Ive made some from tiles and a set from masonite. Most of the time I just?ÿpaint them on the ground. Our favorite color scheme is flo blue and white checkerboard with a mag hub in the center. Its very easy to spot without zooming in tight. We also paint the point number about 6 or 8 inches tall next to the panel.?ÿ
Type of target depends on the job.
Painted crosses are OK - on hard surfaces a 9 inch white cross, arms 2 inches wide can be seen from 400 ft. I normally put a nail in the centre, so it can be used at a later date or as a detail station for ground survey. 1 inch arms would do from 200 ft.
For temporary boards - recycled cardboard boxes are a good source. Cut to squares and mark crosses with tape (white or black).
For permanent boards - Correx plastic sheet cut to squares and fixed to a centre peg with a screw and large mud washer (also acts as a centring point for the GPS rod and saves surveyor sticking rod through board!).
Boards last longer if you stick two layers together, with corrugations running at right angles - hot glue gun is fine. Running 2 in. tape right round to make the cross also strengthens the board.
Board sheet tends to come in multiples of 4 ft., so size cut tends also to be a division of that, but smaller offcuts, 6 in up, make good temporary targets on bare soil. Size of target also depends on how long it is intended to stay. If you are flying a regular site over several years a 2 ft. target might be better - with a black plastic sheet surround to keep the vegetation at bay. You have to weigh up the time spent on making something long lived, against the time to go out and reset targets.
Remember, perfect shape isn't critical. The only critical bit is the 2 square inches in the middle that marks the measured position - the rest just helps you to find the spot. Try and get the board to sit level; that will improve the height reading you get from the target.
Road markings are fine, if they are clear. Worn markings may show up differently on camera to how the surveyor sees them on the ground. If in doubt "tidy" them up with a bit of paint before you fly.
JT,
We find that 180 to 250ft AGL is ideal with 20MP camera. This should be acceptable for your Landfill project, as we discussed. Lower AGL is better for high detail but requires exponentially?ÿmore photos, more processing time, and larger?ÿortho images?ÿ/ point clouds. It depends on your application and deliverable to the client. Your?ÿ PDF ortho is very pixelated, which is expected in order to post it here. Our typical high-resolution?ÿorthoimage is 700Mb in TIF (Pix4D). You may want to try processing with one of the free 30 day trial?ÿonline cloud processing companies.?ÿ
Here is a screen from at 200ft AGL at shown at 38%, 100% zoom (703Mb), and a?ÿscreenshot of the deliverable (13Mb PDF).
Notice the target in the bottom right corner.
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"Small unmanned aircraft may not operate over any persons
not directly participating in the operation, not under a
covered structure, and not inside a covered stationary
vehicle."
25 foot separation from moving vehicles? I couldn't find the direct citation but remember it from study material.
One of the recent notices from the FAA dealt with this. The message stated flying over roadways was not strictly prohibited and suggested flying at right angles to roads in use to minimize exposure.
One of the recent notices from the FAA dealt with this. The message stated flying over roadways was not strictly prohibited and suggested flying at right angles to roads in use to minimize exposure.
Depending upon the wind direction. An alternative would be to fly several legs parallel to the road but offset each side. The higher you fly the more offset you can have and still get overlap. Also depends on the road use - should be no problem if the traffic is very light as there may be no vehicle on the road whilst you are flying. I'd rather do that than have the additional risk of crossing the road 20 or 30 times.
When we have roads bounding the site we've made a habit of flying a full loop offset around the outside of the roads (housing permitting) just to ensure we have a good fill in on the edges of the main grid.
