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About Amending MSA/CMSA Selection
The Amend MSA/CMSA Selection page lets you alter a MSA or CMSA geographic selection by adding and dropping counties.
A metropolitan statistical area (MSA) or consolidated metropolitan statistical area (CMSA) is composed of one or more counties. After you have selected a MSA or CMSA as the geographic area for an AirData report or map, the Amend MSA/CMSA Selection Web page lets you add surrounding counties to the geographic area, and omit counties within the MSA or CMSA.
AirData reclassifies the resulting geographic area as a collection of counties, rather than a MSA or CMSA. The reclassification is significant because a different set of reports and maps is available for a collection of counties than is available for a MSA. Furthermore, the name of the originally selected MSA or CMSA is not displayed as the geographic area name in reports and maps.
How to add or drop counties
The Amend MSA/CMSA Selection page has two lists of county names: those within the MSA or CMSA, and those around it. To add or drop counties, you select or unselect counties in the lists. (The How to Select... page explains how to select multiple items in a list.)
To drop counties within the MSA/CMSA, unselect their names in the first list. Every county in this list is selected initially.
To add counties around the MSA/CMSA, select their names in the second list. No county in this list is selected initially.
At most, you may select 50 counties (or all counties listed, if fewer than 50). The number of counties in each list is displayed in parentheses after the list heading. You must select at least one county.
After choosing the counties you want, click the Select Counties button. Then your browser will display a list of the AirData reports and maps available - those compatible with county geographic area type.
To restore initial county selections, click the Reset button.
Notes
Counties within a MSA/CMSA
AirData uses the 1999 definition of MSAs and CMSAs, as published by
the U.S.
Census Bureau.
In New England states, MSAs are composed of cities and towns rather
than counties. Parts of counties, rather than entire counties, are within
these MSAs. (The partial counties have "(part)" following
their names in the counties-within-MSA selection list.) AirData reports
and maps include whole counties. If the formal MSA definition
includes only a small part of a county, the entire county is considered
to be within a MSA for AirData reports and maps.
Counties around a MSA/CMSA
Counties within approximately 50 kilometers of a MSA or CMSA are included in the "around" list. These counties are chosen by expanding the latitude-longitude bounding rectangle of the MSA/CMSA by 50 km in each direction, and finding counties whose latitude-longitude bounding rectangles overlap the expanded MSA/CMSA bounding rectangle.