Data Acquisition - Raw Images Quality Check

1. Description

The Data Acquisition module contains a raw image quality check to ensure the images uploaded correspond to the initial requirements.

2. List of criteria and corresponding rules

Category Associated quality check name Description Rules
Date of acquisition Date of acquisition
Check if the images are taken within the scheduled time window Outside scheduled time frame: Warning - "Data collected outside the specified time frame"

Inside scheduled time frame: Pass -  "Data collected within specified time frame"

Flight values

Image orientation
Check if image orientations are valid for mapping purposes

|pitch, roll| >= 25°: Error - "Orientation of some images are out of range"

|pitch, roll| >= 15°: Warning - "Orientation of some images is close to the limits"

|pitch, roll| < 15°: Pass - "All images have a valid orientation"

RTK Accuracy
Control RTK system accuracy
(only if RTKis available on the drone)

RTK (%) <= 75%: Error - "Low RTK accuracy within the survey"

75% < RTK (%) <= 90%: Warning - "Medium RTK accuracy within the survey"

RTK(%) > 90%: Pass - "High RTK accuracy within the survey"

If no RTK: "No RTK available

Note: "RTK (%)" = Pourcentage of image with fixed RTK position

RTK horizontal standard deviation
Evaluate RTK horizontal standard deviation (only if RTK is available on the drone)

Std deviation >=10cm: Error - "Bad RTK horizontal positions within the survey"

5cm < Std deviation  < 10cm: Warning - "Average RTK horizontal positions within the survey"

Std deviation <=5 cm: Pass - "Good RTK horizontal positions within the survey"

If no RTK horizontal positions: "RTK horizontal positions not available"

Note: Std deviation: √(RtkStdLon² + RtkStdLat²)

GSD ratio
Evaluate if the GSD ratio and thus the risk of blur is acceptable within the survey

GSD ratio >= 1.5: Error - "High risk of longitudinal blur on the images"

0.8 < GSD ratio < 1.5: Warning - "Potential risk of longitudinal blur on the images"

GSD ratio <= 0.8: Pass - "Low risk of longitudinal blur on the images"

If GSD ratio can't be calculated: "GSD ratio not available"

Note: GSD ratio = (flightSpeed_m_s * shutterSpeed_s) / gsd_m_px


  • flightSpeed_m_s = √(FlightXSpeed² + FlightYSpeed²)
  • gsd_m_px = (pixelSize_mm * relativeAltitude_m) / focalLength_mm
Sensor values
Check the percentage of images with ISO value > 400

(% images ISO>400) > 20%: Error - "More than 20% of the images have an ISO value higher than 400"

0< (% images ISO>400) < 20% : Warning - "Between 1% and 20% of the images have an ISO value higher than 400"

(% images ISO>400) = 0: Pass - "ISO value is lower than 400 for all images"

Check the aperture within the survey

Aperture < 4.5: Error - "Aperture < 4.5"

4.5 ⩽ Aperture < 5.6: Warning - "4.5 ⩽ Aperture < 5.6"

Aperture 5.6: Pass - "Aperture ⩾ 5,6"

Additional checks Sunlight conditions
Check if the local time of acquisition is outside of the hotspot time window
outside of low luminosity conditions, based on the sun's position at the time and position at the beginning and end of the flight

"Dark" period is when the sun is below 30° elevation. If the flight intersects a dark period: Error - "Sunlight is not high enough during this acquisition"

Hotspot is when the sun is higher than 90°-FOV/2. If the flight intersects a hotspot: Warning - "Sun light may be too high during this acquisition"

If no dark period or hotspot: Pass - "Sun light conditions seem acceptable for this acquisition"

Note: If sensor width, pixel size and lens focal length are not available then FOV cannot be computed and hotspot elevation threshold is set arbitrarily to 65°.

FOV: Field of View

Missing images (for mapping purposes) Detect the flight axis and detect holes in the axis by analyzing the spacing distribution between images on the axis If missing images: Error - "X holes detected in image collection axes"
If there are no missing images: Pass

"Image collection axes seem to be complete"

Missing bands (Multispectral sensor)  For all images locations, the expected number of bands is checked If missing bands: Error - "Some missing bands (X) have been detected"
If no missing bands: Pass - "No missing bands detected"
Calibration targets Calibration targets (Multispectral sensor) Check if the Calibration target is available If calibration target missing: Error - "No calibration targets have been detected for some sensor bands (Sensor band name 1, Sensor band name 2...)"
If calibration target available: Pass - "X calibration targets detected"