Product Name:  Cached Map Services (BETA)

Description: VCGI has developed a suite of cached map services. The services consist of pre-generated map tiles at various scales. These services allows VGIS users to leverage the performance benefits of basemap and image caches to improve productivity. The services can be used within ArcGIS Desktop and/or to build web-based mapping applications (eg: map mashups).

Available Cache Services

  • VIL_CACHE_COLOR_SP: "Best available" color imagery in VT State Plane coordinate system (NAD83 - meters).
  • VIL_CACHE_COLOR_WM: "Best available" color imagery in Web Mercator coordinate system (Google/Bing projection).
  • VIL_CACHE_PAN_SP: "Best available" panchromatic (black & white) imagery in VT State Plane coordinate system (NAD83 - meters).

Software Requirements

Using Cache Services within ArcMap:

  • Use the following procedures to utilize the map cache services in ArcMap.
    • Startup ArcMap 9.3+
    • Click the "Add Data" button.
    • Browse to "GIS Servers" icon in your catalog, then double click "Add ArcGIS Server".
    • Select "Use GIS Services", then Next.
    • ServerURL = http://maps.vcgi.org/arcgis/services then click finish.
    • Browse to "ArcGIS on maps.vcgi.org". Browse to ./basemap_services folder.
    • Select one of the VIL_CACHE_* services

Mashup Samples
Here are a couple of samples that show how to incorporate the cached imagery services into a simple HTML/JavaScipt based website. To download the sample code just follow one of the links below, right-click on the page and select "View Page Source". Select "File -> Save As" to save file. Save as HTML.

Limitations

  • You must have a broadband connection to use these service.
  • The VT State Plane cache services cannot be combined with Google or Bing mashups since the later are in Web Mercator.
  • Cached tiles have been generated in JPEG format. This improves performance while reducing storeage requirements. However, it also means that the areas outside the state with no imagery will render white. This can be annoying in certain situations.
  • Image quality is limited by a number of factors including, 1) quality of original imagery, 2) JPEG quality parameters, 3) and reprojection of imagery during cache generation.
  • Users cannot turn on/off individual imagery datasets contained in the cache. What you see is what you get.

Known Issues & Bugs

  • The cached imagery services are initially very slow when you first load them into a ArcMap session. After that it should be reasonably fast depending on your broadband connection speed. ESRI Technical Support indicated that they weren't able to replicate the problem, however, VCGI and other testers have replicated the problem many times. We hope to resolve this problem in the future.

Disclaimer:

  • VCGI and the State of Vermont make no representation of any kind, including but not limited to the warranties of merchantability or fitness for a particular use, nor are any such warranties to be implied with respect to these services.


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