Our previous post on using custom basemaps generated some additional questions which we’ll cover this week. One reader asked if it was possible to use a shapefile as the source of your custom basemap. The answer is: not directly, but you can apply a little trick and accomplish this by using transparency in your existing basemap. Note that Explorer Online currently does not allow you to adjust basemap transparency, so we’ll author the map using the ArcGIS.com map viewer. The map we author there with basemap transparency can be used in Explorer Online, and other applications.
First, zip the shapefile you want to use and add it to your map. Using the ArcGIS.com map viewer click Add, then Add Layer from File.
Once you’ve added the shapefile, symbolize it as desired. In the example below we’ve used a shapefile with climate data for Yellowstone National Park.
While we can’t remove the basemap, we can set the transparency of the basemap to %100, in effect isolating our shapefile as the basemap.
Here’s our map (with invisible basemap) in one of the application templates:
Note that this is more of a trick than a supported feature. When importing shapefiles to your web map you are limited to 1,000 features, and your performance mileage will vary depending on the browser you use (Chrome and Firefox work best). The best way to use shapefiles of any size as basemaps (or pretty much anything else for that matter) is to publish them as services. Right now that means using ArcGIS Server, but very soon you’ll be able to publish services using an ArcGIS Online subscription account (this is currently in beta).
However, for small numbers of features this can be an effective way to use a shapefile as a basemap, especially when using the web map in custom applications.
