Downloading Layers for Offline Use on the Mobile App

Please note: using the mobile app without a data connection requires a subscription to CalTopo or SARTopo. Basic subscriptions allow for downloading topographic base layers and pro subscriptions allow for downloading topographic and aerial imagery base layers. More information on the features and pricing of individual accounts can be found here. If you are looking for instructions on how to download base layers for offline use on the desktop app, those can be found here.

If you are looking for instructions on how to delete downloaded base layers, you can skip ahead to Deleting Downloaded Base Layers

Why Do I Need to Download Base Layers?

The purpose of this article is to walk you through the process of downloading base layers for use offline (which means no cell service or WiFi) on the mobile app. The reason you need to download base layers is because what we call a "map" in CalTopo is actually just saved map objects at specific coordinates. You need to view those map objects on top of base layers (such as MapBuilder Topo or Forest Service layers). When you have a data connection, you can access those base layers in the layers menu. However, when you don't have a data connection, you need to download base layer(s) for the area where the map is in order to view and navigate around that particular map.

So let's get started downloading base layers! The process is the same on iOS and Android although some of the icons may differ. Screenshots are shown for iOS mainly; screenshots for Android are included where icons may differ.

Step 1 Choose Where You Want To Download Base Layers

If you have a specific map that you want view offline, the first step is to open the map and center it in the map viewer. Make sure the entire map is in the map viewer. For example, let's say that I created a map for a multi-day backpacking trip through the Vogelsang Loop in Tuolumne Meadows. I would choose a zoom level that would allow me to see the entire map, as well as any other area I might be passing through, as shown below.

If you would rather just download base layers for a general area (i.e. the Wind River Range in Wyoming) rather than a specific map, you can can also navigate to that area as well.

Step 2 View Base Layer Coverage for an Area

Navigate to the Download Layers screen. Go to the 3 bar menu in the upper left hand corner, and choose Download Layers.

This will open the Download Layers screen. The 15x15 minute grid laid over the map shows individual quadrants. You can zoom in or out as well as move around the map as you normally would on your mobile device. The purple dotted rectangle shows the area you were just viewing in the map viewer.

The Show Coverage For drop down menu allows you to view the offline availability for different base layers. Some layers have limited geographic availability; for example the Forest Service layers are only available for US Forest Service and immediately adjacent terrain, and some aerial imagery layers do not have nationwide availability.

If layers are unavailable for a particular quadrant, it will be shaded red. This reflects only the availability of the layer selected in the Show Coverage For drop down menu. For example, the quadrants shown in red below do not have coverage for the Forest Service 2013 layer.

Any quadrants that you have previously downloaded base layers for will appear blue for standard resolution and purple for high resolution for the base layer currently selected in the Show Coverage For drop down menu.

Step 3 Select Quadrants to Download

Once you have an idea what layers are available for the area you want to download, the next step is to select the quadrants you want to download.

To select quadrants that you want to download layers for, simply click on the quadrant. Quadrants you have selected will be outlined in yellow as shown below.

If you select a quadrant that you don't want, simply click it again to deselect it.

Make sure to select all the quadrants needed to cover the purple dotted rectangle if you are trying to get complete coverage for what you were just viewing in the map viewer (either a map or particular area).

Step 4 Select Base Layers to Download

Now that you have selected the quadrants you want to download, the next step is to select the layers you want to download for those quadrants. Click the download icon in the upper righthand corner.

iOS Download Icon Android Download Icon

With the default settings if you are not connected to WiFi, a popup will open as shown below and ask if you want to download on cellular. Selecting yes will change you system settings for all downloads going forward and can incur carrier costs for downloading data. CalTopo is not responsible for any data costs incurred by users while downloading data.

The download screen will open and this is where base layers can be chosen for download for the quadrants you selected. You can select one or multiple base layers to download for the selected quadrants. It will be noted in red font if a layer does not cover the entire area selected for download. Select the base layer(s) desired. For this example, let's select MapBuilder Topo and NAIP 2012 Imagery.

Once a layer is selected, a drop down resolution menu will appear next to the layer as shown above. Available resolutions may vary layer to layer and based upon your subscription level. Download size is displayed at the bottom of the screen along with available device space and a visual representation of storage capacity. Be aware that downloading high resolutions of large areas will result in very large downloads.

Step 5 Download Your Base Layers

When you are happy with the layers and resolutions that you have selected, select Download at the button of the screen. The Download Layers screen will open again and the map tiles for the selected areas will download. The quadrants will turn blue for standard resolution and purple for high resolution once the download is complete.

You can return to the Download Layers screen at any time to check which layers you have downloaded in particular areas.

To return to the map viewer, press Map in the upper left hand corner of the screen. You can now view synced maps without a data connection in areas where you have downloaded base layers!

Deleting Downloaded Base Layers

Your downloaded base layers will remain on your mobile device unless you delete them. To delete downloaded base layers, go to the 3 bar menu in the upper left hand corner of the map viewer. Choose Download Layers from the menu that appears. The Download Layers screen will open again.

To view where you have coverage for particular base layers, please follow the instructions described in Step 2 View Base Layer Coverage for an Area above.

Click on the quadrants you wish to delete layers from. The selected quadrants will be outlined in yellow. Then select Delete from the upper lefthand corner.

iOS Delete Icon Android Delete Icon

The Delete Tiles screen will appear with all the base layers currently downloaded for the selected quadrants. Select the base layer(s) you wish to delete from the selected quadrants.

Select Delete at the bottom of the screen. The Download Layers screen will open again with the quadrants will no longer be shaded blue or purple for the deleted base layers.

Recent Discussions

20 Oct, 2020 02:39 AM
19 Oct, 2020 11:35 PM
19 Oct, 2020 07:09 PM
19 Oct, 2020 05:16 PM
19 Oct, 2020 04:51 AM