How to create and use a C-MAP Genesis Edge bottom-hardness map layer to catch more and bigger fish

Many anglers “beat the bank” because they have more confidence targeting visible cover. But the fish in those areas get pounded, making them harder to catch. With a C-MAP Genesis Edge bottom-hardness map, however, you can fish the bottom as confidently as you do the bank, targeting offshore structure like hard-to-soft-bottom transitions and the fish-holding sweet spots on humps, reefs, and shoals, etc. This article will teach you how.

Although it’s a great fish-finding tool, StructureScan alone can’t really show you the size and shape of hard-bottom areas like gravel patches, clay slicks and shellbeds. But C-MAP’s Genesis Edge bottom-hardness layer makes such areas stick out like “Fish Here!” signs on your map. It overlays onto your contour lines a color-coded representation* of the size, shape and location of areas of different bottom hardness: dark orange areas show the hardest bottom; a lighter orange indicates the next-hardest bottom; tan is the next-hardest bottom; and pale yellow shows the softest-bottom areas.

Previously, bottom-hardness layers were available only for waterbodies you map yourself. But with a Genesis Edge subscription, you can now get them for hundreds of select waterbodies available for download from Social Map.
When fish are holding on a harder-to-softer-bottom transition that you can see on your map, you can follow its exact shape, keeping your boat a cast away from it, and make every cast right to the strike zone, and no casts into the non-productive water away from it. So while other anglers are casting blindly – making as many casts to dead water as into the strike zone — you’ll have the spot-on-the-spot dialed in, because you can see the size and shape of the key hard-bottom areas on or near key structure and cover.

Genesis Edge users can follow these steps to download a custom or Social Map chart with a bottom-hardness layer to an SD card and use it in a compatible** Lowrance or Simrad sonar/GPS unit on the water.

  1. Insert a blank SD card into your computer’s card-reader slot
    • If your computer does not have an SD-card slot, you will need to purchase an external card reader that plugs into a USB slot on your computer
    • If you are using an HDS Live, Carbon or Gen3, or an Elite unit, you must first insert a MicroSD card into the empty slot in an SD-card adaptor, or use a USB-slot adaptor that will accommodate a microSD card
  2. Log-in to your C-MAP Genesis account at and open your Dashboard
  3. To download a custom chart of a waterbody you mapped yourself, hover your cursor over the “Trips” window on the right-hand side of your Dashboard and click the blue button labeled “Go To Your Trip List.”(To download a community-sourced chart from Social Map, click this link for how-to directions, then proceed to step #14 below)
  4. Click on the trip or merged map for which you wish to create a bottom-hardness map
    • A list of every waterbody on which you have recorded and uploaded a sonar log will be the page/tab to which your C-MAP Genesis dashboard defaults upon loading. This is the “My Uploads” tab (see image below)
      • If you want to make a bottom-hardness layer for your map of a single trip, click the gray, down-pointing arrow located to the left of the name of the waterbody you’re interested in.
        • This will open a drop-down menu of all your individual trips on that waterbody
        • To open the map of any single trip, click the dark-gray button labeled “view trip
      • If you want to make a bottom-hardness layer for one of your a merged maps, first click the light-gray tab labeled “My Merges” at the top of your dashboard.
        • A list will display of every waterbody for which you have merged the sonar logs from multiple trips into a master map
        • Click the gray, down-pointing arrow located to the left of the name of the waterbody you’re interested in
          • This will open a drop-down menu of all the merged maps you made of that waterbody (see image below)
          • To open a merged map, click the dark-gray button labeled “view trip”
            • Note: If you’ve made multiple merged maps for a particular waterbody, you can determine which one is which by clicking the small images of the waterbody on the left-hand side of the drop-down list
              • Clicking a thumbnail will open a window that displays the individual track lines that are mapped out in the merge
  5. After your map loads, click the “Map Generation” tab (5th tab from left) at the top of your dashboard window (see image below)
  6. In the “Target Device” drop-down menu (located under “Map Options” in the middle of the page), select the Lowrance or Simrad sonar/GPS unit in which you will use your downloaded map
    • Haven’t registered your sonar/GPS sonar units (AKA “chartplotters,” “MFDs,” “plotters”) yet? Click HERE for step-by-step instructions. You can register as many as four separate units. (See image below)IMG_2313
  7. In the “Include Layer” drop-down menu (located under “Target Device”) choose “Composition and Contours” (see image below).IMG_2314
  8. After making all your selections in the drop-downs explained above, click the light-gray button labeled “Generate” (see image below).IMG_2316
  9. Next, click the gray button marked “Download Map.”
    • While the map file is downloading, you’ll see a rotating progress icon floating in the middle of your dashboard.
  10. Once the progress icon stops rotating, you will get the message “Successfully Generated Map! CLICK ‘SAVE’” … below that message will be a light-gray button labeled “Save” …  Click that button.
  11. If you’re using a PC: After clicking “Save,” a box will open allowing you to choose where you want to save the file
    • Choose “SD (D:)” — you’ll see it listed under “Computer” in a vertical menu of options to the left-hand side of the window that opened (see image below)IMG_2184
    • Type in the name of the waterbody and, if applicable, what additional layer it contains, like this: “Long_Lake-with-bottom_hardness.exe”
      • Don’t make any changes in the next field, “Save as type” — leave it as is
    • Click the “Save” button
    • If your web browser is Chrome (which we recommend) you will most likely see, in the bottom left-hand corner of your dashboard, a small, red circle with a white dash in it, next to a message like this: “Long_Lake-with-bottom_hardness.exe is not commony downloaded and could be dangerous”
      • To the right of that will be a white button labeled “Discard” — do NOT click that button
        • To the right of that “Discard” button will be a small down-pointing arrow. Click it to open a dropdown then hover down to and click the word “Keep” … proceed now to Step #13 below
  12. If you’re using a Mac: As soon as you click “Save File,” a compressed/zipped folder containing your map files will download to a pre-ordained spot on your computer, most likely your “Downloads” folder
    • If you have not manually re-set your downloads to be saved somewhere else, it’s going to be in your “Downloads” folder
      • The folder that downloads WILL NOT display the name of the waterbody — it will be named like this: “ (the code will be different for every waterbody)
        • You should re-name that folder now with the name of the waterbody and, if applicable, what additional layer it contains, like this: “”
  13. Before your map files will work in the Lowrance or Simrad sonar/GPS unit(s) on your boat, you must first extract the files (PC terminology) from the downloaded .exe folder/file or unzip the folder (Mac terminology) in which the map files are located.
    • Depending on what kind of computer you are using, follow the PC-file-extraction or Mac-file-unzipping directions at the bottom of this page and then proceed to step #14 below
  14. Remove your SD card from your computer’s SD-card slot (or external card reader)
  15. Insert your SD card into a card slot on your Lowrance or Simrad sonar/GPS unit while the unit is turned off
    • If you have a unit with two card slots, it does not matter if you use the top or bottom, or right or left slot
  16. Turn on your sonar/GPS unit
  17. Soon after your unit powers up, a dialog box will open and ask if you want to load the map that you saved onto your SD card — it will reference the waterbody by name
    • On a HDS Gen2 Touch unit or on an HDS Gen3 unit, simply touch the button that is labeled “Yes”
    • On non-Touch Gen 2 units and Elite units, press the appropriately pointed arrow on the circular keypad in order to move your cursor to “Yes”
  18. Once “Yes” is highlighted, click the button labeled “Enter”
  19. Your map — including the bottom-hardness layer — will then almost immediately load onto your unit’s map-display screen
    • Your contour lines will be visible through the bottom-hardness layer, so it will be easy to see at what depth the transition areas are located
    • You may, from time to time, want to temporarily turn off the bottom-hardness layer and display only your blue-scale contours. Here’s how:
      1. Open the “Menu” drop-down on your “Chart” page
      2. Select “Chart Options” (as shown in image below)01 Select Chart Options-HDS
      3. Select “View” (as shown in the image below)02 Select View-HDS
      4. Select “Categories” (as shown in the image below)03 Select Categories-HDS
      5. A new window, titled “Chart Categories” will open. You will see a vertical list of (at least) four categories, with a check-mark box to the right of each. Following are the four categories you will most likely see (see image below):04 (AREA) Bottom Composition -HDS
        • (AREA) Vegetation & Bottom Composition – This layer will show your bottom-hardness layer (OR, your submerged-vegetation layer, if instead you chosev “Vegetation and Contours” in Step 8
          • NOTE: On a non-touch HDS Gen2, you must press your “Enter” button to click, or un-click, the check-box. On an HDS Gen2 Touch and on HDS Live, Carbon and Gen3 units, simply touch the box with your finger to check, or un-check, it
          • Want to display a grass/vegetation layer AND a bottom-hardness layer on your map at the same time? You can! We’ll document the steps to do so in an ensuing blog post.
        • (AREA) Nautical – Do not un-check this box
        • (LINE) Nautical – Do not un-check this box
        • (POINT) Nautical – Do not un-check this box
      1. After un-checking the “Bottom Composition” box, click the circled X in the upper right-hand corner of the “Chart Categories” window
        • On HDS Live, Carbon, Gen3 and Gen2 Touch units
          • On a non-touch HDS Gen2 unit, push the “Exit” button
      2. When you want to turn the bottom-hardness layer back on, repeat the steps above, but instead of un-checking the “Bottom Composition” box, check it
  20. Study your map and pilot you boat to the bottom-hardness transition area that you’d like to fish

PC instructions

If your computer is a PC, follow these steps to extract your map files from the .exe file/folder you downloaded and saved to blank SD card

  1. Double-click the .exe file that you downloaded/saved to the blank SD card in your (D:) drive
  2. After double-clicking, a dialog box will open — just click the “Enter” button on your keyboard (or, you could click the “Extract” button), and your map files will extract and save themselves onto your SD card
    • A total of five (5) additional files will extract and save onto your SD card. In addition to the original file you downloaded (the one with the .exe extension), you will see new files labeled exactly like this (depending on whether you use a Lowrance HDS or Elite unit):
      • at5.xml
      • permits.txt
      • HDS_Large.at5 (or Elite_Large.at5)
      • HDS_Medium.at5 (or Elite_Medium.at5)
      • HDS_Small.at5 (or Elite_Small.at5)
    • ALL 5 of those files must be on your SD card for your map to display on your sonar/GPS unit.
  3. At this time, we recommend creating a new folder on your computer, naming it “Lake Map Downloads” (or similar) and then dragging the .exe file off of your SD card and into that folder.
    • The .exe file is not necessary to display the maps once the file map files are extracted from it
    • However, it’s a good idea to save the original .exe file for each map you download
      • Because if you should ever misplace the card onto which you saved the five map files detailed above, you can re-extract those files back onto another SD card at a later date, without having to download a fresh .exe file
    • This is an especially important back-up process if you are traveling to fish in a remote area in which you will not have Internet/wifi access
  4. Proceed to Step #14 above
Mac Instructions

If your computer is a Mac, follow these steps to unzip the folder you downloaded and access your map files:

  1. Depending on your Mac’s operating system, your map’s file folder might un-zip itself while downloading. If it doesn’t, proceed to step #2
  2. Double-click the zipped folder
  3. A progress bar will briefly appear on your screen as the folder un-zips. Once that progress bar disappears, your unzipped folder will appear in the same folder that the zipped folder is located (in most cases, your “Downloads” folder, as explained above previously)
  4. After making sure your SD card is inserted into your computer’s SD-card slot (or external card reader) find the icon for your SD card on your desktop and drag the five files in your unzipped folder onto your SD card
    • Rather than dragging and dropping, you could also copy and paste the five files in your folder onto your SD card.
    • The five files should be labeled exactly like this (depending on whether you use a Lowrance HDS or Elite unit):
      • at5.xml
      • permits.txt
      • HDS_Large.at5 (or Elite_Large.at5)
      • HDS_Medium.at5 (or Elite_Medium.at5)
      • HDS_Small.at5 (or Elite_Small.at5)
  5. Proceed to Step #14 above

* This layer will display only in areas in which boat speed, while logging sonar, was slower than 10 mph

** To use C-MAP Genesis maps on the water, you’ll need a compatible Lowrance, Simrad or B&G chartplotter.

2 thoughts on “How to create and use a C-MAP Genesis Edge bottom-hardness map layer to catch more and bigger fish

  1. What am I doing wrong. I have a Hook2. Ive downloaded my lake map to a SD card with all 5 essential files. I made sure my serial number is correct. Ive made sure my content ID is correct and capital sensitive. No matter what I do my download is not being recognized. Are Hook2 5s not able to download custom maps?

    1. Hi Jason: a couple of things to check. First, is your Hook2 running the latest software? Check here – Next, is there an issue with your SD card? Is the Hook2 recognizing it at all? Check files or storage and see if your card is listed. Is it 32 GB or less? Lowrance units will not recognize cards bigger than 32 GB. If none of these fixes work, email and we will investigate further. Include the lake name and location in your request as well so we can investigate whether it might be an issue with that particular map.

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