 What happens is you have instruments which are similar to cameras on satellites and the satellites are orbiting the earth and all of the satellites which I use are in polar orbits and that means the satellite goes around the poles as the earth rotates and so you see the entire earth in some cases twice a day once in daylight and once at night in other cases where you're looking in much more detail it may take 16 days to lay down all the strips you need around the earth to have complete coverage again during the daytime as well as at night so once you have that information then you have to make sure that you can process those data numerically so they match up to maps and have a high geodetic reference to points on the ground so that if you're looking say at Denver Colorado it's not here one day and somewhere else the next day and somewhere else several days later so that whatever you're measuring is in the same place at every image you have of that area then when you have that information you need to go out and understand what's happening on the ground at a finer scale and this is where field work comes in and I've always enjoyed field work especially if you get to go to unusual places so I've worked all over Africa I've worked in Central Asia I've worked in Mongolia the Amazon basin I've also worked on tropical glaciers in Peru and Bolivia and also Ecuador but you go on the ground make specific measurements in terms of our glacier research we walk around with handheld gpses around the margins of glaciers and record where the actual boundaries are at that time we have satellite data from the same time maybe a few weeks earlier maybe a few weeks later and we combine that information to then set the boundaries of where there's glacier and where there's not and we use that information then over time to refine our analyses and that's what we do and from that you get information about how for example glaciers have varied in their surface area from the 1970s to the 1980s to on the 1990s and now into the 21st century up until this year or perhaps last year