The Imagery Viewer application can be called directly from other applications or users by forming a custom URL string.
The following documentation describes the querystring parameters and their arguments.

To set imagery collection to be displayed, use the ImageryCollection querystring parameter and one of the listed arguments:

    ImageryCollection=[NAIP,PAMAP,DOQQ,DRG,Ivan]

To set the map display to a specific map scale, use the Scale querystring parameter and the denomenator of the scale fraction as its argument:

    Scale=[scale fraction denomenator]

To set the map extent around a specific location or area, use the LocationType querystring parameter and one of the listed arguments:

    LocationType=[County,Municipality,LatLon,ZipCode,MBR,Address]

    Each of the LocationType parameters requires additional querystring parameters, which are described below:

      LocationType=County,CountyName=[name of county]
      LocationType=Municipality,CountyName=[name of county],MunicipalityName=[name of municipality]
      LocationType=ZipCode,ZipCode5Digit=[5 digit zip code number]
      LocationType=LatLon,Latitude=[latitude in decimal degrees],Longitude=[longitude in decimal degrees]
      LocationType=MBR,Xmin=[longitude of west bound in decimal degrees],Xmax=[longitude of east bound in decimal degrees],Ymin=[latitude of south bound in decimal degrees],Ymax=[latitude of north bound in decimal degrees]
      LocationType=Address,StreetAddress=[number and street address],ZipCode5Digit=[5 digit zip code containing street address]
      LocationType=Quadrangle,QuadName=[USGS quadrangle name]
      LocationType=SchoolDistrict,SchoolDistrictName=[school district name]

Examples:
http://maps.pasda.psu.edu/website/Imagery_Viewer/Viewer.asp?ImageryCollection=PAMAP&LocationType=County&CountyName=Luzerne http://maps.pasda.psu.edu/website/Imagery_Viewer/Viewer.asp?ImageryCollection=DRG&LocationType=LatLon&Latitude=40.71&Longitude=-77&Scale=24000 http://maps.pasda.psu.edu/website/Imagery_Viewer/Viewer.asp?ImageryCollection=NAIP&LocationType=Municipality&CountyName=Centre&MunicipalityName=State College http://maps.pasda.psu.edu/website/Imagery_Viewer/Viewer.asp?ImageryCollection=NAIP&LocationType=MBR&Xmin=-78&Xmax=-77&Ymin=40&Ymax=41 http://maps.pasda.psu.edu/website/Imagery_Viewer/Viewer.asp?ImageryCollection=DOQQ&LocationType=Address&StreetAddress=2000 East College Avenue&ZipCode5Digit=16801&Scale=2400 http://maps.pasda.psu.edu/website/Imagery_Viewer/Viewer.asp?ImageryCollection=DRG&LocationType=Quadrangle&QuadName=Harrisburg West