What is Custom Maps app good for?
Custom Maps can be used at least for the following purposes when suitable maps have been downloaded to or created on the phone. Please ensure that you have the necessary rights before copying, distributing, or using a map image in Custom Maps.
Hiking in state and national parks that are not covered by cell data network. By using a screenshot, download, digital image, or a photo of a park's trail maps, you can create a custom map to track your progress during a hike.
Avoiding roaming charges when traveling abroad. Tourist maps may be accurate enough that they can be turned into digital maps with the app, and used while the phone is in airplane mode to avoid roaming data charges.
Amusement park and zoo maps. If you are visiting an amusement park or a zoo, a digital map can help you find your way around all the attractions in the park.
Custom maps for special events. If you organize a large gathering with multiple activity stations distributed around a large area, you can draw a map of the special locations on top of a printed map and take a photograph of the map. Then you can align the photo over Google Maps to turn it into a digital map with Custom Maps app.
If you come up with other creative ideas for using Custom Maps, let me and everyone else know through mailing list link in the sidebar on the left.
Does Custom Maps send my location information to some servers in the internet?
Custom Maps does not store user location information, and when the app is used to view maps it does not use or need any kind of internet connection. It only needs a GPS signal from satellites. The app uses internet connection only when new maps are being created.
My device fails to open a photo for creating a map. What can I do?
Android limits the size of memory used by any single app. This amount of memory depends on the device and the version of Android. All devices should be able to open images up to 3 megapixels in size, for example 2000x1500. You can check the maximum image size your device can handle on the settings screen inside the Custom Maps app.
Notice that some phones can take photos that are larger than the largest image size Custom Maps app can handle. If that is the case, you can change the camera settings to take 3 megapixel photos, and take another picture to be used for the map.
My friend shared a map with me, but I cannot open it.
It is possible that the map image in the shared map is too large for your device (see previous question). Check the largest map image size supported by your phone in the settings screen, and let your friends know not to share larger maps with you. If you are sharing maps with your friends, it is better to limit the map images to 3 megapixels, so that all devices should be able to open them.
How can I create my own maps?
Read the tutorial for creating maps. The link to the tutorial can be found also on the top of the page throughout this web site. Below is a condensed summary.
It is relatively simple to create your own map using Custom Maps. Just follow these steps.
Ensure that you have the necessary rights to copy and use the map image in Custom Maps before doing so.
Get a map image you want to use. You can either download one from the web, or you can take a photo of a map. Remember that Custom Maps app has limits to the size of images it can use. You can check the estimated maximum image size your device can handle on the preferences screen.
Launch Custom Maps and select "Create map" option in the menu on the "Select map" screen.
Select the image you want to use. If you downloaded a map image from the web, or if you took a photo of a map, you can find menu options that take you directly to the folders where those images are.
Name to your map and optionally add a comment to help you find the map in the map list later.
Press "Add point" button to select a point on the map image, and then find the corresponding point in Google Maps.
Repeat step 5 to match a second point between the map image and Google Maps. It is usually best to use two points at the opposite sides of the map image. You can add more than two points, but the application uses at most four matching points, and there is a good chance that additional matching points will distort the map too much.
Use "Preview" button to evaluate the accuracy of the map you are creating. If the map image seems to match Google Maps imagery well, save the map and it will be available for your use. If you are not happy with the map alignment, you can return back to matching point list with "Back" button and adjust existing matching points or add new ones. Long pressing a point in the list allows you to adjust or delete that point.
Remember that all maps are not drawn exactly to scale, so it may be impossible to align all areas of a map image exactly to Google Maps. You should consider your displayed location on the maps always an approximation of your real location.
Can I use PDF map images for creating map files?
Yes, but you need version 1.5 or later of Custom Maps app, and an Android phone that runs Android version 5.0 (aka Lollipop) or later.
But if you are willing to do a bit of work with the PDF file you can use maps in them with older devices. First you need to open the PDF document containing the map on your computer and save the map page from the PDF as a JPG image file (Preview application on Mac OS X does support this, and some graphics editors allow opening PDF documents as images). Make sure the image size does not exceed the maximum recommended resolution listed on the Preferences page in Custom Maps app. Then you need to transfer the resulting image to your phone's storage, and with the image on your phone you can follow the instructions on the previous question to create a map out of that image.
How many tiepoints are required to align a map image?
Usually two points are enough, and sometimes when the map image is not drawn to scale very well, a third point can make the map fit worse than just two points. On the other hand, well selected four points close to map corners can make a map work better (especially when photographs are used), but not all maps can be aligned. Also, sometimes some features of the map are misaligned worse than others, and sometimes it pays off to remove a tiepoint and replace it with a different one. The program allows adding more than four points, but only the first four points are used by the app. Points can be adjusted or deleted by tapping and holding (aka "long-pressing") a point in the list.
Can I share the maps I have created with Custom Maps?
Yes, Custom Maps includes "Share map" option in the application menu which can be used to send a map to your email contacts. Sending and receiving maps requires naturally a working internet data connection (wifi or cellular data). Do not share maps unless you possess the necessary rights to do so.
I found a .kmz map file in the internet that looks nice. Is there any way I can check if it is properly aligned before I go out and use it?
Yes. When you are selecting the map, "long press" it (hold your finger down on it until a menu pops up) and select "Modify map" from the menu. In the "Modify map" activity you can rename the map or change the associated comment, and in preview screen you will be able to see how well the map lines up with Google Maps data (both road map and satellite). If the alignment does not look good enough for you, you can return back to previous screen and try to adjust the tiepoints used to match map image features with geo-coordinates (and Google Maps). They can be adjusted by long pressing the points in the list. Notice that many map images are not geographically accurate, and cannot be aligned perfectly with reality. They can still be useful as maps showing you the approximate area where you are located. Use your judgement when using Custom Maps.
Why do some maps fail to open with an error message about not enough memory?
Android phones limit the amount of memory each application can use, and large images like maps take a lot of memory to display. All modern Android phones should be able to display map images up to 8-16 megapixels in size, and some of the newer phones with lots of memory and new operating system versions can display map images that are over 24 megapixels in size. If you plan to create a map for sharing with other people, you should consider limiting yourself to map images that no larger than 8 megapixels. You can find out what the largest estimated image size for a specific phone is by opening the Settings page in Custom Maps.
What are .kmz files?
Custom Maps uses .kmz files for storing its maps. They are zip-formatted .kml files that can contain additional resources like images (KML is short for Keyhole Markup Language, named after the company who created the file format). The .kmz files used by Custom Maps app are typically not compressed since jpg and png image files don't typically compress almost at all, and the data files assigning the geographic coordinates to the map images are so small that they don't really benefit from compression. Uncompressed files can also be processed faster by Custom Maps, but it can handle compressed files as well (not password protected .kmz files though).
Should Custom Maps be able to use any .kmz file? I found a .kmz file on the web that I cannot open with it.
Custom Maps can not display all .kmz files. For Custom Maps to be able to open and display a .kmz file, the file must define an image overlay (aka GroundOverlay), and the image must be stored inside the same .kmz file. There are many .kmz and .kml files on the web that either contain no image overlays, or the image overlays specify that the map image is stored somewhere in the web. Since Custom Maps is designed to work offline, it does not even attempt to follow web links. Such kmz and kml files can be displayed usually only with Google Earth application on a desktop computer.
I have created a map from an image I have rights to distribute. I want to post a QR code for others to scan and download it from my web site. What should the QR code contain?
The QR code should contain a URL in format http://www.custommapsapp.com/qr?url=<actual-map-file-url>
For example, the QR code for the sample map of Europe contains this URL: