A Modest Observer of the Mundane. Where do people sit in a park? Where do they talk on a busy street? Ask William Whyte. CITY LIFE

AS the early morning sunlight hits the pastel, Art Deco fa,cades of Ocean Drive, William H. Whyte is already scurrying about the street with his camera, recording the scale of sidewalks, streets, entries, and setbacks. An unpretentious man with a long, bookish face and wispy, white hair, he wears on this particular morning blue suspenders, a red silk handkerchief in his blazer pocket, and an absorbed demeanor. No common tourist, Mr. Whyte is a modest and tireless observer of the mundane.

This self-described ``amateur sociologist,'' who illuminated the way of work and life of a generation in his book ``The Organization Man'' in 1956, has spent the past 16 years observing and recording the street life of cities.

A New Yorker, he will speak later in the day before local television cameras at a hearing on a Miami Beach zoning plan that calls for large new hotels abutting the small-scale historical district.

He finds it ``a very bad plan'' that would rob the neighborhood of valuable sunlight. But he is not surprised. His work has made him a veteran at gently browbeating urban planners and developers over the dynamics of city life.

Whyte's observations are simple and, for the most part, not the least bit philosophical. They are the result of tedious time-lapse photography, steady observation, and mapmaking of such minutiae as where people sit in a park or plaza, where they stand to talk on a busy sidewalk, and at which parks people most often smile in passing. He counts how many pedestrians must tread a sidewalk per hour to sustain a successful retail district (1,000) and the effect of street vendors on nearby restaurants (positive).

But he is also a true believer in the social importance of the city center and the street. In his new book ``City: Rediscovering the Center'' (New York: Doubleday, $24.95), he describes the street as ``the river of life of the city, the place where we come together, the pathway to the center.''

His findings argue against trends now at work in city life, namely suburbanization. For people and businesses to move to the suburbs is one thing. But Whyte sees the worst, most self-defeating trend in the urban designs that try to bring the suburbs to the city, that pull people off the streets and into skyway concourses, underground malls, and closed-off indoor centers, sapping and sterilizing the vital and chaotic public life of the city.

``Cities for people who do not like cities are the worst of two worlds,'' he writes.

``New York City can be miserable,'' he admits, noting that crack cocaine and recent tax assessments have made it worse. ``We pay through the nose for the social ills of New York.'' For these reasons and others, people will continue to flee the central city, he predicts, and corporations will continue to send branch operations into the suburbs.

``But the boss will be there'' in the downtown office, he says, and so will the communications staff and the international division. Likewise, small businesses that create the most jobs will continue to hew to the city center, where support services are at hand.

``I'm optimistic,'' says Whyte. ``The city is going to lurch from one crisis to another. It has always been that way. But that's no reason to despair.''

Whyte's most famous work, ``The Organization Man,'' was based on his study of rootless corporate identities in Forest Park, Ill., near Chicago. That study, he says, ``was concerned with a lot of large, woozy questions.'' He found the interviews exhausting, and they left him feeling inadequate. For relief he made a more mundane study of interactions in local housing courtyards full of young families. He observed and mapped social contacts.

He found, contrary to conventional wisdom, that community leaders usually arose from the courts that made the fewest social demands, where social life was least active. He also began honing his methods of direct observation.

``You do what you like to do. Then you figure out a good reason for doing it,'' he says. ``I've always loved observation.''

His projects have been funded with various grants over the years, including an ``expedition grant'' from the National Geographic Society.

Some of his findings have been mildly surprising: Large cities are friendlier than small cities, inasmuch as the smaller cities show ``fewer interchanges, fewer prolonged goodbyes, fewer street conferences....'' Street conversations migrate - not into quiet eddies out of the sidewalk flow, but directly into the thick of the heaviest flow. Foot traffic congestion is usually a self-regulating non-problem; people gravitate to where other people are.

Whyte's greatest demons are buildings with blank walls at street level - deadening to street activity - and shopping areas designed as fortresses against the spontaneity of the street.

`LOOK what it has done to Charlotte,'' he says of the North Carolina city where the poor wait on the bleak sidewalks for buses, while the affluent crowd the web of skyway concourses overhead. ``You can't measure that,'' he says. ``Look how it has divided that city.''

Whyte helped draft New York City's comprehensive plan in 1969 and has helped to shape urban planning regulations in New York and elsewhere since. Based partly on his research, for example, the city requires retail spaces and see-through glass on the street frontage of buildings.

Cities are far too supine in making demands on builders for sunlight, public space, or friendly sidewalk frontage, says Whyte. ``What you don't ask for, you don't get. You've got to be very specific about what you want. Developers don't mind that.''

The best developers, the Rouse Company, for example, pioneer ways to enliven central cities, and the vitality pays for retail shops there, he says. More often, developers seek to avoid street activity, viewing it as an attraction for undesirables.

``I don't think it's a bad time, to tell you the truth. We're sort of in a trough. There's no blazing idea that everyone's excited about, no Utopian vision.'' And that, he adds, is probably healthy.