Sympo 
Hydroloi 
Arthur P.Crac 
Carnegie Labor 
ABSTRACT: This 
achieved by th 
present positi 
fields with cu 
expected to be 
near future. 
1 INTRODUCTION 
It is appropri 
Commission of 
I have in mind 
fields which h 
separate but w 
together and vi. 
close together 
mind are on th 
whether for qu 
quantitative p 
hand the use o 
In the past th 
remain separat 
obtained from 
The difference 
the headings ( 
characteristic 
the improved s 
of instruments 
space, namely 
LANDSAT-5 and 
gap between th 
graphs and tha 
becoming very 
A great deal 
work has, in t 
I might call d 
the land, as d 
the land in wh 
secondary. A 
grammetry has 
graphs it has 
to dealing wit 
Earth. By con 
been based on 
satellite data 
surface of the 
To survey th 
and to assess 
that it is the 
can hardly exp 
relevant chapt 
Manual of Remo 
relevant chapt 
Environment" a 
Assessment"; I 
the main point 
more recent ma 
that edition o 
present positi 
about future d