CARTOGRAPHY since the early decades of the nineteenth
century is characterized by the execution of regular topo-
graphical surveys as national undertakings. Most has been
accomplished in Europe, in some countries of Asia (e.g. India,
Japan, the Dutch East Indies); in the United States and
Canada; and in Egypt and parts of North Africa. Though
similar surveys have been begun elsewhere, progress has not
been rapid, and great areas of the earth's surface are still
unmapped at medium scales on a systematic trigonometrical
framework. For these the cartographer depends upon miscel-
laneous and unco-ordinated material of varying quality,
produced by travellers, boundary commissions, railway and
road development, settlement schemes, and mining and
similar concessions. To these must now be added rapid recon-
naissance surveys, mainly from the air, of considerable areas
carried out during the last war.

The second major advance has been in the enlarged scope
of atlases, and the increasing use of mapping as a technique in
dealing with a wide variety of problems in physical and human
geography, and in administration. This progress was con-
siderably assisted by the change from engraving on copper
plates to colour lithography and its modern developments,
which allow a great variety of detail to be clearly shown.

The great national surveys of the nineteenth century rested
upon methods resembling in general those of the Cassinis.
These were gradually refined as instrumental design pro-
gressed, and corrections were applied to the observations to
allow for factors previously neglected. These included correc-
tions for refraction and the curvature of the earth's surface,
for changes in temperature and other conditions affecting the

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