|Without remote sensing
||With remote sensing
|Covering a large area on foot, by car, by boat or even by airplane is very expensive and can take a long time. By the time a large area is covered using these methods, things at the beginning of the survey could have changed.
||A satellite scans a very large area within seconds.
|A survey of a large area of forest, agricultural land, cities or oceans could require paying a team of people and perhaps renting boats or airplanes, potentially making it very expensive for just one project.
||The cost of building, launching, and operating a satellite is shared by the many thousands of people who buy images for their own projects.
|It is sometimes hard to see small changes and it is very difficult to count and record many small changes, especially if they occur over a large area. In order to make good decisions about how to help our environment, we need to know accurately, what is happening where and when.
||A satellite can acquire repeated views of the same area and computers can accurately show what has changed between acquisitions. When dealing with fast-changing disasters (forest fires, floods) or when looking at the slow change of crops, forests or city growth, remote sensing images can't be beaten.
|There is always a lot of guesswork. Resource managers go to a site to take samples or make a count in only a small portion of the area to be studied. Using this information, predictions are made for the entire area. The same survey done twice could produce very different results.
||Remote sensing tells us exactly what is there, how many and where. It doesn't rely on a person's memory or experience. It gives us reliable and repeatable information with measurable accuracy.
|If information is described in writing or even in a drawing, it can be used only in a limited way. It is very difficult to make comparisons to other similar descriptions and it is even more difficult to analyze. It may not be possible to make good decisions based on this type of information.
||Remote sensing information is mostly digital and therefore can be analyzed by computer, compared, and statistics can be collected from it. Decisions can be made more accurately from this type of data.