DSAA

The Distributed Spatial Analysis Architecture (DSAA) is a software solution that was conceived and designed by NFIS for analysing spatial and non-spatial distributed data (as represented in images). It was created in conjunction with NFIS software development team and external contractors. DSAA currently consists of eleven distinct service modules that can be used for performing analysis. The output from one service can be "chained" into the input of another service, allowing complex virtual services to be created. DSAA can acquire image data through a variety of means, including OGC-compliant WMS GetMap calls. Raw output from DSAA typically consists of images and/or XML documents, but this output can be styled into HTML and/or PDF reports.

DSAA consists of four major components:

1. The base component in DSAA is a set of service modules. Each module accepts image data and applies analysis or manipulation to that data, returning results as a new image and/or an XML report. They implement the functionality for a specific DSAA service. Modules are considered stand-alone as they can be used outside of the DSAA invocation framework.
2. The service handler component manages all input and output to/from all service modules. The handler is capable of styling service report XML (raw output) from individual service modules into HTML or PDF files. The service handler has been implemented so that:
   1. a variety of user interfaces (e.g. Web, GUI application, etc.) can invoke it,
   2. new service modules can be easily integrated, and
   3. remote Web services can be accessed.
3. A Web services interface has been implemented for selected services so that they can be invoked using HTTP/S by other software applications. Service requests made to this interface are forwarded to the service handler, returning and raw or styled output.
4. The Web-based user interface component is undergoing initial development and will allow a user to collect distributed data sets, invoke DSAA services, and store service results from within their chosen Web browser.

Service modules that are currently implemented can perform the following services:

1. Buffer - creates internal and/or external buffers around a specified colour in an image.
2. Colour Index - returns an XML report indicating the lookup table index for each colour in an image.
3. Colour Naming - analyzes an image and a set of uniquely named (x, y) coordinates returning a report that lists the supplied name and corresponding ARGB values for each (x, y) coordinate.
4. Colour Remapping - remaps pixel colours in an image.
5. Colour Renaming - analyzes image and dynamically generates an HTML form to allow user to specify unique names for ARGB colours; form is submitted to a servlet that then outputs report.
6. Image Overlay - overlays two images of the same dimension on top each another, producing a resulting image that has a new unique colour assigned for each occurrence of a colour pair in the overlaid image.
7. Mask - replaces specified color(s) in an image with another color.
8. Median Filter - filters an input image replacing each pixel colour with a colour determined by the particular filter being used.
9. Mode Filter - iterates through each pixel in an image, determining the mode (most popular colour) amongst neighbouring pixels, then writing that colour to an output image.
10. Neighbours - returns a report containing a count of the number of occurrences of unique colour value pairs that are either horizontal or vertical neighbours.
11. Pixel Area - given a bounding box, a CRS and an image, the service calculates the area covered for all or specified colours in the image.
12. Thumbnail - creates a scaled thumbnail from an image.

In addition, a prototype virtual service has been created - known as IOPA. This service transforms the output from the Image Overlay service into input to the Pixel Area service.

DSAA can be used by researchers, policy analysts, and members of the public for deriving "value-added" information from spatial and non-spatial data sets. It is hoped that NFIS and CFSNet partners will be able leverage their own analysis tools using the Web services interface to invoke DSAA services.