This week I have been out doing a little geophysics job and one particular experience from this week inspired me to write this post.
Things were as such going smoothly with our fieldwork, it looked as if we might even be able to pretty much finish two days work in one long day, we were slowly moving south with the stuff we were doing. Then it was that I saw something that made me right away forget about getting this job done in one day ... rape ... about the hight of my head and entangled as only rape can be. We were able to move all measurements but one with the first method we were doing in the area out of the area with rape but had to take some serious detours and the one measurement we had to do in rape took about 3 times the time that one would otherwise do in not so annoying crops.
The next day we were also moving through the same rape, giving us quite a few problems also but this time we were doing PACES which involves a puller on crawler tracks which cleared a way through the lines we were moving on, still the part of the lines that were through the rape did take something like double the time and the measurements were of much worse quality due to the rape lying down were making the earth contact worse.
So I by now really understand why anyone who is just a little experienced in planning geophysics fieldwork try to push the fieldwork so that it can be done when there are as few crops on the fields as possible ... not only because of the problems that the crops (the worst crops here in Denmark being rape, charlock and corn but others can also cause problems). There are times when the job just can't be pushed to the right seasons like the job I did this week ... with the weather we have had here in lately the crops are at least two weeks ahead of what they usually would be.
Again certain kinds of terrain take even more time than any kind of crops, the most extreme experience I have had was when we were lying some CVES lines through a swamp, it took an entire day to get done 1/5 of what we would usually have been able to do on a day.
Other things causing problems is forests, some method just can't be done there (or in "worse" terrain) while others like CVES just takes a lot longer time to do and requires experiences fieldworkers to get good results.
I have been thinking of maybe developing a way of estimating the problems caused by different kinds of crops and terrain for the fieldwork that needs to be done, this would probably be a useful tool for the people put in charge of planning geophysics fieldwork. I have not seen this done anywhere yet, but I would be grateful if someone could point me to such a resource if it exists ... if for not other reason then because it would be interesting to see if my experience from practical fieldwork fits what some theoretic work is predicting.