Discussion on ArcGIS Server cache, supertile and bundle

1 ArcGIS Server cache Principle

The map Slicing Technology of ArcGIS Server includes two modes: exploded and Compact. The loose caching technology is saved as a sliced file, each slice corresponds to an image in the corresponding cache path. In the latter form, the map slice is packaged into a file by bundle. Because the disk storage occupies less space, it is easy to copy, the advantage of low network traffic when calling slice has become the preferred method for the current map service cache. This article will explore the scope of the cut chart.

First, you need to understand the arcgisserver's Cropping Mechanism. At a specific scale, the server will generate a large range of supertile, Which is 2048*2048 in the anti-aliasing state, and vice versa, it will be 4096*4096, then, slice in this range. For example, if the slice size is set to 256*256 pixels, the slice will be cut into 8*8 slices after a supertile is determined, the generated slice file exists in a bundle file in compact mode. A bundle can save 128*128 slice files. Both supertile and bundle are calculated from the slice origin.

In other words, at the same scale, a bundle can save 8x8 anti-sawtooth supertile, and each supertile can be cut into 8x8 slices; the next bundle with non-anti-aliasing stores 16*16 supertiles, each of which contains 16*16 slices.

2 supertile and bundle

To facilitate understanding of the concepts of supertile and bundle, the following experiment is conducted. A nationwide administrative area chart is used as an example.

1) First, generate a map slicing solution and use the generate map server cache tiling scheme tool to create

Several important parameters are set here, including the project document to be sliced, the output XML format slicing scheme, the designed scale level, and DPI parameters (96 by default) and slice size (256*256 ).

After the creation, you can open the created XML document to view detailed slice information, including space reference, start point, and scale classification information.

Currently, the map server cache tiling scheme to polygons tool provided by ArcGIS is used to create all supertile corresponding to the cut graph mode.

The supertile generated at all scales is as follows:

In its attribute table, you can see the scale, slice level, row and column numbers, and area of the slice.

Next, we need to export the supertile at a scale of 200 W, 100 W, 50 W, 25 W, and 10 W, and add a label and color field to identify the supertile.

The field calculator is used to assign values to color and label. The label value must display the row and column numbers of the slice. Color is used to mark the color of a specific slice. By default, 0 is assigned, unique value assignment for special identifiers.

Now we mark the supertile mesh layer to mark the slice in the third column of the first row. The effect is as follows:

In the same way, 100, 50, and 25 W are grid marked. The effect of the four labels is as follows:

What we are looking for now is the relationship between supertile and bundle. We can view the supertile corresponding to 100 W, 50 W, 25 W, and 10 W in 1 column and 3 slices under W downlink.

The next supertile with a scale of W contains two supertile with a scale of W,

The next slice of W contains 2x2 supertile of 50 W, and the next supertile of 50 W contains 2x2 supertile of 25 W.

We will review that under non-anti-sawtooth conditions, a supertile is 16*16 tile, the next supertile is 8*8 tile, and a bundle is 128*128 slices.

Combined with the above example, A supertile with a scale of contains (2*2) * (2*2) * (2*2) * (16*16) in non-anti-sawtooth mode) 128x128 tile.

Similarly, the next supertile at a scale of contains (2*2) * (2*2) * (2*2) * (2*2) * (8*8) A 10 W tile, that is, 128*128 slices.

Conclusion,

In non-anti-sawtooth mode, a supertile of the N-level scale is 128x128 N + 3-level tile;

In anti-aliasing mode, A supertile of the N-level scale is 128x128 Tile of the n + 4-level scale;

Non-anti-sawtooth slice is used. To generate a bundle mesh of 15 levels, you only need to use the map server cache tiling scheme to polygons tool to generate a supertile mesh of 12th levels.

Anti-sawtooth slice is used. To generate a bundle mesh of 15 levels, you only need to use the map server cache tiling scheme to polygons tool to generate a supertile mesh of 11th levels. 3. Create cache based on elements

After the experiment just concluded, it provides reasonable guidance for creating a cache based on elements. Generally, a small scale is directly switched to a full graph, and a small scale is switched based on a certain element range (in this case, the cropped graph uses the envelope rectangle range of the element ), in a large scale, it is split by elements that contain the grid.

At the same time, it is necessary to clarify the concept of the server cut graph implementation mechanism. When a cut graph is specified within the element range, all the feature values in the element class are processed in order, all service instances will collectively process a feature range and cut out all the caches that require a scale level within the range. Starting from 10.0, supertile is no longer used as the Worker Unit of the Service instance cut chart, but bundle is used as the processing unit, that is, an instance is responsible for the cut chart of a bundle range, that is, in order to make full use of the service instance resources, it is recommended that a feature range contain N bundle ranges. N is slightly larger than the number of service instances. The map server cache provided by ArcGIS Server
Tiling scheme topolygons solves the problem of element grid generation.

After the map service is published, you can use mangemap server cache tiles to manually manage the slice. You can specify the range of the cut chart at a specific scale. You can choose to slice by element or the envelope rectangle of the element.

1. cache by grid elements

Cut chart range:

2. cache by element envelope rectangle

Cut chart range: