What Problem Does This Solve?
Extract geographic data for a specific region.
When to Use This Pattern
User needs to acquire data for offline use or further manipulation and therefore requires the ability to extract a region of the results into a downloadable bundle. Depending on the nature of the data and the provider capabilities a user should be able to refine the output format settings and delivery methods.
What’s the Solution?
A typical extract process follows this process (not all steps need to be included at all times):
- Select area of interest (form input, polygon, freehand, select boundary)
- Select layers to extract data from
- Specify output parameters (coordinate system, output format)
- Specify download format / delivery method
- Compare / Preview
- Extract data
- Present confirmation (download link / email notification)
Locating the area of interest can be done through a locator while the actual selection of the area to download could be the current extent by default, followed by selecting by a standard geography (block group, parcel, city boundary) or by using a selection tool (typically rectangular selection).
Why Use This Pattern?
A common service for a spatial portal is to deliver data to a user. Data may be vector features (points, lines, polygons) or raster imagery. Data can be raw or processed and depending on the selected region encompass any combination of above, i.e. multiple layers.
A multitude of options need to be considered to provide not only an experience that fits the target audience but also the service provider. Following is a list of parameters that will affect how the data extract is implemented and presented:
- Discovery methods available? Is a locator available? Can common places (bookmarks, maybe of already processed locations) be shown?
- Metadata about selected area: What data is available at which precision?
- Selection methods available: How will clipping occur and how can the user specify the clip area?
- Clear selection: How will the user specify that the task is completed or abandoned?
- Output format: Which formats exist? Projection?
- Output options: Mosaic? Precision? Year of data?
- Data Extraction: On the fly? Already prepared for common areas?
- Target space: Is enough mailbox space available if sent through mail?
- Bundle space: How long will the data be available for download? Is enough server space allocated?
- Delivery options: Download/Email/…
- Other considerations: Data bandwidth restrictions? Paid service? Authentication required? If extent too big (state-wide), call us…
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References and further reading