|
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.
Please login for an estimate, or contact
us for a firm quotation.
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 30 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 or Ground Sample Distance (GSD)
Ranging from 1:2,000 to 1:44,000 for analog projects and 10cm to
100cm GSD for digital projects, this 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 two types of aerial films:
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.
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.
|
