interpolating longitudes from latitude

I have a bunch of lattitudes and longitudes that make up a specific shape with some latitudes and longitudes being repeated.

I need to find a way to interpolate what latitudes would be at a given lattitude point from 40.5-43.5 every .1 interval. My actual data is much more specific with few lattitude points actually at simple numbers and most looking like this: 43.2930.

Is it possible to get this information from my dataset of 536x2 lat and long?

I have tried sorting my data: sorteddata=sortrows(data,[1,2]);

to be able to use: newlon=intrplon(sorteddata(:,1), sorteddata(:,2), 40.5)

but it won't go through I assume since I have multiples of both lat and long.

It keeps giving me this error: Error using intrplon (line 61)

LATITUDE must be monotonic.

Any advice would be great, thank you.

Answer 1

[Sujay C Sharma]

Hi,

The polyfit and polyval functions may be able to help you out in this regard. Here is an example of how you can use it for interpolation:

X = [1:10];
Y = [1:10];
c = polyfit(X,Y,1);
Input = [10:0.1:11];
Output = polyval(c,Input);
disp(Output);

Your latitudes and longitudes from your dataset can be used in place of X and Y and your Input would be [40.5:0.1:43.5] in your case. Do take a look at the documentation of polyfit and polyval for more examples