UAV Accuracy, Repeatability: Is it Real?

I get to talk to a lot of UAV folks. Typically they are new practitioners who are looking for a fast and inexpensive method of doing Ground Control (GC) and Ground Check Points (GCP) for jobs that are going to be flown using fixed or rotary wing aircraft. We get involved because of the affordability of the iG3s static solution and our great RTK offerings.

One of the scary things that I am figuring out is that the people who are flying these jobs don’t have much of a survey background.

I am just going to throw this thought out: If you are selling UAV services in the USA and don’t have a good handle on these four items:

  • US Survey Feet vs. International Feet
  • IGS08 vs. NAD83 2011 2010.0 (What is a realization, what is an epoch? If you don’t know then you don’t know.)
  • Orthometric vs. Ellipsoid (+ GPS Derived Heights, i.e. GEOID Separation)
  • Accuracy vs. Repeatability

Then I think that you are precluded from making any accuracy claims!

In other words, if you don’t explicitly know the difference between IGS08 and NAD83; then you CAN NOT possibly claim on your website that you are delivering sub-centimeter results. I mean, you just can’t.

I happened on a great white paper last Friday [ Strix ] [ PDF Link ] that does a great job of actually empirically looking at 225 flights over the same test bed. It delves into the differences in lighting, flight patterns, control spacing and more.

Basically I think that this stuff might actually be rocket science. At least lets be clear that it is not simple.

🙂 M

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SurvCE: Send NMEA out the Data Collector Serial Port

SurvCE allows you to send NMEA sentences out the data collector serial port.

Here are some tricks and hints on getting it work:

[ Setup SurvCE to Send NMEA Messages out Data Collector COM Port ]

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PPP via Serial Port on Win 10 Creator’s Edition

Wow. Creator’s Edition is just one thing after another that used to work and no longer works.

We use PPP over serial cables to communicate with GNSS engines here all the time. The latest round of updates has disabled PPP on every single machine that used to work.

Below are instructions for making it work under Windows 10. I have no idea how to make it work under Windows 7 now (and that used to be the easy OS.)

Anyway, Keep Reading: [ PPPWindows10SetupNotes_RevA ]….

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Setting up a Nautix X8 Wi-Fi

Setting up Wi-Fi on the X8 is not difficult. But it is different than most other data collectors.

Continue reading for my notes with pictures [ NautixX8_WiFi_Setup … ]


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NGS OPUS Won’t Process my GPS Observation File!


I collected static data with my (xyz) GPS receiver, just like I always do. It was in a wide open area, but when I submit data it reports that it cannot process the file or the vectors because they are noisy or fewer than 3 useable stations remain.


There are a lot of possible answers, but in this case the error message may be correct: “There are no nearby CORS stations WITH data.”

Let’s look at an example. [ Continue Reading …  OPUSWontProcess_R001 ]

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Checking the OS Version on a Surveyor 2

How do you check for the current OS Version on a Carlson Surveyor 2 (or Mini-2)?

[ OSVersionOnSurveyor2_R001 ]


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Example Metadata for GPS Job

Wow, there has been a lot of ink spilt on North Arrows and projection declarations for jobs based on GPS data.

Since I am not a licensed surveyor, my opinion does not count. But I get asked all the time. So here is an example of what I might do as a minimum:

I, Joe Blow, do hereby certify that I am a Professional Land Surveyor, holding 
certificate 99999 as prescribed by the State of Chaos.
I further certify that I have prepared the diagram represented herein and that
the same is an accurate representation of a survey, and was conducted under
my direct supervision.

  The Benchmark for this project is CP201

Coordinate System and Projection Information
  Horizontal Datum = NAD83, North American Datum 1983,
                     2011 Realization 2010.0 Epoch
  GPS Control = Maine DOT Virtual Reference System (VRS)
  Vertical Datum = NAVD88, North American Vertical Datum of 1988, 
                   GPS Derived
  GEOID (used for GPS Derived Heights) = GEOID12B (NGS)
  Ellipsoid = GRS1980
  Projection = Maine West NAD83 State Plane Coordinates 
  Distance = US Survey Feet (1 Meter = 3937/1200 US Survey Feet)

  Distances are Grid distances converted to Ground using a Combined Scale Factor
  The Combined Scale Factor (0.99996067) for this project was derived at
    Control Point 201
          CP201 = 44 2 55.34000 N 69 58 23.05000 W NAD83
          Ellipsoid Height 215.562 ft
          GEOID            -57.100 ft
          Ortho Height     272.662 ft [NAVD88 (Computed using GEOID12B)]

    Example: 9,857.824 SFeet Grid = 9,858.206 SFeet Ground

    Bearings are with respect to State Plane Grid North
    Declination at
       TN-SP  0°  8’  4.57”
       TN-MN 15° 36’ 37” (2017 Estimate)


{My Seal}
Joe Blow
Chaos PLS Number 99999

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