Custom Maps app makes it easy to place an image of a map in real-world location, so that you can use it with your Android phone's GPS. It's especially useful if you plan to go someplace where you don't have cell carrier coverage, or if you simply want to use a map with features that Google Maps doesn't have.
A quick tutorial video showing how to use Custom Maps app is available on YouTube: https://youtu.be/qVuQenIzwik
Add a map image to your phone
There are 3 ways to add a map image to your phone:
Using your Android phone, download a map image from the Internet.
Display the map image on your computer monitor, and take a photo of your monitor screen with your phone's camera.
Take a photo of a paper map with your phone's camera.
Please ensure that you have the necessary rights to use the map image before copying, distributing, or using it in Custom Maps.
In this example, we will use the first option: Using your Android phone, download a map image from the Internet.
To download a map image of Point Reyes National Seashore, on the coast of California, US, scan the QR code next to the map image below, or enter this URL (http://www.custommapsapp.com/tutorial) into your Android phone's browser, and touch the map image displayed below.
When you see the large map appear on your phone, touch-and-hold to "Save Image" to your phone. This will download the map image from the Internet onto your phone's storage.
Create a new map
Open the Custom Maps app from you phone's menu.
Press your phone's 'menu' button to see the menu options.
Select "Create map"
Find the map image on your phone.
If you are following this example and downloaded it from the Internet, you will find the map image in your 'download/' folder.
If you took a photo of a map with your phone's camera, you will find the map image in your DCIM/ folder or other location where your phone stores camera photos.
Select the map image file: 'PointReyesNationalSeashore.jpg'
Give your Custom Map a Map Name -- the app automatically enters the name of the image, but you can choose to change the Custom Map's name if you prefer.
Give your map a description (optional).
Then click "Add Point."
Add the first tie point to the map
Move the map so that the center circle falls on a recognizable location on the map image. Then click "Select point."
Next you will see Google Maps, with your transparent map image overlaid on top. Adjust the sliders at the bottom of the phone's screen to line up the map image with Google Maps as close as you can.
Adjust the Transparency of the map image to better see the underlying Google Maps, to assist you in lining up the image.
Adjust the 'Scale' slider to change the scale, or size, of the map image.
Adjust the 'Rotate' slider to rotate the map image. This is especially important if your map image doesn't have the north direction up.
Once you have lined up your map image with Google Maps as best you can (it doesn't have to be too perfect!), click the "Accept" button.
Add a second tie point to the map
Move the map so that the center circle falls on another recognizable location on the map image. Then click "Select point."
Next you will see Google Maps again, with your transparent map image overlaid on top. Line up the map image with Google Maps as close as you can, just as you did for the previous point. For this point, matching only its center point is important.
Click the "Accept" button.
Preview your map
Click on the "Preview" button to preview your new custom map.
Zoom in, and adjust the Transparency slider to preview your alignment. When previewing the map alignment with only two tiepoints, the alignment looks good initially, but closer inspection (after you zoom in), the Northern tip of Point Reyes shows that the road alignment is little off in North-South direction. Similar error is visible throughout the Northern parts of the map.
To perfect your map further, return to point list by pressing your mobile device's "Back" button.
Add a third tie point to the map
Click on the "Add point" button.
Add a third point to line up your map even better. Note that additional points after the first two should never be located close to the imaginary lines connecting the earlier points, as this wouldn't really help with the alignment any further.
Click the "Select point" button.
Save your map
Click the "Preview" button to preview your adjusted map again.
If you are happy with the alignment, click the "Save" button. Your map is saved to your map list.
Share the map with friends
After you load your map, press your mobile device's "Menu" button, and select "Share map"
Enter the email address of your friends, a custom email message if desired, and click "Send" to send the email.