Summary of map layer loading 2021.4.15
Commonly used map development platforms
1、ArcGIS
Mapping software is inseparable from ArcGIS. In the process of using ArcMap, it is good for vector data (.shp and .layer) or raster data (.tif). If there is a spatial reference (geographical coordinate system or projected coordinate system), during the process of adding a new layer, you will see that the newly added layer is on the top layer in the TOC (Table of Content) window on the left, and in the figure The order in the layer is 1, and it will flash once during the loading process, which further explains that the loading and storage of map layers is like a stack, and the layer added first will be placed at the bottom of the layer, and then the new Added layers are always on top of the stack.
2、ENVI
I have learned the professional software ENVI for remote sensing image processing. In ENVI, multiple layers can be loaded and data of multiple bands can be displayed, but the newly added layer will always be placed on the top layer, that is to say, its layer The number is 1, and the earliest loaded one will be placed at the bottom of the layer, and the corresponding layer number will be later, and it will flash at the moment of loading. In fact, all these layers will have temporary variables to save during operation. Processing speed and performance are related to the computer's CPU and memory size.
3、OSGEarth
During the OSGEarth development process, no matter whether it is to add layers through the API method Map to addImageLayer, or to read all layers through the .earth file (xml format), and then in the map interface of the platform, if the developer wants to add dynamically Layers can only re-initialize the map, create a new myMapNode, and then add multiple layers to reload the map through myMapNode->getMap()->addImageLayer("myclassfication.tif", myclass), and the results are relatively Effective, able to control the hiding and display of layers. Therefore, it is not difficult to understand that it is really wise for OSGEarth to load layers through .earth files. OSGGroup can add multiple Node objects. There are various Nodes in OSG, among which MapNode is a kind of Node, which is responsible for managing all the elevation layers ElevationLayer, image layer ImageLayer, slice layer TileLayer, etc. in the corresponding Map, so To realize the dynamic loading of the Tif image layer is actually a process of reinitializing the MapNode object. Moreover, OSGGroup in OSG is a tree management structure, which contains multiple nodes of various types, and each Node node manages the corresponding layer object.
