UAV Flight Operations and Data Accuracy€¦ · UAV Flight Operations and. Data Accuracy....

UAV Flight Operations andData Accuracy

Precision. Accuracy. Reliability

Part One: MappingWhy is Mapping different?Flight Operations and PlanningIntegration of Ground Control

Part Two: AccuracyNSSDA and ASPRS standards Translation to NMA Accuracy Assessments

AGENDA

Part 1MAPPING WITH DRONES


OVERVIEW

Get Legal:Section 333 or Section 107, Insurance

OVERVIEW


Get Equipment: Rotocopter or Fixed wing?RTK? Camera? LiDAR?

OVERVIEW



Get Proficient:Takeoff and Land and…Crash

OVERVIEW



Get Proficient:Takeoff and Land and…Crash

Get Tools:Plan, Control, ProcessAutonomous flight

Sensors and Platforms

“ITS THE DATA, STUPID”

• Most vendors focus on the promise of automation.


THERE IS NO EASY BUTTON

https://www.altavian.com/2017/01/09/one-button-survey-fallacy/

https://www.altavian.com/2017/01/09/one-button-survey-fallacy/

PURPOSE

PURPOSE

Imagery

Video

Orthos

Point Cloud*

DSM

DEM

Planimetrics

Analytics

3D Objects

Point Cloud*

Obliques

What is this?

ERROR

• Horizontal and Vertical Error translate to

VOLUMETRIC ERROR- even when within specs

• Change detection can only be done within the

accuracy limits of the sensor.

• Fly the same site twice in the same day with

the same control. Check the difference.

DATA QUALITY TRIANGLE

DATA QUALITY

Ensure data quality by adapting existing

standards and best practices

PRECISION

QUALITY

ACCURACY

ACCURACY

REPEATABLITY

Copyright © 2016 Spatial Analytix, LLC

http://www.spatialanalytixllc.com/

Flight Planning & Operations

FLIGHT PLANNING

Flight Lines to the edge of the AOI

Flight Lines beyond the AOI

FLIGHT PLANNING

FLIGHT PLANNING

Control Points

FLIGHT PLANNING

Check Points

FLIGHT PLANNING

GCP Planning

• No matter how you fly, GCPs control the accuracy

• 5-10 points per site

• Re-use existing known control when possible

• The GCP layout and the flight plan done together.

• Put GCPs in overlap areas and isolated areas

• GCP persistence-Adapt your plan over time

• Augment in areas of low confidence or obscured

GCP Planning

• Use an appropriate target

• Include KMZ/ASCII/Shape

• Need to be visible, recoverable, numbered.

• Be Practical!

Photo. Scale Thickness of Leg (T) Length of Legs (L)

1:1800 6 Inches(150mm) 3 Feet(0.9m)

1:2400 6 Inches(150mm) 3 Feet(0.9m)

1:3000 6 Inches(150mm) 4 Feet(1.2m)

1:3600 6 Inches(150mm) 4 Feet(1.2m)

1:4200 6 Inches(150mm) 5 Feet(1.5m)

http://geobits.io/

https://www.propelleraero.com/aeropoints

Data Processing

ProcessProcess

Collect

Deliver

UAV MAPPING OVERVIEW

Imagery

Video

Orthos

Point Cloud*

DSM

DEM

Planimetrics

Analytics

3D Objects

Point Cloud*

Obliques

Level 0 Level 1 Level 2 Level 3 Level 4




Raw ImagesGPS LogCamera Orientation




Automated ProcessingQC ChecksFlight Validation





Ground ControlOrtho- controlRTK -in air






Mapping Products






Mapping Products

Analysis Products

Level Description What Do you Get? Data Quality TriangleLevel 0 Flight Operations

Raw DataGPS Log FileFlight Line LogOutline of AreaGeotag Imagery

Repeatability

Level 1 Automated Processing(cloud based services)

Image mosaicPoint cloudInitial Surface Model (DSM)3D Mesh

Precision

Level 2 Ground Controlled Survey GradeIntegrated control with known accuracy

Accuracy

Level 3 Topographic Data Point Cloud ClassificationBare Earth Elevation modelsSurface Constraints/BreaklinesDSM/DEM

Stitching multiple Flights Manual Tie PointsQuality Control

Level 4 Analytics/Derivatives ContoursPlanimetricsVolumesChange detectionHabitat mapping DrainageLand Cover/Vegetation/ImperviousFeature Extraction

WHAT YOU DON’T WANT TO SEE

PART 3- The Results

• Screen Shots of Tepper Quad Case Study

WHAT YOU DO WANT TO SEE

Part 2ACCURACY


NMAS and the NSSDANMAS- 1947

Paper Map produced at a certain scale Not appropriate to use for digital data “2 foot accuracy” and “1 foot accuracy” terms no

longer apply, but are still WIDELY used

Standards

NSSDA and NMASNMAS- 1947

Paper Map produced at a certain scale Not appropriate to use for digital data “2 foot accuracy” and “1 foot accuracy” terms

are still WIDELY used

NSSDA – 1998 Applies to raster, point or vector data Must compare your data against a “reference” Reference must be 3x more accurate RMSE vs 95% Accuracy

Standards

RMSE vs 95% Accuracy in NSSDARMSE is a measure of the data itself- the ERROR measured

in the datai.e., RMSEz = 0.312 ft

95% confidence is a measure of selected data points against a target, or “tested to meet” standardi.e., 95% of the measurements will be within a certain threshold

of a “reference” or “true” valueNote: 5% of the measurements may not meet the target

threshold

Accuracy(x) = 1.7308 * RMSE(z)

Accuracy(z) = 1.9600 * RMSE(z)

Standards

“Produced to meet…”

Vs

“Tested to meet…”

2010- FEMA Policy MemorandumAligns FEMA Appendix A with USGS Lidar Guidelines and

Base Specifications v 13

Defines terms DEM, DSM, DTM

Calls out NSSDA as the standard for Accuracy Reporting, supplemented by NDEP 2004 and ASPRS 2004 for vertical accuracy.

“All of these standards, designed for digital elevation data, replace the National Map Accuracy Standard (NMAS)”

Standards

Horizontal Standards


UAV

Converting from NMAS to ASPRS 2014 Standards:

Given a map or orthoimagery with a horizontal accuracy of RMSEx = RMSEy = 15 cmaccording to the new 2014 standard, what is the equivalent accuracy andmap scale according to the legacy National Map Accuracy Standard (NMAS)?

Exercise Problems


Given a map or orthoimagery with a horizontal accuracy of RMSEx = RMSEy = 15 cmaccording to the new 2014 standard, what is the equivalent accuracy andmap scale according to the legacy National Map Accuracy Standard (NMAS)?

1:380 or 1”=32’

Exercise Problems


Given mapping requirements for creating planimetric data at1:400 scale:

A) What is the lowest resolution imagery that can be used?

B) What is the horizontal accuracy requirement for the orthoimagery?

Exercise Problems




15cm or 6”B) What is the horizontal accuracy requirement for the orthoimagery?

-same-

Exercise Problems




15cm or 6”B) What is the horizontal accuracy requirement for the orthoimagery?

-same-What if you get 6” imagery but the accuracy reported is +/-1ft?

Exercise Problems

Surface ModelingVertical Standards

Surface Modeling FEMA- NPS should be equal to or less than the DEM post spacing

(resolution) required

1-meter DEM for 1ft contours 2-meter DEM for 2ft contours 5-meter DEM for 5ft contours

0.7m NPS -> 2ppsm -> 1m DEM -> 1ft contours (QL 2) 1.4m NPS -> 0.5ppsm -> 2m DEM -> 2 ft contours (QL 3)

Note: Higher density data may still fail vertical RMSE testLower density data may meet higher accuracy tests for

discrete points.Accuracy is tested from a sample of points against the surface model,

regardless of the point density

Vertical Standards

Vertical Standards


Given an elevation dataset with a vertical accuracy of RMSEz = 10 cmaccording to the new 2014 standard, what is the National Map Accuracy Standard (NMAS)? equivalent contour interval?

Vertical Standards


Given an elevation dataset with a vertical accuracy of RMSEz = 10 cmaccording to the new 2014 standard, what is the equivalent contour intervalaccording to the legacy National Map Accuracy Standard (NMAS)?

32.9cm or 1ft


Given the requirement for 6” contour elevation data, what is the minimum point spacing and/or point density?

Vertical Standards


Given the requirement for 6” contour elevation data, what is the minimum point spacing and/or point density?

NPS = 35cm or ~1ftNPD = 8 ppsm

Measuring Accuracy

I have drone data that is 1” pixel resolution ortho and 6” contours.

How accurate is it?

Measuring Accuracy

I have drone data that is 1” pixel resolution ortho and 6” contours.

How accurate is it?

Who knows?....

Measuring Accuracy

“Produced to meet…”

Vs

“Tested to meet…”

“In no case shall orthoimagery or planimetric accuracy be based on less than 20 checkpoints.”

Vertical checkpoints on slopes <10% Checkpoints at intervals of at least 10% of the diagonal At least 20% of the points are located in each quadrant

>20%

Measuring Accuracy

NSSDA: minimum of 20 points NSSDA: 95% Accuracy means 1 point can fail FEMA and ASPRS: 20 per land cover type USGS: use land cover types >10% of area LiDAR Projects: Typically 100 points

Reference must be 3X target accuracy

For UAS collections- MINIMUM of 20 POINTS !!!

Meeting accuracy specs does not necessarily equate to having quality data

Measuring Accuracy

If I use ground control with +/- 0.1ft accuracy for each point on a UAV survey, And use the same to collect checkpoints across the project area, how do I report the resulting accuracy of the planimetrics and topo?

Measuring Accuracy

If I use ground control with +/- 0.1ft accuracy for each point on a UAV survey, And use the same to collect checkpoints across the project area, how do I report the resulting accuracy of the planimetrics and topo?

If UAV imagery is ~1inch 2.5cm Accuracy Class

0.1ft 3cm

3cm Checkpoints = 3x target accuracy = 9cm Accuracy Class

10cm Accuracy Class = 1:400 Planimetrics, 1ft contours

TESTED TO MEET Accuracy is only as good as the checkpoints used to TEST.

If you want to prove 0.1ft Accuracy (3cm)then you need 1cm Accurate Checkpoints

Measuring Accuracy


THERE IS NO EASY BUTTON

UAV Flight Operations and Data Accuracy€¦ · UAV Flight Operations and. Data Accuracy....

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Transcript of UAV Flight Operations and Data Accuracy€¦ · UAV Flight Operations and. Data Accuracy....