When we started building Fulcrum, offline capability was one of the core features we built into the software. We’ve put a lot of work into making the mobile app work completely offline, including offline basemaps, a feature I’d like to discuss in this post. Creating offline basemaps is a complex subject and worthy of several blog posts on it’s own, but I wanted to talk about MOBAC — a tool that allows you to create Fulcrum-compatible MBTiles basemaps from some common online sources like MapQuest Open, [OpenStreetMap],(http://www.openstreetmap.org/) and CloudMade.
Mobile Atlas Creator (MOBAC) is a general purpose tool to create offline maps in various file formats compatible with mobile applications. One of the formats it supports is MBTiles, the format that Fulcrum uses for offline basemaps. Using MOBAC, you can select a bounding area of an online tile source and create an offline-ready basemap that you can upload to your Fulcrum account. This is great if all you want is “cut out” of an existing online tile source.
First, you need to make sure your computer has Java installed. If you don’t have a Java runtime installed, you can download and install Java from Java.com. Then, you can download MOBAC from the web and extract it somewhere on your local computer. Because MOBAC is a Java application, it doesn’t need to “install” like a conventional app. You simply extract the zip file somewhere on your computer and you can run the ‘Mobile Atlas Creator.exe’ file if you’re on Windows, or double click Mobile_Atlas_Creator.jar if you’re on a Mac.
When you first open the application, you will be prompted to create a new atlas project. Start by entering a name and picking MBTiles as the format.
Once you get into the application, you will see the map in the main pane where you can navigate around and select your bounding area. Note: since clicking and dragging is used to select a bounding area, you have to hold down CTRL key and drag to pan the map.
Once you have an area selected, you can give it a “Layer Name” and click the “Add selection” button to add that area to your map. When you’re ready to start creating the offline map, click the “Create atlas” button.
The download process can take a while, depending on the size of the area and the number of zoom levels selected. In general, each successive zoom level is about 4 times the number of tiles than the previous zoom level. So zoom 17 takes approximately 4 times longer to download than zoom level 16 for the same bounding area. You can play around with the settings to get the best balance of zoom levels and area for your map. I would recommend not selecting an area larger than a city if you want a map with street level detail.
To get your map working in Fulcrum, all you need to do is upload it to your web account. From the web, login to your Fulcrum account and click on Offline Maps from the menu in the top right to start uploading your map. Once you’ve uploaded it to your account, you can sync your account from the iPhone or iPad app and you will see your new map available for download.
MOBAC is great if you want an offline basemap with standard map features. For more advanced offline maps, including custom data and styles, the next step is to checkout TileMill — A complete map design studio for Mac, Windows, and Linux. It allows for complete customization of the entire map using your own data with advanced zoom-dependent styles. It can export an MBTiles file that will work as a reference basemap in Fulcrum for data collection.