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much of the character and appearance of the landscape and build-ings. The following aspects of climate can be readily found in UnitedStates Weather Bureau publications.

Temperature: Seasonal temperature and humidity as averages andextremes which indicate the periods of relative comfort, the extremeswhich must be ameliorated, and which therefore determine architec-tural and urban form.

Light: The number of clear, partly cloudy, and fully cloudy days,which conditions the light affecting the appearance of the city and ofbuildings.

Precipitation: The amount of precipitation in the form of rain andsnow.

Sun: The angles of the sun in different seasons, which affectsviewing conditions and, thus, design. It is useful to make a simplethree-dimensional model to study these angles.

Winds: The prevailing seasonal winds including the directionand intensity of cold winter winds, gentle or severe fall andspring gusts, and cooling summer breezes. These affect designconsiderably.

In addition to these quantitative factors there are a number ofqualitative aspects of climate which are as important in urban design.Some cities are well oriented toward the rising sun or the setting sun.Some cities have forms that derive almost directly from their cli-mates—arcaded cities in the sun, for example, Considerable researchor experimentation might be done to determine how cold winterwinds could be slackened and cooling summer breezes induced. Thequality of light—sharp and clear or cloudy and dull—should be adeterminant in the design of building facades including their degreeof intricacy and their coloring. These are always a matter of artisticconsideration but a careful appraisal of actual conditions can help adecision.

Shape

Every city has a general overall shape. There are several classifi-cations of shape.

Radiocentric: The most frequently found urban form is theradiocentric, a large circle with radial corridors of intense develop-ment emanating from the center.

Rectilinear: A variation on radiocentric form is the rectangle,which usually has two corridors of intense development crossing atthe center. This variant of the radiocentric form is found in smallcities rather than large. It is the radiocentric form with right angles.

Star: A star shape is a radiocentric form with open spaces be-tween the outreaching corridors of development.

Ring: A ring shape is a city built around a large open space. TheSan Francisco Bay is such an open space for the cities of the bayarea. A ring and star may be found in combination, particularlywhere a loop road is built around the outskirts of an expanding me-tropolis.

Linear: The linear shape is usually the result of natural topogra-phy which restricts growth or the result of a transportation spine.Stalingrad in the Soviet Union was planned as a linear city. The mega-lopolis on the East Coast has become a vast metropolitan area with alinear configuration.

Branch: The branch form is a linear spine with connecting arms.Sheet: A vast urban area with little or no articulation.

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Articulated Sheet: The articulated sheet form is accented by oneor more central clusters and several subclusters.

Constellation: The constellation is a series of nearly equal-sizecities in close proximity.

Satellite: The satellite is a constellation of cities around a maincenter.

These classifications of form have definite implications for a city’sfunction. They have advantages and disadvantages related to circula-tion, proximity to open space, and articulation of neighborhoods ordistricts. Further, these classifications may be applied to the city as awhole or to parts of the city, isolated for study, like open spaces orcirculation. The open spaces of a city may be linear or branched; orthey may form a radiocentric pattern. The circulation networks maylikewise be described as one or another shape.

Size and Density

Closely related to a city’s shape is its size, a quantitative aspectwhich can be approached several ways. We first of all think of thephysical extent of a city: so many miles across or so many miles fromcenter to outskirts. We can also describe size in terms of the numberof inhabitants. The relation between size and density is impor-tant, for it indicates the distribution of people and the city’s urbanmassing.

Density can be computed mathematically in several ways: thenumber of people per square mile; the number of houses per acre orsquare mile; or the amount of building floor area in a given section. Itcan also be expressed in terms of automobile population. In 1962Los Angeles, the country’s most auto-oriented city, had 2,220 carsper square mile and Washington, D.C., had 4,100 cars per squaremile. This comes as a surprise to most people. One would think thatthose figures are reversed—which suggests a note of caution in judg-ing aspects of quality from statistics of quantity.

The gross size of a city in terms of its population is also revealing.Classifications according to size alone are quite useful. A basic popu-lation of about 200,000 to 300,000 is necessary to support basic pub-lic cultural facilities. Amsterdam, Holland, with a population of abouta million people, is of the maximum size that can be traversed onfoot by a hearty walker, from center to outskirts.

Unless a city is evenly built-up, studies of density are best madeon separate sectors of a city. Density figures indicate the relationshipbetween built-up and open land; therefore they can describe almostgraphically the image of a suburban residential area or an in-townrow-house area. Densities have definite implications for variousforms of transportation. In making a visual survey, it is helpful todetermine the density of various areas and to relate the density fig-ures to physical patterns of land and buildings and, hence, the visibleform of the area.

Pattern, Grain, and Texture

Urban areas have distinct patterns. Usually these are seen in theirblock and street layouts. Most American cities have rectilinear blockand street patterns. On rolling terrain, in outlying areas, curvilinearstreets and blocks form another type of pattern. A cul-de-sac systemforms a third pattern. Mixtures of open space and built-up space con-stitute still another pattern. A basic design pattern can be very helpful

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in planning a residential area or a campus area. An urban pattern isthe geometry, regular or irregular, formed by routes, open spaces,and buildings.

Grain is the degree of fineness or coarseness in an urban area.Texture is the degree of mixture of fine and coarse elements. A sub-urban area with small houses on small plots has a fine grain and auniform texture. With small houses on varying size lots, it couldstill have a fine grain but an uneven texture. In the city, largeblocks with buildings of varying sizes could be described as hav-ing a coarse and an uneven texture. If the buildings are uniform insize, they could be described as having a coarse grain but a uniformtexture.

Such distinctions are easily indicated on a sketch map. They areuseful in evaluating an area’s form and in making decisions about adesign treatment for it. For example, a coarse-grained unevenlytextured area may be impersonal and repellent and could be treatedwith some fine scale and unifying design elements, An extensiveand uniformly-grained area might well be treated with relievingaccents.

Urban Spaces and Open Spaces

Urban shape, pattern, grain, size, density, and texture are prima-rily aspects of solid form—the building masses of the city, In archi-tecture it is rather helpful to conceive of a building not only as a solidbut as spaces modeled by solids. It is also helpful to consider a citythis way. The spaces of the city range from the space of the street tothe space of a park system and, ultimately, to the vast space in whichan entire city exists. It is helpful to think of these spaces as two ge-neric types: formal or “urban spaces,” usually molded by buildingfacades and the city’s floor; and natural or “open spaces,” which rep-resent nature brought into, and around, the city.

Basically an urban space must be distinguished by a predominantcharacteristic, such as the quality of its enclosure, the quality of itsdetailed treatment or outfittings, and the activity that occurs in it. Anurban space should, ideally, be enclosed by surrounding walls, havea floor which suits its purpose, and have a distinct purpose to serve.If, however, any one of these qualities is sufficiently strong, it alonemay establish the sense of urban space.

A group of office buildings may contain a space around a poorlydesigned plaza or a complex road intersection, the floor space be-ing devoted entirely to traffic. This is an urban space which has asense of place in the city. It is both a landmark and a traffic node, aswell as an office node. An urban square may be beautifully land-scaped as a restful urban park, but it may lack entirely the periph-eral building facades which are needed for a sense of enclosure.Here we have a poorly enclosed space, but a space nevertheless. Inanother instance, a particular place in the city may function as thelocale of an important activity while possessing neither physicalenclosure nor appropriate floor. Times Square in New York is suchan example.

In all these examples we have a sense of space. Such spaces areislands or oases in the city. But urban spaces can also be linear corri-dors. Avenues and streets are linear urban spaces if they are enclosedon two sides or have some element of unifying character—trees oruniform buildings. Corridor spaces are spaces for linear movement.Island or oasis spaces are stopping places. Of course the two can be

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Making a visual survey