Ved den nys overståede ESRI bruger konference var jeg til en session (http://gisdk.blogspot.com/2008/08/esri-uc-day-2-framework-for.html) hvor der blev snakket meget om de dele som et kort er opbygget af: grundkort og operationelle kortlag. Grundkortene er dem man med fordel kan cache på forhånd, men det er også de kort man bør designe med stor forsigtighed. Hvad er synligt hvornår og hvorfor osv. Nedenfor er beskrevet en hel strategi hvorledes dette gribes.
At the ESRI User Conference I attended a sesssion (http://gisdk.blogspot.com/2008/08/esri-uc-day-2-framework-for.html) in part about base maps and operational layers. The base maps can and should be cached but the base map design should be carefully thought through. When should layers be visible and why. Below is described a design strategy on how to create good base maps.
Web maps often contain a base map, which provides a geographic frame of reference, and operational (or thematic) layers, which show a focused item of interest on top of the base map. A familiar example might be an online mapping service that provides real time traffic information on top of a city street map. The street map is the base map. It doesn’t change much and can be used for many purposes. The traffic information is the operational layer because it frequently changes and has a specific purpose and audience. This article describes different patterns for building Web applications that overlay base map and operational layers.
Base maps and operational layers often require separate strategies for effective maintenance and display in Web maps. When creating a Web map, it’s a good practice to separate the base map from the operational layers. Base maps generally require little maintenance and should almost always be cached, whereas operational layers may require creative strategies to present the most current data in a high-performance way.
Separating your base map and operational layers requires that you create at least two map documents (.mxd’s), which you subsequently publish as two distinct map services. Each becomes a map service layer in the overall Web map. A map service layer originates from a map document that may itself contain many layers.
This may seem strange to you if you’re new to Web mapping; perhaps your company has one map document with dozens of layers that they’ve used for years. For performance and flexibility reasons, it may be time to break up that monolithic map document. When you create multiple map documents, each containing a logical group of layers such as base map features, cadastral features, and so on, you can publish them as separate services and target your display strategies for each.
Read more: http://blogs.esri.com/Dev/blogs/arcgisserver/archive/2008/08/05/Design-patterns-for-Web-maps.aspx