Posts tagged: CHDK

Vertical Aerial Photography Spreadsheet

By , June 20, 2013 7:39 pm
Flying Around the Peggy's Cove Lighthouse

Flying Around the Peggy's Cove Lighthouse

One of my favorite hobbies is taking aerial photographs using a model airplane. It's a challenging hobby that is rewarding when you capture "the perfect photo" from a unique vantage point.

I live in West Dover, Nova Scotia which is a coastal area known for its rocky unforgiving landscape with exposed granite boulders. This meant I needed to find a rugged aerial platform as the basis for my aerial photography activities.

My brother and I started our aerial photography experiments back in 1999 with kite aerial photography (KAP) using large homemade tetrahedral kites and a remote control camera platform. Over the next decade we slowly switched our aerial photography projects to a flexible ripstop nylon Sutton Flowform kite, and then onto numerous model airplanes and advanced electronics hardware searching for the right gear.

These days I've settled on using a Multiplex Easystar plane with a Canon Powershot camera and the CHDK firmware. The Easystar plane flies well and the foam can handle a hard landing. The neat thing about the plane is the model airplane is flown by radio control with the pilot wearing a FatShark head mounted video display. The video link is supplied by a tiny analog camera located on the nose of the airplane and a 900 MHz video transmitter. A Canon Powershot SD780IS camera is attached to the canopy of the Easystar plane and records photos or 720p HD video.

One of the most challenging parts of aerial photography is to lock in the right camera settings on the ground before the plane launches. I've put together an Excel spreadsheet that helps reduce some of the trial and error process in aerial photography. The spreadsheet calculates the required photo parameters to reduce motion blur, and capture photos with enough overlap for stitching into aerial mosaics. When I shoot aerial images with my Canon Powershot camera I use a CHDK script called the Countdown Intervalometer to trigger the photos.

Since most model airplane flights are 30 minutes or less, it can help to lock in the white balance and set the camera to use a CHDK based manual shutter speed override. This will keep the camera settings constant for the whole flight which makes it easier to stitch the images into an aerial mosaic using software like Microsoft ICE.

To make sure the camera will be in focus during a flight I set my Powershot camera to the mountain mode icon (infinity focus mode). If you still have blur in your aerial photos you need to figure out if you are seeing motion blur from a slow shutter speed, or a vibration based blur from the airframe or motor/propeller.

With a bit of detective work you can figure out what type of blur you have by reviewing your photos. If the blur is traveling in a single direction or a long arc you are witnessing motion blur that can be fixed by increasing the shutter speed & ISO settings on the camera.

If the blur looks wobbly you have a vibration based blur that can be solved by balancing your propeller and isolating your camera body from the model plane's airframe with a shock absorber like a piece of rubber or moongel pads.

Download

The aerial imaging spreadsheet is available as a free download in the Excel .xlsx format: Aerial_Imaging_Spreadsheet.xlsx

Spreadsheet Preview

Spreadsheet Calculations

Using the spreadsheet you can enter the following parameters:

  • flight altitude
  • ground level
  • camera lens mm
  • image sensor dimensions
  • image sensor resolution
  • shutter speed
  • flight speed
  • photo interval
  • image size
  • memory card size

The spreadsheet will then compute parameters like:

  • ground coverage area (object size) in mm and feet
  • the size of a pixel in feet, mm, and meters
  • distance traveled between photos in feet
  • photo overlap distance in feet and percentage
  • actual motion blur distance in pixels, percent, and feet based upon the shutter speed, image coverage area, and the air speed
  • estimated number of photos per flight based upon the memory card size, photo interval period, and flight duration
  • required flight distance and duration before the digital camera memory card is full

Note: The blue cells in the spreadsheet are editable, and the red cells should be left alone as they contain the formulas.

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An Aerial Tour of Privateers Island

By , March 28, 2012 1:04 pm
This is a photo of me holding a ready-to-launch EasyStar model airplane. The plane is fully loaded with camera gear and has a total weight of 1.3kg.

This is a photo of me holding a ready-to-launch EasyStar model airplane. The plane is fully loaded with camera gear and has a total weight of 1.3kg.

On March 21, 2012 my brother and I flew our model EasyStar airplane over Privateers Island in West Dover, Nova Scotia. The plane carried a Canon PowerShot SD780IS digital camera, a Garmin eTrex Legend GPS, and a wireless video camera.

We launched several flights that day starting around 11am in the morning. This is the first year that I can remember wearing a t-shirt and getting a sunburn in March!

During the vertical aerial photo flight we took several hundred photos. The main thing we noticed when we reviewed the aerial photos of Privateers Island was evidence of significant hurricane damage in the forest. There are large areas in the forest canopy that are now open clearings with a lot of fallen trees.

A vertical aerial photo of the launch site.

A vertical aerial photo of the launch site.

The hurricane damage is really visible on the southern part of Privateers Island.

The hurricane damage is really visible on the southern part of Privateers Island.

hurricane damage

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