Lowrance MapCreate 6 Installation And Operation Instructions Manual page 11

This solid-state, flash memory device is about the size of a postage
stamp. (SDC [Secure Digital] cards are also compatible with any
Lowrance or Eagle product that uses MMCs.)
The MMCs shipped with Lowrance and Eagle GPS units are 16 MB
size. If you're using a 16 MB MMC, your Custom Map File must be less
than 16 MB in order to fit on the card. (This space issue is the same as
floppy disks; you can't really fit a 1.44 MB file onto a 1.44 MB diskette
because some space is required for the disk's file allocation table. In the
case of a 16 MB MMC, actual maximum useable space is about 15.2
MB.)
MMCs and SDCs are used in a variety of other digital devices. Most
electronics or digital camera stores sell MMCs and SDCs, and at press
time they are available in 8 MB, 16 MB, 32 MB, 64 MB, 128 MB and
256 MB sizes. Cards with larger capacities may be available in the
future. MapCreate is a powerful tool for your GPS, because it allows
you to match your map's file size and detail level to your card's memory
capacity and your travel needs.
Other GPS units use direct serial cable connections to transfer high
detail maps from a computer to the GPS device. Lowrance and Eagle
switched from this traditional method to removable memory cards for
several reasons. A USB card reader can transfer a large custom map to
your unit 30 times faster than a serial cable connection. Removable
media means you don't need to have a computer and cable with you to
load a new map in the field. If the unit is mounted in a vehicle, there is
no need to dismount it and carry it to a computer. The effective
mapping memory capacity of your GPS unit is limited only by the
capacity and number of memory cards you want to carry with you. This
is a handy feature for long journeys or for users who can't lug a laptop
computer along.
Four factors control Custom Map File size: 1. map detail level option
settings, 2. the number of map feature categories turned on, 3. the amount
of developed or naturally occurring features in the area and 4. the amount
of territory, that is, the number of square miles or acres in the area.
Detail Level Options can be set high or medium. The higher the
detail, the bigger the file size.
There are dozens of Map Category Options that you can turn off and
on. They include natural features — such as rivers — and man-made
items such as roads, businesses or other Points of Interest. The more
categories and subcategories turned on, the bigger the file size.
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