Five-minute GIS _ tilt photography single technology

After the second issue of "Five Minutes GIS | Tilt Photography Technology", I believe everyone has a preliminary understanding of tilt photography technology. This issue will explain in depth the single technology of oblique photography.

Source of monomer technology

In the second project, we learned that no matter which modeling scheme is adopted, the final oblique photography model can be regarded as a continuous TIN triangulation with high-resolution images on the surface. This continuous TIN triangulation not only brings us a more realistic tilt model, but also brings us an inevitable problem-in GIS management and application, if we can't select and query the tilt photography model separately, we can only view it as a base map like an image, and can't apply it further, resulting in a single tilt photography technology.

What is a monomer?

"Monomer" actually refers to every object that we want to manage separately, which is an individual entity object that can be selected and separated, endowed with attributes, queried and counted. Only with the ability of "personalization" can data be managed, not just for viewing. In most GIS applications, it is the most basic functional requirement to select buildings and other ground objects, endow them with attributes, and query and analyze them. Therefore, singleness has become a difficult problem that must be solved in the application of oblique photography model in GIS. At present, there are three widely used monomer methods: cutting monomer, ID monomer and dynamic monomer.

Cutting monomer

The idea of cutting monomer is as follows:

ID monomer

ID singularity means that by combining the existing two-dimensional vector surface data, the ID value of the corresponding vector surface is assigned to each vertex of the triangulation as an attribute, so that the same ID value is stored in the vertices of the triangulation corresponding to the same object. When the mouse selects a triangular patch, other triangular patches with the same ID are obtained and highlighted according to the ID value of the vertex of the triangular patch, so as to achieve the effect of selecting an object alone. The field that stores the ID value in the vector dataset is an associated field, and other fields can also be designated as associated fields.

Dynamic monomer

Different from the first two methods, dynamic segmentation does not need to preprocess the oblique photography model data. We load the matched two-dimensional vector plane and the oblique photography model into the same scene, paste the vector plane on the surface of the oblique model object when rendering the model data, and then set the color and transparency of the vector plane, so as to achieve the effect that the ground objects can be selected separately. If you want to make thematic maps, this method is quite convenient.