Lake mapping cards (also called chartchip cards or SD map cards) store preloaded depth contour data for specific lakes, regions, or countries. They're an alternative to subscription-based chart services, offering offline access to bathymetric data in the format your specific MFD reads. Here's what's available and how to choose.
Major Mapping Platforms
Garmin's freshwater mapping card covering 17,000+ US lakes with 1-foot contour detail on premier lakes. Installs directly in Garmin ECHOMAP and GPSMAP units — no subscription required after purchase.
Navionics+ annual subscription covers both coastal US and freshwater lake charts — compatible with Garmin, Humminbird, Lowrance, and most MFDs via microSD. Includes SonarChart Live (user-generated depth data) and updates.
Humminbird's native mapping cards — optimized for Helix, Solix, and Apex units with shading and depth highlighting features that integrate with the Humminbird interface. Best on Humminbird hardware.
C-MAP's freshwater and coastal mapping cards — strong North American freshwater coverage with 1-foot contours on major lakes. One-time purchase option available (no subscription).
Subscription vs One-Time Purchase
| Option | Cost Model | Best For |
|---|---|---|
| Garmin LakeVü g3 | One-time purchase (~$100–150) | Garmin unit owners who fish the same region |
| Navionics+ | ~$30–50/year subscription | Multi-brand or anglers wanting regular chart updates |
| Humminbird LakeMaster | One-time purchase (~$80–120) | Humminbird unit owners fishing specific states |
| C-MAP Discover | One-time or subscription | Multi-brand users wanting C-MAP's coverage |