Benefits of New Photography
Aerial photography is one of the primary sources for gathering geo-referenced information. The reliability of that information is a direct result of how current it is. In addition, many projects have specifications which do not precisely match existing photography. If this is the case, the project may actually cost less with new photography.

Options Available When Ordering New Aerial Photography

Before we can quote you a price for a specific project, we will need to have certain information. Some of this can be developed while working with us, but the following list will give you an idea of some questions which will need to be answered.

Analog or Digital
We are now capable of capturing digital aerial images with our new Imacon Ixpress Digital Camera as well as conventional analog images with black and white/colour negative film with our Wild RC 20 camera. Digital vs. Analog.

Project Location
Simple enough - try to be specific.

Project Area
It is best if you can outline your area on a map sheet which can be faxed/mailed/ e-mailed to us. This way we can plot our flight lines to cover the area in the most efficient way possible.

Photo Scale and Ground Sample Distance (GSD)
Ranging from 1:2,000 to 1:44,000 for analog projects and 10cm to 100cm GSD for digital projects, which will be determined by your project requirements and your budget. A larger scale or smaller GSD (ie. 1:2,000 or 20cm) will mean more flight lines and more photos on each flight line - which raises both the cost and level of detail.

Camera Focal Length for Digital and Analog
The digital camera focal length is 60mm, which is suitable for property assessment as well as cutblocks. Digital Orthophotos can be created without the need to scan negative film.

Click on Digital Images to Enlarge:
Schwartz Bay - 1.79Mb	Cutblock - 2.63Mb	BCIT Orthophoto - 2.67Mb

For the analog camera, either the 153mm (6-inch) or 303mm (12-inch) lenses are available. In general the 6-inch lens is required for high accuracy elevation mapping and the 12-inch lens is more suitable for forestry purposes. Most low-level projects (<1:5,000) in mountainous areas must be completed using the 12-inch lens.

Film Type for the analog camera
In general there are four types of aerial films:

• Black-and-white
• Colour
• Black-and-white infrared
• Colour infrared

Selkirk Remote Sensing is experienced in handling any of these films. Black-and-white is the least expensive and may be used under the largest variety of weather conditions. The two infrared films should be used for a specific objective such as looking for standing water or plant health.

Overlap
Forward overlap and side overlap must be specified for each project. (Side overlap is not needed if there is only one line.) Forward overlap is commonly 60% which allows the film to be used for stereoviewing. Another alternative is to use 80% overlap which allows the client to use every second photo in stereo. Additionally, 80% forward overlap is better if the photography is to be used for mosaics (attaching many photos together to make one larger picture). Side overlap is commonly set at 30%, though this can be adjusted to meet specific needs.

Timing of Acquisition
Depending on the project, the timing can be very important or almost completely irrelevant. Some projects which require ground targeting can demand photography during a specific time period such as a certain week - though this is always weather dependent. Other projects may just need to be completed during a longer time period such as the current photo season. When ordering aerial photography please indicate the time-dependency of your project to ensure we meet your needs at the lowest possible price. Aerial photography is dependent on certain sun angle levels to ensure adequate photography. In the Vancouver area, the optimum angles to the sun are available from the beginning of March until the middle of October. These dates must be adjusted slightly at different latitudes and project specifications. These are only guidelines and under certain conditions we may be able to complete your project at any time of year. Please contact us for more information.

GPS for Perspective Centre Recovery
We now have the capability to recover camera station perspective centres to accuracies of up to 15cm RMS. The request for acquisition of this data can be specified in two ways. First, we can record the data and supply you with the GPS perspective centres for a quoted price but you will pay a separately quoted price for the photography - regardless of the GPS quality. Alternatively, the GPS data can be an integral part of the project - if the GPS data is inadequate, we will rephotograph the project as part of the original quote. Please indicate your requirements including what accuracy of data you require.

** At this time, we do not offer camera station perspective centres for the Digital Camera, however, the GPS Log file can be provided if required.**

Film Annotation
We are able to annotate the film with information such as roll number, nominal photo scale, date or other information as requested by the client.

Digital images can be saved according to line number and photo number (i.e. Line4_0010.tif) or to the clients specifications as an 8 or 16 bit image. 16 bit images have a higher resolution but depending on the project, the diffeerence between 8 and 16 bit is visually indistinguishable. Most older software such as ArcView 3.x do not support 16 bit images whereas ArcGIS 8.x does.

Index Maps
Index maps are inked on maps to show the location of the photography. We are now capable of producing maps using ArcGIS and can provide both plotted maps as well as PDF files or digital TIFF images to the client. In general every 5th photo is shown.

Prints, Diapositives and Enlargements
These products may be ordered with the photography or at a later date. Prints and diapositives are 10" x 10" while enlargements can be a variety of sizes. Please see our photo library for a more thorough description of possible products.

Purpose of Photography
Possibly the most important specification relates to the purpose of the photography. The purpose indicates the required quality of photography. While we always strive to acquire high-quality photography, there are many projects which are more constrained by time than quality. This is the case in many mapping projects and volumetric surveys. Projects which are designed for orthophoto purposes or for presentations must generally be acquired under ideal weather conditions.