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> August 3, 2006 - Building a Topographic Profile
post Aug 4 2006, 08:28 PM
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Today Christina, Leif and I went up to Kongress to begin building a base map for Leif’s project. He is interested in figuring out what produced a strange channel on the west side of the lake. Quite wide and prominent, this channel is currently above the level of the lake and is considered a wind gap. It does get windy through there, and it separates the Linne Valley from the Kongress Basin. In order to make the map, Leif and Christina had to do some basic topographic profiles. We wanted to figure out where and how steep the slopes were so that we could map them.

We built the map by working a bunch of triangles. Let’s talk for a minute about right triangles. Right triangles have three sides - a height, a length and a hypotenuse. If you know two of those lengths, you can draw in the third, right? The same principal holds for topographic surveying. If you want to know the slope (hypotenuse) you need to know the rise (height) and the run (length). There are several ways to do this. We used the simplest way that required the least equipment.

Leif Using Eye Level
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We measured Leif and found that there is 1.75 meters between the ground and his eye height. He used an eye level that allowed him to look absolutely straight toward the ground upslope, forming a right angle. In this picture you can see Leif forming one side of a triangle with his eye height. Christina would walk up slope until her feet appeared in his eye level. Then they held the tape measure along the horizontal length between them. This gave them the second length. From the 1.75 of Leif’s eye height and the tape measure length, we could figure out the hypotenuse, or ground slope. Pretty simple yet effective.

Christina Holding Tape Measure
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Survey Triangle
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They were very careful to get the exact bottom of her boots at his level spot. Christina would stand still exactly where Leif told her to, regardless of the conditions. Now, that is friendship!

Standing Right Where She Had To!
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Sometimes the rise was really small for a long distance, and so we had to measure the height dimension with something shorter than Leif! We had a meter stick along so that we could use that to help us. Sometimes the height above the ground was so small that Leif had to lie down on the hard wet ground. What dedication!

Leif Laying on the Ground

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So, along a line of interest, we were able to assemble a series of triangles. I was in charge of writing all the data in a field book, and when Leif got home, he downloaded the data into an excel file to graph the profiles.

We then went to the eastern side of the lake to the outlet stream. The stream cuts through deeply dipping shale, cutting a steep and narrow channel. This did not phase our surveyors, who wanted to get a profile across this precipitous area. Down they went, measuring with triangles the same way, and then up the other side. It was a lot of fun scrambling around today.

Surveying on a Really Steep Slope...
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... And Up the Other Side!
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This area was really beautiful. The rainy day made the moss wet and very pretty.

Moss by the Stream
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Beautiful Area
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Heidi and Al were heading out for a day in the boat to try to find some moorings, so they had gathered the bathymetry devise (also known as the fish finder) to help them find the moorings. This has a GPS so that last year’s waypoints could be located, and a depth sensor to help “see” the moorings.

Heidi and Al Carrying Bathymetry Device
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Bathymetric maps are really neat. Here is one of Kongress. It shows the depth of the water in contour intervals like a topographic map showing mountains and hill. What is the deepest spot on the lake in Meters? How about in feet?

Bathymetric Map of Kongress
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I can’t stop showing you pictures of the ground! It is very beautiful and colorful. This nitrogen loving lichen is a wonderfully bright orange color, and really stands out in the landscape.

Orange Lichen
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We also get to hike along really amazing fossil rich limestone. We all have found wonderful specimens of brachiopods, horn coral, honeycombed coral and many shells. Here is a rock that is typical of the north end of Kongress.

Fossiliferous Limestone

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Beauty in the Wetness
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