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Creating Quality GCPs for Mapping: tips

In the example, the subject of interest is not a square so we distribute the points as best we can in the corners and center. You can also see some other measurement annotations in blue.

Hello,

An interesting note about placing quality Ground Control Points.

Any other useful tips?

From groundcontrolpoints.com:

To make a quality ground control points to use for georeferencing in drone mapping software, there are 4 key things to remember.

1) Use a Large, Clear Targets

Ideal GCP targets could be a large X marked on the ground, a checkerboard mat, or a circular target with a center point. You want to make sure your target has high contrast colors like black & white and that it is large enough to be easily visible from your flight altitude.

This is an example of a high quality GCP target spray painted onto the ground using a rectangular stencil.

circle-gcp-contour-lines.jpg?format=1000w

Another DIY approach we have seen is a 12" bucket lid stuck on a white plastic 14x14 access panel. Each of these are available at Home Depot, Lowe's, or your local hardware store.

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This gcp was made with a sheet of roofing rubber ($4.66 each) and vinyl stickers ($1 per 6" x 12" sheet) to create a simple checker pattern that is highly weather resistant.

  
  

2) Measure Your GCP Center with High Precision GPS

The GPS on your phone, tablet, or drone won't cut it!

You need an extremely precise GPS measurement to create a quality ground control point. To do this you will need a Real Time Kinematic (RTK) or Post Processing Kinematic (PPK) GPS receiver. Traditional examples include the Trimble R family of products (including the Trimble R8 pictured on the right) but recently low-cost alternatives like the Emlid Reach have entered the market.

RTK GPS is required for GCP in mapping contour lines

RTK GPS is required for GCP in mapping contour lines

3) Evenly Spread Your GCPs Through Your Map

Typically you will need a minimum of 4 GCPs but no more than 10 are usually required even for larger maps. A good strategy is use 5 GCPs located in the 4 corners of your map and the center. As you place your GCPs make sure you leave a minimum 50 ft buffer from your GCPs to the boundaries of your map.

In this example, the subjects of interest are the 2 star shaped buildings so we place our GCP as best we can around the corners and in center of our subjects.

In this example, the subjects of interest are the 2 star shaped buildings so we place our GCP as best we can around the corners and in center of our subjects.

4) Make Sure Your GCPs are Unobstructed and Clearly Visible

To create quality GCPs for drone mapping, your markers must be clearly visible from your flight altitude to be successfully processed. Visual obstructions like overhangs, snow, shade, or glare can make your GCPs difficult to identify in your map photos.



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Hey DIY-selfers!

NVIDIA Jetson TX1 is a system-on-module with impressive processing capabilities.
To get a glance of how powerful it is just take a look at the numbers in the description from NVIDIA:

“It's built around the revolutionary NVIDIA Maxwell™ architecture with 256 CUDA cores delivering over 1 TeraFLOPs of performance. 64-bit CPUs, 4K video encode and decode capabilities, and a camera interface capable of 1400 MPix/s make this the best system for embedded deep learning, computer vision, graphics, and GPU computing.”

Jetson TX1 makes a perfect companion computer for those who need to do heavy processing onboard such as video processing or image recognition. But to be used as a companion computer in a drone Jetson TX1 has to be connected to a carrier board. Unfortunately default carrier board for Jetson TX1 from the Developer Kit may be too big for a medium-sized drone. Thankfully there are other alternatives that are more suitable.
 
As many of diydrones members are already using it I hope this overview will be useful.

Let’s begin with the default carrier board as a starting point for comparison.
 
Nvidia Jetson TX1 Developer Kit
599$ with Jetson TX1 module ($299) and camera module included
https://www.nvidia.com/object/jetson-tx1-dev-kit.html

3689692674?profile=originalDefault carrier board has most of the necessary interfaces on standard ports and the kit also includes a camera module. It’s quite big and heavy to fit into the medium-sized drone, but if you are just starting playing around with Jetson TX1 then the default carrier is the best to begin with since most of the documentation and examples in the internet are using it.

Astro Carrier by Connect Tech Inc.
~$489.00
http://www.connecttech.com/sub/products/ASG001.asp

3689692749?profile=originalOne of the main features of this carrier is that it has 8 coax video inputs - this may be useful for projects that want to work with 360 degree vision. There’s no official price on the manufacturer’s website, but one of their dealers sells it for $489.

Elroy Carrier by Connect Tech Inc.
~$497.00
http://www.connecttech.com/sub/products/ASG002.asp
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This carrier is close to the previous one but seems like it’s more hacker-oriented. It has no coax video inputs, only two CSI inputs which is one more than Astro. It also provides access to additional GPIOs and SPI. As with the previous board there’s no official price on the manufacturer’s website, but one of their dealers sells it for $497.

Orbitty Carrier by Connect Tech Inc.
$175
http://www.connecttech.com/sub/products/ASG003.asp

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This is the cheapest carrier board available, but it still has most of the main interfaces like Ethernet, USB 3.0, HDMI etc. What it is lacking are the CSI video inputs, but for those using USB 3.0 cameras that should be no problem.

Auvidea J100
€199.00
http://www.auvidea.eu/index.php/2015-11-08-08-01-27/2016-02-03-12-30-02/j100-single-tx1-carrier-lite

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Great and affordable board. It’s main features are: four CSI video inputs and two USB 3.0 ports which allows to connect a lot of digital camera sensors. Most interfaces including USB are routed to custom connectors, so you’ll need special cables for that.

Auvidea J120
€219.00
http://www.auvidea.eu/index.php/2015-11-08-08-01-27/2016-02-03-12-30-02/j120-super-mini-computer-with-tx1

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J120 is my favorite here. It is little bit easier to use than its predecessor since it has standard Ethernet and USB ports. It also includes M2 slot for connection of SSDs and two CAN ports for connection of industrial equipment.

There’s also Auvidea J200 that is designed to carry two Jetson TX1 modules, but it is quite big so not included in the comparison.


Comparison chart

Here’s a simple comparison chart of the main features, hopefully it will be able to help to determine which board suits your needs better.

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If you know any other compact carrier boards or think that something should be included in the comparison chart feel free to post in the comments section, I will be happy to add the info.

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