eTrex 10 Garmin

In the next dialog box you will see a list of Garmin maps, installed on your PC. Since the modern maps size is much greater than the available Garmin Etrex 10 memory, we have a little interest in this list. But? to simplify map downloading into the GPS device, it is important to remove the checkbox in front of each map.
Then click "Advanced / Partial Install ..." for individual map merge from installed tiles.

In the next dialog box first it is necessary to select a map gmapbmap by using the dropdown menu at the bottom of the box. Then, moving the map by the arrows in the upper left of the box and increasing or decreasing the scale by the slider, select the desired region. Clicking the left mouse button on a tile, you will select it for your individual Garmin Etrex 10 map merge. By the right-click you can deselect the tile.
Indicator below the map preview shows the selected tiles size and your GPS device available memory. If it turns red, it means that the merged map card will be larger than Garmin Etrex 10 available memory. Deselect one or more tiles so that the indicator turns green again.

However, for reliable performance and tracks / waypoints recording it is advisable to leave some free space in the GPS device memory, try to keep the map size not greater than 5 - 6 MB

Also you can carry out a quick search of the desired region simply by clicking "Find a city" and entering the name of the nearest city in the pop-up dialog. Further tile selection is produced as it described above.

Then click "Continue" and "Install". Your individually merged map will be sent to your Garmin Etrex 10.

Garmin eTrex 10. Online Help