Earth Observation for Citizen Science Validation, or Citizen Science for Earth Observation Validation? The Role of Quality Assurance of Volunteered Observations
Abstract
:1. Introduction
QA Case Study Background
2. Quality Assurance and Quality Control Framework
3. Designing the Japanese Knotweed Quality Assurance
4. Using Citizen Science for Earth Observation Validation
4.1. Without Quality Assurance of the Citizen Science Data
- CS data with no score (25/177) and score <0.2 (20/177) represent an omission for high-risk zones of 45/177 (25%) and correcting for ground truth gives 39/161 (24%).
- CS data with score >0.5 represent accurate areas, 120/177 (68%), but 10/120 (8%) points wrongly identified JKW so a corrected accuracy of 110/177 (62%) with a commission of 8%.
4.2. With Quality Assurance of the Citizen Science Data
- CS data with no score (10/66) or score <0.2 (9/66) represent omission areas of 19/66 (29%).
- CS data with score >0.5 represent accurate areas, 41/66 (62%).
4.3. With Line of Sight Correction in the QA for the Citizen Science Data
- CS data with no score represents omission areas, 0/72 (0%).
- CS data with score >0.5 represent accurate areas, 72/72 (100%), correcting for ground truth gives 67/72 (93%).
- CS data with score <0.2 (which was the low risk value in the EO data) represents an omission rate of 0/72 (0%).
5. Using Earth Observation to Improve Citizen Science Data Quality
5.1. CS Data Validation
5.2. Iterative Paradigm
6. Discussion
7. Conclusions
Acknowledgments
Author Contributions
Conflicts of Interest
Abbreviations
CIR | Colored Infra-Red |
COBWEB | Citizen OBservatory WEB |
CS | Citizen Science |
DEM | Digital Elevation Model |
EO | Earth Observation |
FP7 | Framework Program 7 |
IAS | Invasive Alien Species |
JKW | Japanese KnotWeed |
INNS | Invasive Non-Native Species |
LiDAR | Light Detection And Ranging |
LoS | Line of Sight |
QA | Quality Assurance |
QAwAT | Quality Assurance workflow Authoring Tool |
QC | Quality Controls |
SNP | Snowdonia National Park |
VGI | Volunteered Geographic Information |
Appendix A
Pseudo Code | Short Description | Quality elements metadata created or updated: DQ ISO19157 producer model GVQ GeoViQUA’s feedback model (simplified) CSQ COBWEB’s stakeholder model |
---|---|---|
pillar1.LocationBasedServicePosition.RelativePositionLineOfSight | ||
#start input("citizen position, DEM, tilt and bearing of the phone ") LoSpt=computeTheLoSpoint(position, DEM, tilt, bearing) input("input DEM uncertainty and position uncertainty") d=distance(position,LoSpoint) sd= uncertaintyofDistance(d,DEM_Accuracy, DQ_AbsoluteExternalPositionalAccuracy) input("choosing Threshold distance", "OptionSwap=TRUE or FALSE", p-below=0.6) DQ_topologicalConsistency=probability(GaussianDistribution(d,sd^2)<=Threshold) if(OptionSwap & DQ_topologicalConsistency < p-below) swapToLoS(position,LoSpoint) update(DQ_TopologicalConsistency, DQ_Usablility) update(DQ_AbsoluteExternalPositionalAccuracy) #end | ||
Compute the line of sight, aiming point and distance to it. Swap to LoS point under certain conditions DEM ThresholdDistance p-below OptionSwap | DQ_UsabilityElement DQ_TopologicalConsistency -LoS.point / DQ_AbsoluteExternalPositionalAccuracy with scope defined as “LoS” . | |
pillar2.Cleaning.LocationQuality | ||
#start input("input citizen position, DQlevelThreshold, PosUnThreshold, methods") for each observation { for each method in methods { DQ_usability=evaluateRule(DQ_AbsoluteExternalPositionalAccuracy, DQ_usability, DQ_topologicalconsistency, DQ_conceptualconsistency) } } update(CSQs) #end | ||
According to the study requirement check if position is correct and/or can be corrected methods: “pillar1.WithinPoly”, ”pillar1.LineOFSight”, “pillar1,ContainsPoly”, “pillar1.GetSpatialAccuracy”,” pillar4.or pillar1.DistanceTo” DQlevelThreshold PosUncertaintyThreshold | DQ_UsabilityElement CSQ_Vagueness CSQ_Judgement CSQ_Reliability CSQ_Validity | |
pillar3.AutomaticValidation.PhotoQuality | ||
#start input("input citizen captured photo, blurThreshold," ) edgeImage=LaplaceTrasnform(photo) usable=evaluateRule(edgeImage, blurThreshold) update(DQ_usability, DQ_DomainConsistency, CSQ_judgement, CSQ_trust) message(usable) #end | ||
Test on sharpness of the image using the method of edge detection from Laplace transform. BlurThreshold | DQ_UsabilityElement DQ_DomainConsistency CSQ_Reliability CSQ_Trust -dynamic: <message> “Can you take another picture?” | |
pillar5.Model-basedValidation.ProximitySuitabilityScore | ||
#start input("input citizen position, buffersize, attribute") ProximPol=findNearby(buffersize) score=summaryMeasure(calculweightDistance(ProximPol),values(ProximPol, attribute)) updateRules(DQs,CSQs,GVQs, score) #end | ||
Deriving the likelihood of the observed occurrence (citizen captured data) from polygon proximity to a model-estimate one (e.g. suitability likelihood) modelled data attribute buffersize | DQ_UsabilityElement DQ_ThematicClassificationCorrectness DQ_AbsoluteExternalPositionalAccuracy DQ_RelativeInternalPositionalAccuracy GVQ_PositiveFeedback GVQ_NegativeFeedback CSQ_Judgement CSQ_Reliability CSQ_Validity CSQ_Trust | |
pillar4.AuthoritativeDataComparison.ProximitySuitabilityScore | ||
#start input("input citizen position, buffersize, attribute") ProximPol=findNearby(buffersize) score=summaryMeasure(calculweightDistance(ProximPol) updateRules(DQs,CSQs,GVQs, score) #end | ||
Deriving the likelihood of the observed occurrence (citizen captured data) from polygon proximity to a given authoritative data (e.g. existing observed occurrences) Authoritative data Buffersize Note: comparing to pillar5 attribute value is 1 as authoritative data. | DQ_UsabilityElement DQ_DomainConsistency DQ_ThematicClassificationCorrectness DQ_NonQuantitativeAttributeCorrectness DQ_AbsoluteExternalPositionalAccuracy DQ_RelativeInternalPositionalAccuracy GVQ_PositiveFeedback GVQ_NegativeFeedback CSQ_Judgement CSQ_Reliability CSQ_Validity CSQ_Trust | |
pillar4.AuthoritativeDataComparison.PointInPolygon | ||
#start input("citizen observation, thematicAgreement, AuthData, Buffersize") InPol=evaluateIn(observation.DQ_AbsolutePositionInternalPositionalAccuracy, AuthData.DQ_AbsolutePositionInternalPositionalAccuracy, AuthData, Buffersize) IniScore=EvaluateOverlapAreas(InPol, observation, uncertainties) updateRules(DQs,CSQs,GVQs, IniScore) if(not InPol) { ProxPol=evaluateNear(Obs.DQ_AbsolutePositionInternalPositionalAccuracy, Auth.DQ_AbsolutePositionInternalPositionalAccuracy) ProxScore=Evaluate(ProxPol, Obs, uncertainties) updateRules(DQs,CSQs,GVQs, ProxScore) } #end | ||
given the position and its uncertainty checking if a point belongs to a polygon then concluding on relative position accuracy and 'relative' semantic therefore usability and attribute accuracies Authoritative data ThematicAgreement | DQ_UsabilityElement DQ_ThematicClassificationCorrectness DQ_NonQuantitativeAttributeCorrectness DQ_QuantitativeAttributeAccuracy DQ_AbsoluteExternalPositionalAccuracy DQ_GriddedDataPositionalAccuracy DQ_RelativeInternalPositionalAccuracy GVQ_PositiveFeedback GVQ_NegativeFeedback CSQ_Judgement CSQ_Reliability CSQ_Validity CSQ_Trust |
Appendix B
DQ | Quality Element DQ_ | Definition Extracted from the ISO19157 |
---|---|---|
01 | UsabilityElement | Degree of adherence to as specific set of data quality requirements. |
02 | CompletenessCommission | Excess data present in a dataset. |
03 | CompletenessOmission | Absence of data in a dataset. |
04 | ThematicClassificationCorrectness | Comparison of the classes assigned to features or their attributes to a universe of discourse (e.g., ground truth or reference data). |
05 | NonQuantitativeAttributeCorrectness | Whether a non-quantitative attribute is correct or incorrect. |
06 | QuantitativeAttributeAccuracy | Closeness of the value of a quantitative attribute to a value accepted as or known to be true. |
07 | ConceptualConsistency | Adherence to rules of the conceptual schema. |
08 | DomainConsistency | Adherence of values to the value domains. |
09 | FormatConsistency | Degree to which data is stored in accordance with the physical structure of the dataset. |
10 | TopologicalConsistency | Correctness of the explicitly encoded topological characteristics of a database. |
11 | AccuracyOfATimeMeasurement | Closeness of reported time measurements to values accepted as or known to be true. |
12 | TemporalConsistency | Correctness of the order of events. |
13 | TemporalValidity | Validity of data with respect to time. |
14 | AbsoluteExternalPositionalAccuracy | Closeness of reported coordinate values to values accepted as or being true. |
15 | GriddedDataPositionalAccuracy | Closeness of gridded data spatial position values to values accepted as or being true. |
16 | RelativeInternalPositionalAccuracy | Closeness of the relative positions of features in a dataset to their respective relative positions accepted as or being true. |
GVQ_ | Quality Element GVQ_ | Definition |
---|---|---|
01 | PositiveFeedback | Number of positive feedbacks to the used data |
02 | NegativeFeedback | Number of negative feedbacks to the used data |
CSQ_ | Quality Element CSQ_ | Definition |
---|---|---|
01 | Vagueness | Inability to make a clear-cut choice (i.e., lack of classifying capability). |
02 | Ambiguity | Incompatibility of the choices or descriptions made (i.e., lack of understanding, of clarity). |
03 | Judgment | Accuracy of choice or decision in a relation to something known to be true (i.e., perception capability and interpretation). |
04 | Reliability | Consistency in choices / decisions (i.e., testing against itself). |
05 | Validity | Coherence with other people’s choices (i.e., against other knowledge). |
06 | Trust | Confidence accumulated over other criterion concerning data captured previously (linked to reliability, validity and reputability). |
07 | NbControls | Total number of controls over all contributions of this volunteer. |
Appendix C
Declared Distance | N (Total 177) | LoS Distance (38/177) |
---|---|---|
Close (<1 m) | 73 | N = 10 out of * 73, Min. 1st Qu. Median Mean 3rd Qu. Max. 1.5 3.1 6.5 12.7 15.0 59.3 |
Nearby (1 m–3 m) | 30 | N = 9 out of * 30, Min. 1st Qu. Median Mean 3rd Qu. Max. 3.5 5.8 14.8 213.5 516.9 687.8 |
Far (3 m–10 m) | 39 | N = 13 out of * 39, Min. 1st Qu. Median Mean 3rd Qu. Max. 1.5 2.0 16.5 125.0 175.7 642.3 |
Very far (>10 m) | 34 | N = 6 out of * 34, Min. 1st Qu. Median Mean 3rd Qu. Max. 1.5 2.4 5.0 11.3 6.9 47.1 |
missing | 1 | - |
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Pillar Name | Pillar Description |
---|---|
Pillar 1: Positioning | Location, position and accuracy: focusing on the position of the user and of the targeted feature (if any), local condition or constraints (e.g., authoritative polygon, navigation, routing, etc.). |
Pillar 2: Cleaning | Erroneous entries, mistakes, malicious entries: Erroneous, true mistakes, intentional mistakes, removals, corrections are checked for the position and for the attributes. Feedback mechanism can be an important part of this pillar if the mistakes can be corrected. |
Pillar 3: Automatic Validation | Simple checks, topology relations and attribute ranges: Carries further the cleaning aspects by validating potential good contributions. Its aim is towards positive rewarding with more inclusive rules than with Pillar 2 focusing more on excluding rules. |
Pillar 4: Authoritative Data Comparison | Comparison of submitted observations with authoritative data: Either on attributes or position performs statistical test, (fuzzy) logic rule based test qualifying the data captured or reversely qualifies the authoritative data. Knowledge of the metadata of the authoritative data is paramount. |
Pillar 5: Model-Based Validation | Utilizing statistical and behavioral models: Extends Pillar 4 testing against modeled data (e.g., physical models, behavioral models) and other user contributed data within the same context. This may use intensively fuzzy logics and interactions with the user within a feedback mechanism of interactive surveying. (If some tests will be similar to Pillar 4 the outcome in quality elements can be different). |
Pillar 6: Linked Data Analysis | Data mining techniques and utilizing social media outputs: Extends Pillar 5 testing to using various social media data or related data sources within a linked data framework. Tests are driven by a more correlative paradigm than in previous pillars. |
Pillar 7: Semantic Harmonization | Conformance enrichment and harmonization in relation to existing ontologies: Level of discrepancy of the data captured to existing ontology or crowd agreement is transformed into data quality information. In the meantime, data transformation to meet harmonization can take place. |
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Share and Cite
Leibovici, D.G.; Williams, J.; Rosser, J.F.; Hodges, C.; Chapman, C.; Higgins, C.; Jackson, M.J. Earth Observation for Citizen Science Validation, or Citizen Science for Earth Observation Validation? The Role of Quality Assurance of Volunteered Observations. Data 2017, 2, 35. https://doi.org/10.3390/data2040035
Leibovici DG, Williams J, Rosser JF, Hodges C, Chapman C, Higgins C, Jackson MJ. Earth Observation for Citizen Science Validation, or Citizen Science for Earth Observation Validation? The Role of Quality Assurance of Volunteered Observations. Data. 2017; 2(4):35. https://doi.org/10.3390/data2040035
Chicago/Turabian StyleLeibovici, Didier G., Jamie Williams, Julian F. Rosser, Crona Hodges, Colin Chapman, Chris Higgins, and Mike J. Jackson. 2017. "Earth Observation for Citizen Science Validation, or Citizen Science for Earth Observation Validation? The Role of Quality Assurance of Volunteered Observations" Data 2, no. 4: 35. https://doi.org/10.3390/data2040035