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Discussion Starter #1
Since the lat-longs listed on the Chatfield Fish-n-Map are significantly off, I have taken a hi-res image of the Fish-n-Map and superimposed it onto Google Earth view of the reservoir. With the overlay (transparent) I can create more accurate lat-longs of the reservoir structures. So if anyone would like some of the corrected lat-longs of the 40+ structure points, send me a private message of the location number and I will PM back the lat-longs.
 

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I mapped the whole lake using Dr. Depth about 3 years back. I was amazed at how far off the Fish-N-Map lat-lon coordinates were.
 

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Hey Don,
Did you find any consistency in how much the lat-logs were off -- I am finding that the actual structures are 30-40 yards to the south-east (roughly)...
 

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Hey Don,
Did you find any consistency in how much the lat-logs were off -- I am finding that the actual structures are 30-40 yards to the south-east (roughly)...
No, I didn't find any consistency. Here's the analysis I did back in May of 2010:

The Chatfield Fish-N-Map has 47 waypoints. The coordinates for number 46 are seriously flawed so I didn't try to use it. Of the other 46 waypoints, for 28 of them, you could tell what the waypoint was supposed to mark (e.g., top of a hump, top of a small ridge, road intersection, bridge, etc.). With the other 18 of them you couldn't tell exactly where they supposed to be, so I didn't try to analyze them. Of the 28 that I could analyze, 1 marked exactly what it should have, so the paper map and the Dr. Depth map agreed. Another was only 13 feet off and another only 28 feet off, both perfectly acceptable. Four more were 35-50 feet off. The other 21, however, were off by anywhere from 76 feet (25 yards) to 337 feet (112 yds). Those errors are big enough that without a good sonar you would have some difficulty finding the structure to fish it, and it would be especially difficult trying to find it to ice fish it.

The average error for all 28 was 126 feet, and the direction of error was not consistent. Some waypoints were NE of the feature they were supposed to mark, some SE, some W, some SW, some NNE, etc. There was no pattern.

Yes, there is some judgment involved in an analysis like this, but I tried to do it as objectively as possible.
 

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You did a lot of work Don... Will be working on remapping so of the structure this spring.
I had help. Zman recorded part of the data. It was a lot of hours, miles, and boat fuel.

And then I moved across the state and may never fish Chatfield again. :D
 
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