Question 1: Spline interpolation is recommended by interpolation method. First interpolate the ordinate on each fixed ordinate, and then interpolate the abscissa on each fixed ordinate (including the newly inserted coordinate values). The density of the insertion point is large enough, and the diagram will come out. How big the density is, you need to grasp it yourself. However, it is estimated that the density of one point per 1 meter is definitely enough.

Question 2: There are three methods based on the question 1. Method 1: directly traverse the enumeration. Calculate the development cost from the upper left corner of the rectangular diagram to each point. If the density of points is 1 m, there are about 2 1000 schemes, and the calculation amount is not too large. Method 2: Genetic algorithm (the specific principle is available online, which is not complicated, so I won't repeat it here). Method 3: Because the ground is continuous, the same method as method 1 can be adopted first, but the distance of each translation of the rectangle is 30m, that is, each initial known point is traversed (except for the infeasible). Then, after finding several (say, five) known points with the lowest cost, we can find a better scheme around these points.

Question 3: I don't quite understand the meaning. I guess I want to find two plots of land, each of which is not less than 60*60, and the two plots are connected together. If yes, choose the size of 60*60 first, and the search method is similar to that in question 2.