Nowadays, the acquisition of images has become more and more convenient and efficient, and the demand for the management and service release of massive images has become more and more common. In order to complete this work more conveniently and efficiently, provided.
Mosaic Dataset is managed by metadata + original Image Files. When adding Image Data to Mosaic Dataset, only the path, contour, resolution and other meta-information of Image Files will be recorded in Mosaic Dataset, and the required Image Files will be loaded according to the meta-information when using. Compared with the traditional warehousing management mode, this mode greatly improves the speed of warehousing and reduces the occupation of disks.
Mosaic Dataset features
- Data in different raster formats can be managed: Mosaic Dataset is used to manage data in raster format. Images in different formats (*.tif, *.tiff, *.img, *.ecw, *.pix, *.sid) can be added to the same Mosaic Dataset. And a large numb of images can be adde at a time.
- Sub-Dataset coordinate system shall be consistent: The images added to Mosaic Dataset may have different coordinate systems. For example, in the global image Mosaic Dataset shown in the following figure, the coordinate system of the original image file is UTM zonal projection based on WGS1984. In order to display the images dynamically, Here, you need to set the Projection Settings as their unified GCSWGS1984. Therefore, you need to specify its coordinate system as WGS1984Geographic Coordinate System during Build Mosaic Dataset.
Figure: Using Manage Mosaic Dataset Global Image Data - High storage efficiency and small disk occupation: Manage Mosaic Dataset mass images are used, which not only has high image storage efficiency, but also occupies small disk space. Test Show Results: Global DEM Data with a resolution of 30 meters, with a 22667 of 0.98 TB. Importing all at once to UDBDatasource took 14 minutes; after importing, the UDB file was 16 MB and the udd file was 22 MB
Figure: Using Manage Mosaic Dataset Global DGM Data
Preparation for use
Before adding images to Mosaic Dataset, you need to know the basic information of the images to be stored, including the size of Image Files, the number of files, and whether a pyramid has been established, so as to make adequate preparations for image storage.
- Image Files size and number of files can be used to estimate the time and disk space required for image storage operations.
- Whether the pyramid is created for the image and whether the image is stored in blocks can significantly improve the display efficiency of the image. The construction of Image Pyramid and the conversion of the image into block storage can be completed before or after the storage.
- Image pyramid construction and block storage conversion, as well as post-image Map Cache generation, all support multiple processes. Therefore, in order to achieve higher execution efficiency, a machine with higher configuration can be prepared to perform these operations.
- The above mainly considers the various resources required for image storage. You also need to know the image itself. Whether the content recorded by the image is the pop reflection of the ground object or the elevation, which involves which display method is used for the image Map in the later stage. For example, for DEM Data, the elevation classification can be displayed through the color table and the three-dimensional shading effect.
- View Image Projection : During Build Mosaic Dataset, in order to enable the image to be spliced and displayed efficiently and correctly in the Target Coordinate System, First, You need to know the coordinate information of Image Files (directly open Image Files in the Open File Datasource mode, and you can query the coordinate system information in the Dataset Properties information). And determine the coordinate system required for Mosaic DatasetShow in Map, for example, Image Files itself is China2000 zonal projection, the coordinate system for map display needs to be China2000, and the coordinate system for actual map display may be inconsistent with the Image Files coordinate system. The following describes how to set the appropriate coordinate system for Mosaic Dataset from the original Image Files with and without coordinate system:
- When the original Image Files has a coordinate system and is inconsistent with the coordinate system required for map display, it is recommended to set the Coordinate System Settings of Mosaic Dataset as the coordinate system required for map display.
For example, the image Original Coordinate System is China2000 zonal projection, the coordinate system required for map display is China2000, and the coordinate system for Build Mosaic Dataset is set to China2000. Because the map will automatically convert the image from China2000 Projected Coordinate System to China2000 coordinate system when it is displayed, users do not need to do additional coordinate system processing. Compared with setting the Mosaic Dataset as the China2000 zoning Projected Coordinate System with the same coordinates as the Original Image, and then setting the map Dynamic Projection as China2000 during display, The former way shows higher efficiency. Therefore, it is not recommended to use Dynamic Projection for maps when using Mosaic Dataset.
- When the original Image Files has a coordinate system and is consistent with the coordinate system required for map display, it is recommended to set the Coordinate System Settings of Mosaic Dataset as the coordinate system required for map display.
- When the original Image Files has no coordinate system (Planar Coordinate System) but the coordinate system of the data is known to the user, there are the following handling methods:
(1) Do not process the original Image Files, and set the Coordinate System Settings of Mosaic Dataset as the coordinate system of the data. In this case, the map Display Coordinates must be consistent with the data coordinate system. For example, Original Image has no coordinate system (Planar Coordinate System), but the user knows that the data is China2000 zonal projection. Then the Coordinate System Settings of Mosaic Dataset is projected as China2000. In subsequent use, the coordinate system displayed on the map must also be China2000 zonal projection, and the map cannot use the Dynamic Projection function. Because the original Image Files lacks a coordinate system, the automatic Projection Transformation cannot be performed inside the program, and the image cannot be displayed normally.
(2) Give the data Coordinate System Settings known by the user to the original Image Files, that is, process the original Image Files into the case with a coordinate system. Refer to 1 and 2 for Coordinate System Settings for subsequent Mosaic Dataset.
- When the original Image Files has a coordinate system and is inconsistent with the coordinate system required for map display, it is recommended to set the Coordinate System Settings of Mosaic Dataset as the coordinate system required for map display.
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