I want to map the temperature gradient in my part of town. I live within spitting distance of the lake and want to demonstrate the lake effect. Ideally, I would make the geographical location of reading-taking as a constant (a grid of points across the area) and record the temperature value at that point. i.e. coordinates are fixed, reading is variable. This isn't practical, so what I'm doing instead is making the temperature readings fixed (every one degree change) and letting the coordinates vary, plotting the location on a map. What I'm doing then is normalizing the data. I don't care about the actual temperature , only the change in temperature. I set my house as 0, and normalize all readings from there (+1,+2,+3, etc.) Questions: 1] Say this is my data set for one stretch of road over several days: (+1,+2,+2,+2,+7). So, four of the days this stretch of road is about 1-2 degrees higher than at my house, but one day it was 7 degreees higher. Do I want to take the average(+2.8), or the mean (+2)? Seems to me I want the mean. 2] I'm not sure how I will determine from the data where the contour lines will be drawn. Any point I pick will have only a small portion of readings near it, while the rest I guess I'll have to interpolate? Example: say this is the data on one stretch of road over three days: Code (Text): day 1: +1 +2 +3 +2 day 2: +1 +2 +3 +4 day 3: +2 +3 +4 Arbitrary data point: ^ day 1 interpolated temp: +2.3 day 2 interpolated temp: +4 day 3 interpolated temp: +3.1 Is that right way to go about it? Then, if I take the mean, my temp at this point will be 3.1. Hm. But 3.1 is not where I'll be drawing my contour is it? So now I have to move a little bit left. I guess what I want is the other way around. Where, on those three lines (which could be considered slopes?) is the mean going to be 3? I guess I might end up plotting these on an intermediate graph (x axis=horizontal distance, y axis = temperature). I'd figure out where the middle line (the mean) crosses y=3, and drop that to the x-axis to deterrmone where my contour goes on the road. Advice?