it's seems that the levels under the trees are not at the real ground level ...
Hi Bernard,
Without seeing the data and confirming the workflow used it would be hard to confirm the reason for the difference but I would guess that the image capture did not provide sufficient overlap to accurately determine the ground level or perhaps the trees obscured too much ground for it to be captured. This could be followed up with technical support if you log a service request at connect.bentley.com
Regards
Paul