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I am trying to compare 3 interpolated lines to analyze sediment movement after beach nourishment. Two of the lines start at the same point, but a the 3rd one starts farther inland. However, when I put them all in a graph they are all shown starting at the same point.

Is there a way I can fix this problem?

I tried editing the graph properties and it doesn/t work. All shapefiles and DEM are in the same TX state plane projection. I can't think of any other reason why they would plot correctly. [X axis distance/Y axis elevation, both in ft. Pink and yellow lines in the graphs should start at about 125 ft.][1]

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    The Profile Graph is based only on the 'length' of the segment being profiled. Whether they start at the same point, or at different points is irrelevant. – JasonInVegas Oct 6 '16 at 20:42
  • Quick question: are each of the profiles using different DEMs ? (for example DEMs from different dates?) – JasonInVegas Oct 6 '16 at 20:45
  • Yes, because they where survey in different points in time, every line has a difference DEM. – Naomy P. Oct 6 '16 at 20:46
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If the three different colored cross-section lines are intended to compare profile differences across different DEMs, then the simple answer is to use a single (longest) line segment (the blue one) and create the graph by Profiling the same cross-section across three differing DEMs.

This will ensure that all the profiles are the same length, and that the area of comparison appears at the same stationing on all three profiles. -- of course the profiles can be three different colors, so as to highlight the differences (ie before-during-after or oldest-to-youngest observations.)

To bring attention to just the differences, perform the Profile Graph operations whatever order is necessary to make the blue profile line appear overposted on top of the other lines...that way, the yellow and pink profiles will show only when different from the blue one.

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CHANGE DETECTION. This will require you to compare same spot(location) on the same image(same resolution e.g. if google images, it should be all google images) at different times. For example, you can get Google image of the area at 2004,2005, and 2006 from "history images in google earth". Then you can interpolate line at the same sot and draw it's profile. Then you spot the difference from the DEM from 2004 to 2005, from 2005 to 2006. It will be prudent to get more history images of the same spot and compare DEM to give a strong foundation to your qualitative theory for what is happening at the location.

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  • Thanks you, all! I ended up exporting the graph to .csv and plotting it in Excel. There, I was able to add a constant distance to each station/transect and plot them in the right location. – Naomy P. Oct 13 '16 at 13:45
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Thanks you, all! I ended up exporting the graph to .csv and plotting it in Excel. There, I was able to add a constant distance to each station/transect and plot them in the right location.

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