ArcGIS Cache Technology (zz)

Abstract:Map cache is an effective way to quickly access the map service. Currently, popular online maps such as Google Maps and mapbar provide efficient MAP access speeds by caching maps. ArcGIS cache technology provides basic technical guarantee for enterprises and public GIS applications.

Map cache is an effective way to quickly access the map service. Currently, popular online maps such as Google Maps and mapbar provide efficient MAP access speeds by caching maps. ArcGIS cache technology provides basic technical guarantee for enterprises and public GIS applications. Let's take a look at ArcGIS cache:

1. ArcGIS cache service

ArcGIS
Server cache services are available in 2D and 3D formats, providing services for 2D and 3D maps respectively. Based on application requirements, it can also be divided into integrated cache (1), multi-layer cache, and on-demand cache. Integration
Cache generates slices by groups of all layers. Multi-layer caching creates a slicing block for each layer. The client can control layer display, tagging, and element selection. On-demand cache does not generate slices beforehand,
Creating slices Based on the client's first access request can save space and cache creation time.

// This is the original directory description. Added by zhangjun at 2011-1-6

 

Figure 1: ArcGIS cache scale and integrated cache structure

The ArcGIS Server Cache consists of directories and configuration files and is named according to certain rules, such as LXX, rxx, and cxx. ArcGIS support and ArcGIS
Online, Google Map, virtual
Therefore, the cache can be created based on the Gmaps or vw scale rules to implement map integration applications.

Ii. ArcGIS cache Tool

ArcGIS provides a complete cache management tool. You can create, delete, and update caches in arccatalog. You can also use toolbox tools to manage the cache, as shown in figure 2.

Figure 2: ArcGIS cache Tool

ArcGIS supports creating cache within the full graph range, or creating a cache map within a certain MAP range. In section 9.3, ArcGIS provides more methods to create or update local map caches based on a certain element range, for example, within a certain province.

ArcGIS can manually enter the scale of the cache to be created, or directly enter the level of the cache to be created, for example, level 10, and the scale is automatically allocated. ArcGIS can save the created cache level as a configuration file for direct calling or sharing next time.
For maps that reach the national level to a certain county or township level, it is necessary to create multiple caches of different scales and levels at a large time cost. ArcGIS can create different scales on multiple machines and copy the generated cached map to the same structure directory, saving time and cost. This is also applicable to map updates and keeps the map updated quickly.

 

Iii. Key Concepts of ArcGIS Cache

(1) tiling Schema

The slice structure includes the scale level, slice scale, and cache slice origin. You can select several methods for the slice structure:

Load from online map services, such as ArcGIS online, Google Maps, or Microsoft Virtual Earth
Load from existing map service
Load the tiling schema file
Create your own tiling Schema

(2) Scale

When creating a slice structure, you can customize the scale or make ArcGIS
The server recommends some scales based on the power of 2. For example, if the current scale is, 000,000, and three scale levels are defined, the system automatically recommends the following three scales:
Ruler: 1: 128,000,000; 1: 64,000,000;, 000,000.

(3) tiling schema Origin

The origin of the slice structure is the upper left corner of the slice structure grid. In most cases, maintain the origin point selected by the system. If the map document does not define a coordinate reference, the system selects twice the maximum range of the map as the map origin.

Figure 3: Slice Structure Origin

(4) block width and height

The default width and height are 512 pixels. You can select its multiples, such as 256 or 128. ArcGIS
Online is 512x512 by default, virtual
Earth uses 256x256. The minimum size of a Windows disk is 4 K, that is, the size of the same image. 256 requires 16 K space, and 512 requires only 4 K space. Therefore, we recommend that you use
512x512.

Figure 4: block height and width

(5) Anti-sawtooth

Anti-sawtooth is an image processing technique that uses foreground pixels close to the edge of the background to make the eyes look smoother. ArcGIS
The server cache does not use real anti-aliasing, but does similar work to make the labels, unfilled lines, and polygon elements look smoother. If you are doing vector layer and image superposition, be careful to use
This tool. The background color of the Data box depends on the color of the anti-sawtooth element. By default, the color of the background box is RGB.
253,253,253 (almost white), which causes the anti-sawtooth elements to become white intentionally, especially when a dark raster layer is placed, such as a normal image. The most effective way is
Change the background color to a dark color.

Figure 5: Anti-sawtooth

(6) DPI

DPI indicates Dots Per
Inch indicates the resolution of the cache block generated by the server. DPI depends on the user's screen resolution (such as 1024x768) and physical size (such as, 19 "inch ). DPI difference on the client machine
Don't be too large, because large screens (low DPI) and high-resolution screens and graphics cards (the corresponding DPI can be increased through settings ). If the client needs to print maps frequently, including your cache layers, you will
It is helpful to increase DPI, but note that this will also increase the cache file size.

When DPI is selected, the default value is 96, which is usually enough unless you work on the network and your client machine has different DPI.

Iv. Use Cache

(1) Web ADF
 

Figure 6: Access to the cache using the ADF

6. You can use the ADF to determine whether a cached map exists and access the cached map locally or on the Internet.

(2) ArcGIS Application

The ArcMAP, arcreader, arcglobe, ArcGIS Explorer, and ArcGIS mobile applications can all access the ArcGIS cache map service.

(3) Open API

You can access the cache map service of ArcGIS through open-source APIs, such as flex, openlayer, and rest APIs.

 

V. Summary

ArcGIS cache technology is combined with GIS comprehensive technology to provide powerful technical support for enterprise applications. The following points are summarized:

(1) The cache service type meets the multi-faceted application requirements. ArcGIS provides two-dimensional and three-dimensional caching technology, and supports integrated caching, multi-layer caching, and on-demand caching based on application requirements to meet actual needs.

(2) rich cache management tools. With the ArcGIS function, you can create a cache based on the full graph, region, and element range or the specified or recommended scale. You can also use the geoprocessing function to customize the cache plan.

(3) ArcGIS can implement cache and non-Cache map superposition, or cache as needed.

(4) ArcGIS cache supports the combination of Google Maps and Virtual Earth and is available for other open-source applications.