For horizontal accuracy maps at publication scales larger than 1:20,000, 90 percent of all well-defined features, with the exception of those unavoidably displaced by exaggerated symbolization, will be located within 1/30 inch (85 mm) of their geographic positions as referred to the map projection; for maps at publication scales of 1:20,000 or smaller, 1/50 inch (50 mm). For vertical accuracy, 90 percent of all contours and elevations interpolated from contours will be accurate within one-half of the basic contour interval. Discrepancies in the accuracy of contours and elevations beyond this tolerance may be decreased by assuming a horizontal displacement within 1/50 inch.

On a map of the earth's surface, a line that marks the limits of a specific area in precise measurements; commonly encloses the map, legend, scale, title, and other information; serves as the (imaginary) link to an adjacent map.

(1) The environment of a subject property that has a direct and immediate effect on value. (2) A geographic area (in which there are typically fewer than several thousand properties) defined for some useful purpose, such as to ensure for later multiple regression modeling that the properties are homogeneous and share important locational characteristics.

A study of the relevant forces that influence property values within the boundaries of a homogeneous area.

A binary variable used in a valuation model to separate the effects on value of distinct neighborhoods.

(1) The income expected from a property, after deduction of allowable expenses. (2) Net annual income is the amount generated by a property after subtracting vacancy and collection loss, adding secondary income, and subtracting all expenses required to maintain the property for its intended use. The expenses include management fees, reserves for replacement, maintenance, property taxes, and insurance, but do not include debt service, reserves for building additions, or income tax.

A factor expressing the relationship between value and net operating income; the reciprocal of the overall rate.

The ratio of net income to total gross income. This ratio can be expressed as a percentage of potential gross income or of effective gross income. Traditionally, the net income ratio is expressed as a percentage of effective gross income, and is used as a comparison unit for income-producing properties.

The area within a building or structure that is actually occupied by an individual tenant. Net leasable area does not include any of the common areas, such as lobbies and restrooms, shared by other tenants.

A lease in which the landlord (lessor) receives a stipulated rent amount and the tenant (lessee) pays all operating expenses and taxes attributable to the property. A net lease produces net income to the lessor.

Annual net income after operating expenses are subtracted from effective gross income. Does not include payments for interest or principal.

The aggregate of the equities representing proprietary interest; the excess of the going-concern value of assets over liabilities to outsiders; in the case of a corporation, the total of paid-in capital and retained earnings; in a sole proprietorship, the owner's capital account; in a partnership, the sum of the partners' capital accounts.

An artificial neural network (ANN) is a collection of mathematical models that emulate some of the observed properties of biological nervous systems and draw on the analogies of adaptive biological learning. An artificial neural network has several key elements: input, processing (calibration), and output. Other names associated with neural networks include: connect-ionism, parallel distributed processing, neuro-computing, natural intelligent systems, and machine learning algorithms.

(1) A use of property that does not comply with the applicable zoning ordinance. (2) Uses that differ noticeably from prevailing uses in a neighborhood are sometimes also referred to as "nonconforming."

In building a rate of return by the summation approach, an appraiser must add in a factor or rate for nonliquidity. This rate compensates the investor for his or her inability to make immediate use of the investment amount. Generally, the longer the holding period for the investment, the higher the nonliquidity rate will be.

A statistic whose interpretation or reliability does not depend on the distribution of the underlying data.

The error reflected in ratio study statistics from all sources other than sampling error. While non sampling error is unavoidable due to the inefficiencies inherent in real property markets, the imperfections of the appraisal process, and the imperfections of conducting ratio studies, all practicable steps must be taken to minimize non sampling error in ratio studies.

A theoretical distribution often approximated in real-world situations. It is symmetrical and bell-shaped; 68 percent of the observations occur within one standard deviation of the mean, and 95 percent within two standard deviations.

A hypothesis that one chooses to accept in the absence of sufficient evidence to the contrary.

In a fractional expression, the number that is divided by some other number (the denominator). For example, 3 is the numerator of the fraction +; 4 is the denominator.