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In response to comments, I'll rephrase the question:

We're building a web based mapping and data querying system. The data are at several different scales, and should be queryable at these scales. The data itself should be searchable, based on key identifying features (names, etc.). The application is aimed mostly at a presentation level, so for serious analysis of the data search results should be available for download. If possible a interactive selection of features should be available for download also.

For preference we'd like to develop the app using an open source web mapping app, such as open layers, or mapfish.

Our key features beyond the basic pan/zoom are searching the data based on attributes, and downloading the data. Given that several frameworks implement search, can anyone suggest a web mapping framework where data download has been implemented, or an example of an online web map with this feature?

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For me, there's a fairly large gap between 'a web map' and a 'web-based GIS': a simple map with layer control and panning is great for many applications, but doing analysis through the web is a different scope which many web maps don't attempt to solve. Are you interested in doing analysis or primarily display? –  scw Aug 9 '10 at 23:18
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Your description is analogous to someone attempting to build a vehicle. "It should start with wheels, have some lights, and some safety features. What else is necessary?" I don't know, will you be transporting things or people? Is it just point A to B or does it need to travel in style? Similarly, a "key feature list" for a GIS app is going to depend on what exactly the app is going to be used for. –  Michael Todd Aug 9 '10 at 23:23
    
See also gis.stackexchange.com/questions/8032/… –  Bryce Jan 30 '12 at 17:00
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2 Answers 2

up vote 13 down vote accepted

As suggested by the comments, you've got a lot of options in selecting the components that make up your web mapping application. OpenLayers is a good choice for a client-side mapping library. OpenLayers is not going to provide you with a rich set of widgets for your GUI.

Depending on whether this application is going to be integrated into an existing site, whether you want it to look like a more traditional desktop application, and where your front-end development skills lie, you can choose from widget libraries like jQuery UI, Dojo, and Ext JS. If you choose Ext JS, the GeoExt project provides a library that brings mapping functionality from OpenLayers to Ext JS applications.

And all that is just a limited set of your choices for the front end. On the back end, you want to set up services that are configured to work with your data and communicate via standard web mapping protocols with the client side. GeoServer and MapServer are two common open source mapping servers. You can read about the various features of each elsewhere, but both bring OGC Web Map Service (WMS) and Web Feature Service (WFS) implementations to your application. One benefit of using open standards is that you can swap out components of your application (in this case, the mapping service component) and the rest of your application can work without modification (in this case the client and database).

The query and feature interaction you mention above can be addressed by WFS functionality. WMS allows for rendering of your data on the server (to be displayed as map tiles on the client). And, regarding download, GeoServer allows clients to request data (for download) formatted as shapefile, KML, and more.

Below the mapping services, you'll need a place to store your data. You can store data on the filesystem with shapefiles, or you can use a spatially enabled database. PostGIS brings spatial functionality to the PostgreSQL database and is a popular open source option.

In most cases, even if someone sends you a link to an application that does bits of what you want, there will be "some assembly required" for you to put together the parts in a way that meets your needs.

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Thanks for that Tim. We've got the backend sorted - using MapServer to serve WMS and WFS. At this point we're really looking at how to implement the front end. –  om_henners Aug 10 '10 at 22:53
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Just read your comment above, so this is a little late now.

But this is somthing we have been looking at as well, we are developing a solution using MapGuide http://mapguide.osgeo.org/. It makes use of Feature Data Objects and have used that to convert and download sections of data. FDO allows access of data from a nmuber of spatial databases, Oracle, MS SQL, SQLite and PostGIS as well as file format SHP, SDF etc. It also makes use of openlayer.

It has exstensive API which can be developed in Java, .net and php.

May be worth keeping it in mind for future

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