Find 2D intersection in lat lon between curve (rivers) and satellite traces (2D polygon) on a map

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Albert Zurita
Albert Zurita 2022-6-15
评论： Albert Zurita 2022-6-24
Hello, this is an expanded question to the original 1D problem in https://es.mathworks.com/matlabcentral/answers/1740820-find-curve-intersection-points-in-lat-lon-between-rivers-and-satellite-traces-on-a-map
I have a set of (lon,lat) points defining the course of a river. Then I also have a set of (lon, lat) points defining the traces of satellite measurements on-ground. The trace is not 1D, there is a 'left' point and a 'right' point, denoting what woud be in reality a continuous 2D band. In fact both the river and the trace are continuous. I want to find the intersections between the river (a curve) and also the 2D trace. I managed in 1D with the answer of the link above, but not evident in 2D at all. Thank you
PS: I include now included exemplary mat data, with the [lon lat] values of the river, and the [lon lat] values of the satellite trace, defined by the left and right points that define the band/belt extremes. On of the problems I see as well is that close to the poles the bands mix because of the projection effect...
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Jeffrey Clark
Jeffrey Clark 2022-6-17
@Albert Zurita, yes the closer to the poles the more problematic lat-lon. Before realizing you created the case where all riv points were in the trace_1/2 I included a step in my proposed solution to convert lat-lon to a cartesian coordinate system in three dimensions, in this case Earth-Centered Rotated (right) as compared to the lon-lat data (I augmented and reversed columns of the lon-lat of all three files with altitude of zero to do the transform from Lat-Lon-Alt to ECR in the figure on the right):

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回答（1 个）

Bjorn Gustavsson
Bjorn Gustavsson 2022-6-17
If you have a single-pass of the satellite you could check what "river-points" are inside the ground-track with the inpolygon function. Check the help and documentation for illustrating examples. My approach would be to split up the satellite-track into single-pass-segments and search for points inside the ground-track pass-by-pass and collect what I need from each.
HTH
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Albert Zurita
Albert Zurita 2022-6-17
But I think it makes more sense to organize by orbit because the wrap-around would make sense to fasten the code, which at the moment it's not a problem.
On the coordinates the problem with ECEF is that they are 3D coordinates, and it seems a lot easier to work on projected coordinates, with of course the caveats we could encounter...
Bjorn Gustavsson
Bjorn Gustavsson 2022-6-17
Oh, yes, by orbit first. The idea to work with unwrap and ecef would be if you have rivers close to your +180/-180 (or 0-360) cuts. For ecef you could possibly work with the x-y coordinates if you are safely on the northern or southern hemisphere - I guess there the cut-problem would be the equator. But now I'm mainly throwing completely unbaked ideas at you for the possibility that I by stupid luck manage to randomly combine a couple of phrases in the right order...

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