wiki:BluePrintGISFeatureLayers

Feature Layers

  • A 'Feature' is a Resource Record which has a Lat/Lon available.
    • If a Lat/Lon is not directly attached to a Location, then it can be displayed on the Map by using the lowest-level of coordinates that are available within the hierarchy
  • Features can be Points, Lines or Polygons
  • Features can be added to the Map
    • A Feature Layer is a collection of Features for displaying on the Map or for exporting as a feed
      • Resource
      • Filtered
        • Resource.Category (Report/Incident table, Missing Persons, L0->L3 in gis_location table)
      • Collection of Resources <- is this required?
        • feature_layer can have a query on new gis_landmark table which pulls in categories Port/Airport/Railway
  • Features can be removed from the map or moved on the map interactively.
    • To do this via a single set of Controls means having a single Vector Layer (or having to manually select the active layer!).
      • Build up this Vector Layer from multiple Feature Layers
      • In order to be able to dynamically enable/disable individual Feature Layers whilst viewing the map, we need to write a custom layer switcher which refreshes the whole Features Layer client-side upon changes.
  • Feature Layers can be filtered interactively without a server-side call to rebuild the map.
    • Need the original Feature_Layer to contain the attribute which we want to be able to filter on. Can then use our custom layer Switcher to apply the Filter.
    • Alternatively, (re)build the Feature Layers via AJAX calls when filters are changed.
  • Feature Layers can be refreshed to reflect new DB content without a server-side call to rebuild the map.
    • rebuild the Feature Layers via AJAX calls when refresh required (either button or timer for a big window)
  • User can define which layers should be selectable/enabled-by-default in the Situation Mapping layer switcher.
    • This list is personalisable.
      • move from layer definitions to gis_config
        • Have 1->M for Feature_Layers for available.
        • Attribute of visible stored in a separate multiple field.
          • Combine with special widget?
  • Features can be exported in KML/GeoRSS/GPX/etc
    • Need to update S3XRC for GPS symbol detection when FeatureClass allocation changes
    • Need to update gis.get_marker() when FeatureClass allocation changes
  • We want to be able to report on resources aggregated by admin area
    • These should display clickable Polygons
    • Clicking on the Polygon provides an aggregated overview of the resources
      • Need a Report to provide the contents for the popup
      • add an option to list individual members.
  • We want to be able to define Layer Groups which collect a number of different resources together, each filtered separately & with different markers into a single Feed (for display on our map & for export)

Markers

A Marker is an image used to represent a Feature on the map.

The Marker used will be:

  1. Cluster marker if multiple markers close together
    • styled by size & include the # inside (when >2)
    • prevents performance issues as well as making things clearer
  2. The Feature marker (if defined)
    • Q: Is this required?
      • Removing it will make for a more consistent User Interface as the symbology can be trusted
      • Removing it will speed things up the operation of gis.get_marker()
    • Q: If kept, should we provide an option to allow the FeatureClass icon to over-ride individual Feature Icons?
  3. Styling based on values of an attribute of the resource
    • Need to be able to store these definitions within the FeatureLayer so that they are available not just to specific modules but also to the main Situation Mapping
    • Want UI to be able to choose the attribute, the values & the markers
  4. The FeatureClass marker (if defined)
    • This should be selected accroding to the currently active Symbology
  5. The Default marker

A legend should be added to the Layer Switcher to show which layer relates to which icon.

Markers BluePrint

Popups

Clicking a Feature should bring up a Popup

  • This can be a URL to load (flexible, but slow)
    • define the URL in FeatureClass? FeatureGroup?
    • Future: allow inserting a per-feature popup_url into the query before passing into API, e.g.
      features_query = db(query).select()
      for feature in features_query:
         feature.popup_url = URL(c="vol", f="vol") + "%(location_id)s"
      
      • Support string substitution like %(location_id)s
        • the onFeatureSelect control is per-layer not per-feature & so feature-specific aspects need to be evaluated client-side in Javascript.
  • If not provided, the default is:
    • Loaded into the map during main load: no server-side calls
    • Header should be found from a set of common options (name/code)
      • How to do this with JOINed queries?
    • All the list_fields with their labels
    • A link to open the record in a new tab

Clicking a Cluster should bring up a Popup

  • a list of the features within the cluster
    • each list item is hyperlinked to bring up the Feature's Popup
  • Option to Zoom In

Q: Provide option to add Labels to Features?

Implementation

Option A (preferred)

Hardcode the link between FeatureClass & Resource (with optional category, e.g. for 'Report/Incident' table)

  • Add optional category_field/category_value columns to the feature_class table
  • If wanting feature-specific markers then add marker_id to resource tables (by bundling with location_id)
  • Replace feature_group table with feature_layer table
    • fields:
      • name
      • resource (used to populate the query field via an 'onvalidation')
      • filter_field (optional. used to populate the query field via an 'onvalidation')
      • filter_value (optional. used to populate the query field via an 'onvalidation')
      • query (hidden behind 'Advanced' button?)
      • marker_id (optional: over-ride all markers for this query)
      • comments

Option B

FeatureClass is an attribute of the link table

  • location_id extended to include feature_class_id (& marker_id) fields
  • => a Feature Group cannot be a collection of Feature Classes since we can't trawl through all resources to see if any of them have been tagged for this FC

Storage

BluePrintGISStorage

Docs

Examples

Limitations

Implementation Notes

The Draft features layer (draftLayer) is not in featureLayers (& hence not in allLayers)

  • This was done to stop the highlightControl being active (although that could have been done through an exception into tooltipSelect())
  • This potentially means we can have the separate selectControl()
  • What do we gain from being in allLayers?
    • shared Toggle for popups
    • What do we gain from being in featureLayers?
      • Potential shared clustering?

GIS BluePrints

Last modified 10 years ago Last modified on 01/06/12 23:44:00
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