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What is more efficient for an IMS site: labels or annotation? And explain why.

October 05 2007 | 0 comments
Categories: ArcGIS Methods

Please tell me what is more efficient for an IMS site: labels or annotation? And explain why.

Mapping Center Answer:

It really depends on the nature and functionality of your site. If the map is intended to be zoom-able, then labels are often a better option; though your placement options, particularly some of those with Maplex (if you’re using ArcGIS server; like font reduction and “best” versus “fast” placement) present a trade-off in quality for speed. If you’re using the older IMS AXL files, then quality will be limited anyway and it’s a matter of performance for the labeling options you’ve selected.

Annotation is fine, if the map is not zoom-able or if you’ve got the time to produce annotation at several scales and set up scale ranges to display the annotation. Annotation draws faster and you can customize (via manual editing) placement of text in tight spots. However, annotation is not a good option if you’ve got dynamic data and need to show the current state of your data on your site.

There’s also a learning curve to setting up labeling rules and the more experience you have, the better and faster things can be done. The second best of all worlds is to have all your labeling rules saved in your AXL code (or a style if using ArcGIS server) so you can produce annotation each time your data is updated, and then republish the data behind your site periodically, perhaps weekly or monthly.

That said, my recommendation as being the best method, is that if you can get labeling to work well, i.e., you use ArcGIS server and have traversed the Maplex learning curve, use the ArcGIS server map cache functionality we released at 9.2. That allows you to use annotation or labels; or a mix* of the two. The main reason is that you are producing a multi-scale cache of your map ahead of time, so the clients are just downloading the images, no draw time on the server is involved. The Generate Map Server Cache tool allows you to create tiled images of your map at several scales, the best part is that you can use whatever you need to draw the features, even if it’s slow, as you produce the cache only once, and all the clients of your site are just downloading the pictures of your map, so draw time is optimized.

*There are certainly some potential complications with mixing anno and labels; based on the idea that the annotation may be occupying space on your map that might be better used for labeling more important features.

That said, I know you asked for recommendations for an IMS site, and the Map Server Cache is for ArcGIS server, so my earlier discussion was meant to answer your question as asked, but if I had my way, I would not use IMS (the drawing technology is a decade old and does not offer, in my opinion as a cartographer sufficient quality in many cases). But, that assumes many things about how much time and what software you have licenses for, etc.

Hopefully that will help you in the near term,

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