How Altimetry Charts Work - Fishing Forecast

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Instructor: Thomas Hilton

Altimetry is a crucial data point for offshore fishing trips, revealing upwellings and downwellings in the ocean. Knowing where good upwelling occurs can guide the fishing route. Tom Hilton demonstrates how to use altimetry charts to catch more fish.

Description / Review / Instructor


  • Altimetry Maps: Show wave height differences.
  • Upwelling: Cooler, nutrient-rich waters pushed up from the deep; high in phytoplankton and zooplankton.
  • Food Chain: Squid, bait fish, and larger pelagic species are drawn to upwelling areas.
  • Best Fishing Spots: Edges of upwellings.
  • Downwelling: Opposite of upwelling; nutrients are pulled down causing offshore gamefish to leave.
  • Reading the Imagery: Understand upwelling (nutrient-rich) and downwelling (nutrient-poor) currents.
  • In The Spread Video: Tom Hilton explains how to use altimetry for fishing trips.
  • Hilton’s Realtime Navigator: Satellite mapping for sport fishing.
  • Benefits: Save time & money by locating productive fishing waters.
  • Thomas Hilton's Insight: Altimetry data helps understand upwelling cyclones and downwelling warm core eddies.

Understanding Altimetry in Offshore Fishing

Altimetry, in the context of fishing, is the study of wave height differences on the ocean's surface. These maps or charts serve as invaluable tools to discern areas where the ocean surface may be higher or lower due to various oceanographic phenomena, such as upwelling and downwelling.

Upwelling vs. Downwelling: A Deep Dive

    Upwelling: This is where cooler, nutrient-rich waters rise from the deep. The waters brought to the surface during upwelling events are teeming with phytoplankton and zooplankton. These microscopic organisms are crucial as they form the very base of the marine food chain. Consequently, areas of upwelling attract a diverse range of marine species:

  • Bait fish, such as squid, are drawn to these regions due to the abundance of food.
  • Larger pelagic species then converge to feast on the thriving bait fish populations.
  • The peripheries of these upwelling zones, as depicted on the altimetry maps, are prime fishing spots.

    Downwelling: Contrary to upwelling, downwelling involves the sinking of surface water, carrying with it the rich nutrients. This results in a scarcity of food at the surface, leading offshore gamefish to vacate the area. It's advisable for anglers to avoid fishing in regions with prominent downwelling.

Interpreting Altimetry Maps

Understanding the imagery that distinguishes upwelling (nutrient-rich) currents from downwelling (nutrient-poor) currents is essential. To be successful in offshore fishing, one must discern what the altimetry map conveys.

In a compelling video from In The Spread, Tom Hilton, the brains behind Hilton’s Realtime Navigator (a renowned satellite mapping service for sport fishing), delves into the intricacies of using altimetry to optimize offshore fishing excursions. By tapping into this knowledge, anglers can efficiently pinpoint productive fishing zones, ensuring a more fruitful outing without unnecessary guesswork.

Hilton's service offers a comprehensive view, merging various data points like surface heights, Sea Surface Temperature (SST), chlorophyll concentrations, currents, planned trip routes, and much more.

In the words of Thomas Hilton:

    "Altimetry data captures the upwelling cyclones and downwelling warm core eddies present offshore. In the northern hemisphere, cyclones exhibit a counter-clockwise rotation, ushering nutrients from the ocean floor to the surface. The interaction between plankton and sunlight initiates the primary links in the food chain. This, in turn, attracts bait and subsequently larger game fish. However, every action has an equal and opposite reaction. Warm core eddies descend, drawing everything with them, thus resulting in minimal feeding activity."

To sum it up, understanding and leveraging altimetry can be a game-changer for offshore fishing enthusiasts. It's not just about casting your line; it's about knowing where and when to do it.

Frequently Asked Questions (FAQ)

What are Altimetry Maps?
They are maps that showcase the differences in wave heights. They help to identify areas of upwelling and downwelling.

Why is Upwelling significant?
Upwelling brings cooler, nutrient-rich waters from the deep. These waters are rich in phytoplankton and zooplankton, which are vital for the food chain.

Where should one fish?
The edges of upwelling areas are generally the best to fish, as they attract bait fish and, in turn, larger pelagic species.

What is Downwelling?
Downwelling is the opposite of upwelling. It involves the rich nutrients being pulled down, causing offshore gamefish to leave the area.

How can I read the imagery effectively?
Tom Hilton's video from In The Spread explains how to interpret the imagery on altimetry maps for effective fishing.

What is Hilton's Realtime Navigator?
It's a satellite mapping service designed for sport fishing, which helps users understand where to fish based on various data points.

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