I'm just starting to get my feet wet after buying the PRO version of RM and have a few questions for everyone.

1. I'm using a Humminbird 899ci with the side scan. When I'm collecting the data, my screen will show the sonar view, down scan view and side scan view. But when I upload the DAT file to RM and use the Sonar Viewer, it only says I can view Channel 1 sonar and the side scan. Why does it not give me an option to view the Down Scan?

2. Is it common to have to manually adjust so many points especially in shallow water? It seems that my unit is recording points pretty well in deep water with some minor adjustments to be made in RM. But in water shallower than 6', it seems the Humminbird is dropping points into the second layer so I'm editing a lot of points. How much manual editing do you do on your collected data?

3. For bottom classification I know E2 gives the best data regarding hardness. When is it appropriate to use the "composite" view?

Thanks in advance for any response!!

Hi PondGuy,

1. The Humminbird SI models don't have a separate channel for down-scan. I believe that they produce their down-scan image by rotating and superimposing the two sidescan channels. Although we did consider emulating this behaviour to produce a "pseudo" down-scan display in RM, we decided against it in the end. The newer ONIX units do have a separate downscan channel, and this is displayed in RM.

2. It's not uncommon in shallow depths, especially with harder bottoms.

3. E2 is the best layer to use for hardness discrimination, but it is very common for users to collect data that doesn't always contain the full second echo return. Composite uses an average of all available return types, and can be useful where some areas have E2 returns and some don't. Using composite lets you use this data as part of the hardness calculations without having empty areas where the data is missing, but if you have good E2 returns then I would stick with that.