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Air Photo Frequently Asked Questions

How can I locate the specific air photos I want?

The Base Map Online Store (BMOS) enables you to search for air photos and other GeoBC products within specified areas of British Columbia.

Most airphoto operations with photocentres for the years 1963 to 2007 can be discovered and ordered as high resolution digital scans using BMOS. If you require airphoto coverage for the years 2008 and 2009, you can access the digital indices on anonymous ftp here.

For airphoto coverage of an area of interest prior to 1963, the historical hardcopy block coverage indices have been scanned and posted to anonymous ftp here. Please refer to the Ordering Historical Airphotos document for guidelines on using the indices and ordering airphotos as high resolution scans through BMOS.

Air Photo Product Page [PDF]

How do I interpret air photo scales?

A photographic scale is basically an expression that indicates that one unit (any unit you wish to use (inches, centimetres, etc.) of distance on an air photo is a representation of a specific number of the same units (inches, centimetres, etc) of actual ground distance. Scales can be expressed as a unit equivalent (e.g., 1 cm = 200 m), a representative fraction (e.g., 1/15,000) or as a ratio (e.g., 1:15,000).

  • Large Scale: A large scale photo (e.g., 1:2,500) means that ground features are at a larger, more detailed size. The area of ground coverage depicted on a large scale photo is less than at a smaller scale.
  • Small Scale: A small scale photo (e.g., 1:60,000) means that ground features are at a smaller, less detailed size. The area of ground coverage that is depicted on a small scale photo is more than at a larger scale.

Are the air photos accessible to the public?

The Air Photo Warehouse (formerly the Air Photo Library) is closed indefinitely until further notice.

How can I tell when an air photo was taken?

If you know the roll number ('BC', 'BCB' or 'BCC' prefix) of a photo, you can find out what year it was taken by looking it up in the Year/Film Roll Correlation Table.

What do the film roll numbers mean?

Film roll numbers are a series of characters assigned by the Branch that uniquely identified a roll of film. For photos taken since 1977 ( black and white) or 1990 (colour) the film roll number consist of ten-character number with a three-digit extension.

Digit Description Example

Camera focal length code:

  • 88 = 88mm
  • 15 = 153mm
  • 30 = 305mm
  • 60 = 610mm
  • etc.
30BCC03045 - 105
3-4 Always "BC" 30BCC03045 - 105

Film type:

  • B = B&W
  • C = Colour
  • D = Digital (beginning in 2006)
30BCC03045 - 105
6-7 Last two digits of the year of photography - e.g. (19)98, (20)03 30BCC03045 - 105
8-10 Sequential film roll number 30BCC03045 - 105
11-13 Frame number. 30BCC03045 - 105

How do I read an air photo index?

Each aerial photograph has a unique number made up of two parts:

  • the roll number: i.e., BC82012 or BCB97003;
  • the frame (photo) number: i.e., 115 or 221

Flight lines, representing the pattern that the aircraft has flown, are superimposed over the base map. Located along the flight lines are the photo centres of each numbered image.

If you are in need of GPS Air Photo Centre Data (ASCII format) or Camera Calibration Reports (TIF format) please click here

Are air photos available in stereo?

Aerial photography is flown so each frame overlaps the previous frame by at least 60%. This over-lapping area, although of the same portion of the ground, has been photographed from two different camera stations (see illustration), providing two different perspectives of that portion of the ground. When two consecutive air photos are used, it is that difference in perspective that allows the viewer to see the image in 3-dimensions, or stereo.

overlap between adjacent frames

Generally stereo pairs are purchased by engineering and resource professionals for mapping and interpretive purposes. Some clients may be interested in a complete - but not necessarily stereo - "picture" of an area. As air photos are taken with at least a 60% overlap between consecutive frames, there is still an overlap between alternate frames. (see illustration)

overlap between alternate frames