Remote sensing: Aerial photography and Space images

As appears in your book, nowadays, remote sensing is the main technique used for doing maps, and it includes several other techniques as, for example, aerial photographies.
In Spain, the first aerial photos were taken during the 1920s in the area occupied by the rivers Segura by a pilot called Ruiz de Alda, this technique was used also during the civil war, but the flight that covered the area of the entire country were flown by the americans during 1956-57.
Since then, there have been other flights, and nowadays there is a national plan on this topic called PNOA, were you can find the most recent pictures, as well as the oldest pictures taken in the fifties. This plan is carried out by the IGN (Instituto Geográfico Nacional), a spanish organism that collects all the geographical information of our country. (In Great Britain this organisation is called Ordnance Survey).
The space images are the other main method to obtain data from the earth. This pictures are taken by artificial satellites that orbit around the earth. The first pictures date back to the decade of the 1960s, when the first artificial satellites were launched into the space (The first satellite was a russian satellite called Sputnik  in 1957), and the first purpose of these satellite images was a military purpose. But soon this images were used for other civilian purposes, such as doing maps.
These techniques ensure the accuracy of our maps.