GIS to get information for specific bb box/zoom level

Please feel free to correct any miss used words in this post, as I'm not familiar in such areas, I use words to the best of my knowledge but they're probably wrong.

So here's what I want to do:

Child abducting and trafficking is a quite serious problem back in China, a friend of mine was talking to me this afternoon, the idea of a separate app on iOS and Android to do this task, users can take pictures, upload along with their GPS location 开发者_开发问答to a db, and the app can also display information that's in the db, as annotations on a map.

And my question is:

In the app when user submit a new post, which includes photos, GPS location, any notes, to a database.

Then we user switch to map view, we'll have to get information for the current zoom level/bb box, so

how should I store those information in the db, in what format?

and

are there any open source tools that can parse the information for given bb box/zoom level and return a xml file so that I can take and use it to display the information?

-- I found GeoServer, are there better ones for my use? I really only need it to generate xml files based on bb box/zoom level.

I would imagine that host the tool (is it called geocoder?) on Google App Engine/Amazon Ec2 is the most ideal, don't know much for db, probably Amazon Simple DB?

Thanks!

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There are a number of Open Source tools that could help - you could look at GeoDjango, for example, which can use the PostGIS geo database - but honestly, for this application, you don't need anything geo-specific:

• You will be receiving GPS coordinates in latitude/longitude, so presumably you'll have a table in your database with two columns, latitude and longitude.

• To do a bounding box lookup, all you need is the minimum/maximum for both longitude and latitude (which any web-based map will be able to give you). Once you have that, almost any SQL database will support a query like this:

  SELECT * FROM records 
      WHERE latitude >= $min_lat 
          AND latitude <= $max_lat
          AND longitude >=  $min_lon
          AND longitude <= $max_lon;
  

  This gives you a list of records that falls within your bounding box.

• Now you can use whatever middleware you like - a CMS system like Django or Drupal, a custom PHP script, etc - to turn the resultset into XML or JSON format.

Geographic databases do a lot of things relational databases don't do easily, like find points within a radius or points within a set of polygons. But you don't need that for your application - any system with basic database-querying functions should give you what you need.