Science underpinning archaeological detection: DART
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A presentation by Anthony Beck presented at the workshop "Potential of satellite images and hyper/multi-spectral recording in archaeology" Poznan – 31st June 2012
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Science underpinning archaeological detection: DART
- 1. DART – Archaeological detection Anthony (Ant) Beck Twitter: AntArch Potential of satellite images and hyper/multi-spectral recording in archaeology Poznan – 31st June 2012 School of Computing Faculty of Engineering
- 2. Overview •How do we detect stuff •Why DART •Going back to first principles •DART overview •Platforms •Knowledge base – impact on deployment
- 3. Archaeological Prospection What is the basis for detection We detect Contrast: • Between the expression of the remains and the local 'background' value Direct Contrast: • where a measurement, which exhibits a detectable contrast with its surroundings, is taken directly from an archaeological residue. Proxy Contrast: • where a measurement, which exhibits a detectable contrast with its surroundings, is taken indirectly from an archaeological residue (for example from a crop mark).
- 4. Archaeological Prospection These attributes may be masked or accentuated by a variety of other phenomena http://www.youtube.com/v/UfOi_7Os7kA
- 5. Archaeological Prospection What is the basis for detection Micro-Topographic variations Soil Marks • variation in mineralogy and moisture properties Differential Crop Marks • constraint on root depth and moisture availability changing crop stress/vigour Proxy Thaw Marks • Exploitation of different thermal capacities of objects expressed in the visual component as thaw marks Now you see me dont
- 6. Archaeological Prospection What is the basis for detection
- 7. Archaeological Prospection What is the basis for detection
- 8. Archaeological Prospection Summary The sensor must have: • The spatial resolution to resolve the feature • The spectral resolution to resolve the contrast • The radiometric resolution to identify the change • The temporal sensitivity to record the feature when the contrast is exhibited The image must be captured at the right time: • Different features exhibit contrast characteristics at different times
- 9. A multi-sensor environment: which includes ground survey and excavation
- 10. Why DART? Isn’t everything rosy in the garden?
- 11. Why DART? ‘Things’ are not well understood Environmental processes Sensor responses (particularly new sensors) Constraining factors (soil, crops etc.) Bias and spatial variability Techniques are scaling! • Geophysics! IMPACTS ON • Deployment • Management
- 12. Why DART? Precision agriculture Using science to maximise crop return
- 13. Why DART? Precision agriculture Outlier values are being controlled
- 14. Why DART? Traditional AP exemplar
- 15. Why DART? Traditional AP exemplar Significant bias in its application • in the environmental areas where it is productive (for example clay environments tend not to be responsive) • Surveys don’t tend to be systematic • Interpretation tends to be more art than science
- 16. What do we do about this? Go back to first principles: • Understand the phenomena • Understand the sensor characteristics • Understand the relationship between the sensor and the phenomena • Understand the processes better • Understand when to apply techniques
- 17. What do we want to achieve with this? Increased understanding which could lead to: • Improved detection in marginal conditions • Increasing the windows of opportunity for detection • Being able to detect a broader range of features
- 18. What do we do about this? Understand the phenomena How does the object generate an observable contrast to it's local matrix? • Physical • Chemical • Biological • etc Are the contrasts permanent or transitory?
- 19. What do we do about this? Understand the phenomena If transitory why are they occurring? • Is it changes in? • Soil type • Land management • Soil moisture • Temperature • Nutrient availability • Crop type • Crop growth stage
- 20. What do we do about this? Understand the relationship between the sensor and the phenomena
- 21. What do we do about this? Understand the relationship between the sensor and the phenomena Spatial Resolution
- 22. What do we do about this? Understand the relationship between the sensor and the phenomena Radiometric Resolution Radiometric resolution determines how finely a system can represent or distinguish differences of intensity
- 23. What do we do about this? Understand the relationship between the sensor and the phenomena Temporal Resolution
- 24. What do we do about this? Understand the relationship between the sensor and the phenomena Spectral(?) Resolution http://www.youtube.com/v/Nh-ZB5bxPhc
- 25. What do we do about this? Understand the processes better So what causes these localised variations? • Local conditions structure how any contrast difference is exhibited: • Soil type • Crop type • Moisture • Nutrients • Diurnal temperature variations
- 26. What do we do about this? Understand the processes better Expressed contrast differences change over time • Seasonal variations • crop phenology (growth) • moisture • temperature • nutrients • Diurnal variations • sun angle (topographic features) • temperature variations
- 27. What do we do about this? Understand the processes better Exacerbated by anthropogenic actions • Cropping • Irrigation • Harrowing
- 28. What do we do about this? Example from multi or hyper spectral imaging
- 29. DART
- 31. DART: Ground Observation Benchmarking Try to understand the periodicity of change • Requires • intensive ground observation • at known sites (and their surroundings) • In different environmental settings • under different environmental conditions
- 32. DART: Ground Observation Benchmarking Based upon an understanding of: • Nature of the archaeological residues • Nature of archaeological material (physical and chemical structure) • Nature of the surrounding material with which it contrasts • How proxy material (crop) interacts with archaeology and surrounding matrix • Sensor characteristics • Spatial, spectral, radiometric and temporal • How these can be applied to detect contrasts • Environmental characteristics • Complex natural and cultural variables that can change rapidly over time
- 33. DART: Sites Location • Diddington, Cambridgeshire • Harnhill, Gloucestershire Both with • contrasting clay and 'well draining' soils • an identifiable archaeological repertoire • under arable cultivation Contrasting Macro environmental characteristics
- 37. DART: Field Measurements Spectro-radiometry • Soil • Vegetation • Every 2 weeks Crop phenology • Height • Growth (tillering) Flash res 64 • Including induced events
- 38. DART: Field Measurements Resistivity Weather station • Logging every half hour
- 40. DART: Field Measurements Aerial data • Hyperspectral surveys • CASI • EAGLE • HAWK • LiDAR • Traditional Aerial Photographs
- 41. DART: Laboratory Measurements Geotechnical analyses Particle size Sheer strength etc. Geochemical analyses Plant Biology
- 42. DART: Laboratory Measurements Plant Biology • Soil and leaf water content • Rate of germination • Root studies (emergence) • Root length and density. • Growth analysis • Root – Shoot biomass ratio. • Number of Leaves • Total plant biomass • Number of Tillers • Biochemical analysis: Protein and • Stem length chlorophyll analysis. • Total plant height • Broad spectrum analysis of soil • Drought experiment (Nutrient content) and C-N ratios of leaf. • A - Ci Curve • Chlorophyll a fluorescence
- 43. DART ERT Ditch Rob Fry B’ham TDR Imco TDR Spectro-radiometry transect
- 44. DART ERT Ditch Rob Fry B’ham TDR Imco TDR Spectro-radiometry transect
- 45. DART – exemplars Hyperspectral (400-2500nm) ERT Ditch High resolution Vertical Rob Fry B’ham TDR Imco TDR Spectro-radiometry transect
- 46. DART – exemplars Airborne Laser Scanning Discrete Echo and Full Waveform ERT Ditch Rob Fry
- 47. DART – exemplars Obliques ERT Ditch UAV Rob Fry B’ham TDR
- 48. DART: Data so far - Temperature
- 49. DART: Data so far - Temperature
- 50. DART: Data so far - Permittivity TDR - How does it work • Sends a pulse of EM energy • Due to changes in impedance, at the start and at the end of the probe, the pulse is reflected back and the reflections can be identified on the waveform trace • The distance between these two reflection points is used to determine the Dielectric permittivity • Different soils have different dielectric permittivity • This needs calibrating before soil moisture can be derived from the sensors
- 51. DART: Data so far - Permittivity Further analysis of permittivity and conductivity against rainfall Linking the changes to the weather patterns Comparisons can be made between • Soils at different depths • Archaeological and non-archaeological features • Different soil types at the different locations Conversion to moisture content is also a priority
- 52. DART: Data so far – Earth Resistance
- 53. DART: Data so far – Earth Resistance Probe Separation (m) 0.25 0.5 0.75 1 June R 18.04742552 18.88545 18.896896 16.79403 July 19.13517794 17.15205 17.081613 15.01906 August #N/A #N/A #N/A #N/A Difference in magnitude September 8.841189868 13.255 14.512463 15.53069 Change of Contrast Factors with October 7.988128839 10.97714 12.217018 11.6229 20 Seasons Contrast Factor (%) 15 Twin Probe Electrode Seperation (m) 10 0.2 5 0.5 0.7 5 5 June July August September October 0.25 18.04742 19.13517 8.841189 7.988128 0.5 18.88544 17.15204 13.25500 10.97714 0.75 18.89689 17.08161 14.51246 12.21701 1 16.79403 15.01905 15.53069 11.62289
- 54. DART: Data so far – Earth Resistance
- 55. Spectro-radiometry: Methodology • Recorded monthly • Twice monthly at Diddington during the growing season • Transects across linear features • Taken in the field where weather conditions permit • Surface coverage evaluated using near-vertical photography • Vegetation properties recorded along transect • Chlorophyll (SPAD) • Height
- 58. Diddington transect 1: Spectroradiometry June 2011 0.12 R e l 0.1 a t i v 0.08 e r 0.06 e f l e 0.04 c t a n 0.02 c e 0 400 500 600 700 Wavelength (nm) 27/06/2011 Archaeology 27/6/2011 Outside archaeology 14/06/2011 Archaeology 14/06/2011 Outside archaeology 08/06/2011 Archaeology 08/06/2011 Outside archaeology
- 59. Diddington transect 1: Spectroradiometry June 2011 0.4 R 0.35 e l a 0.3 t i v 0.25 e r 0.2 e f l 0.15 e c t 0.1 a n c 0.05 e 0 350 450 550 650 750 850 950 1050 1150 1250 1350 1450 1550 1650 1750 1850 1950 2050 2150 2250 2350 2450 Wavelength (nm) 27/06/2011 Archaeology 27/6/2011 Outside archaeology 14/06/2011 Archaeology 14/06/2011 Outside archaeology 08/06/2011 Archaeolgy 08/06/2011 Outside archaeology
- 61. DART: Plant Biology Lab experiments conducted in collaboration with Leeds Plant Biology in 2011 and repeated in 2012 From soils at Quarry Field Soil structure appears to be the major component influencing root penetration and plant health
- 65. Open Data: Server (in the near future) The full project archive will be available from the server Raw Data Processed Data Web Services Will also include TDR data Weather data Subsurface temperature data Soil analyses spectro-radiometry transects Crop analyses Excavation data In-situ photos ETC.
- 66. Why are we doing this – spreading the love
- 67. Why are we doing this – it’s the right thing to do DART is a publically funded project Publically funded data should provide benefit to the public
- 68. Why are we doing this – IMPACT/unlocking potential More people use the data then there is improved impact Better financial and intellectual return for the investors
- 69. Why are we doing this – innovation Reducing barriers to data and knowledge can improve innovation
- 70. Why are we doing this – education To provide baseline exemplar data for teaching and learning
- 71. Why are we doing this – building our network Find new ways to exploit our data Develop contacts Write more grant applications
- 72. Discussion SFM Plant Biology Pushbroom Phenology High resolution frame Differential growth parameters Oblique and UAV Data mining (process from Topographic measurements) From SFM Environmental Full Waveform LiDAR Soils Detection Temperature Hyperspectral (including thermal) Spectral Analysis Visualization ERT and tomography Complex data!
- 73. Questions
- 74. Overview There is no need to take notes: Slides – http://goo.gl/ZHYaB Text – http://goo.gl/osQZi or http://goo.gl/M5Eu1 There is every need to ask questions The slides and text are release under a Creative Commons by attribution licence.
Notas do Editor
- Image re-used under a Creative Commons licence: http://www.flickr.com/photos/catikaoe/183454010/We identify contrast Between the expression of the remains and the local 'background' value In most scenarios direct contrast measurements are preferable as these measurements will have less attenuation.Proxy contrast measurements are extremely useful when the residue under study does not produce a directly discernable contrast or it exists in a regime where direct observation is impossible
- Traces can be identified through evidence Clusters of artefacts Chemical and physical residues Proxy biological variations Changes in surface relief
- Traces can be identified through evidence Clusters of artefacts Chemical and physical residues Proxy biological variations Changes in surface relief
- Image re-used under a Creative Commons licence: http://www.flickr.com/photos/arpentnourricier/2385863532Dependant on localised formation and deformation Environmental conditions Soil moisture Crop Temperature and emmisivity
- Image re-used under a Creative Commons licence: http://www.flickr.com/photos/dartproject/6001577156Dependant on localised formation and deformation Land management
- Image re-used under a Creative Commons licence: http://www.flickr.com/photos/dartproject/6001577156Dependant on localised formation and deformation Land management
- Satellite approaches should be considered in a multi-sensor environment which includes ground survey and excavationThe point is to learn more about the past
- Image re-used under a Creative Commons licence: http://www.flickr.com/photos/southernpixel/3480710493/Not really.We have great techniques but some are in danger of becoming redundant
- Image re-used under a Creative Commons licence: http://www.flickr.com/photos/san_drino/1454922072/Environmental processesSensor responses (particularly new sensors)Constraining factors (soil, crops etc.)Bias and spatial variabilityIMPACTS ONDeploymentManagement
- Image re-used under a Creative Commons licence: http://www.flickr.com/photos/jimmysmith/720356377/Changes in land management may reduce the appearance of the phenomena we seekUsing science to maximise crop return
- Image re-used under a Creative Commons licence: http://www.flickr.com/photos/tangyauhoong/4502062656/Actual crop returns controlled so they approximate towardsthe 'norm'NEW, i.e. not observed before, archaeology is contained within the tailsThese outlier values are being removed.The outlier is an exceptional year ;-)
- Reliant on specific seasonal and environmental conditions Increasingly extreme conditions are required for the detection of ‘new’ sitesLow understanding of the physical processes at play outside the visual wavelengths
- Significant bias in its application in the environmental areas where it is productive (for example clay environments tend not to be responsive) Surveys don’t tend to be systematic Interpretation tends to be more art than science
- Image re-used under a creative commons licence: http://www.flickr.com/photos/8203774@N06/2310292882/
- Image re-used under a creative commons licence: http://www.flickr.com/photos/8203774@N06/2310292882/
- Image re-used under a Creative Commons licence:How does the object generate an observable contrast to it's local matrix?PhysicalChemicalBiologicaletcAre the contrasts permanent or transitory?
- Image re-used under a Creative Commons licence:If transitory why are they occurring?Is it changes in?Soil typeLand managementSoil moistureTemperatureNutrient availabilityCrop typeCrop growth stage
- Image re-used under a Creative Commons licence:
- Image re-used under a Creative Commons licence: DARTSpatial Resolution You need enough to observe the object
- Image re-used under a Creative Commons licence: DARTRadiometric Resolution - You need enough to be able to physically detect the expressed differencesdetermines how finely a system can represent or distinguish differences of intensity is usually expressed as a number of levels or a number of bits for example 8 bits or 256 levels The higher the radiometric resolution, the better subtle differences of intensity or reflectivity can be represented Signal to noise ratios can be a problem Example It is difficult to detect small changes in growth if your ruler only measures to the nearect 10cms You need enough to be able to physically detect the expressed differences
- Image re-used under a Creative Commons licence: DARTYou need to know when to look for the difference
- Spectral Resolution You need to know what part of the spectrum to detect the expressed difference Unsure of the geophysical metaphor for this
- Image re-used under a Creative Commons licence: DARTSo what causes these localised variations?Local conditions structure how any contrast difference is exhibited:Soil typeCrop typeMoistureNutrientsDiurnal temperature variations
- Image re-used under a Creative Commons licence: DARTExpressed contrast differences change over timeSeasonal variationscrop phenology (growth)moisturetemperaturenutrientsDiurnal variationssun angle (topographic features)temperature variations
- Image re-used under a Creative Commons licence: DARTExacerbated by anthropogenic actionsCroppingIrrigationHarrowing
- Image re-used under a Creative Commons licence: DARTBut archaeology doesn't tend to produce spectral signatures Rather: produce localised disruptions to a matrix The nature of these disruptions vary and include: Changes to the soil structure Changes to moisture retention capacity Changes in geochemistry Changes in magnetic or acoustic properties Changes to topography At least one of these disruptions will produce a contrast which is detectable The challenge is What sensor to use The sensitivity of the sensor When to deploy the sensor
- Try to understand the periodicity of changeRequire intensive ground observation (spectro-radiometry, soil and crop analysis) at known sites (and their surroundings) in a range of different environments under different environmental conditions
- Based upon an understanding of:Nature of the archaeological residuesNature of archaeological material (physical and chemical structure)Nature of the surrounding material with which it contrastsHow proxy material (crop) interacts with archaeology and surrounding matrixSensor characteristicsSpatial, spectral, radiometric and temporalHow these can be applied to detect contrastsEnvironmental characteristicsComplex natural and cultural variables that can change rapidly over time
- LocationDiddington, CambridgeshireHarnhill, GloucestershireBoth withcontrasting clay and 'well draining' soilsan identifiable archaeological repertoireunder arable cultivationContrasting Macro environmental characteristics
- Image reused under a Creative Commons Licence:http://www.flickr.com/photos/kubina/279523019Geotechnical analysesGeochemical analysesPlant Biology
- Image reused under a Creative Commons Licence:http://www.flickr.com/photos/kubina/279523019Geotechnical analysesGeochemical analysesPlant Biology
- Image re-used under a creative commons licence:http://www.flickr.com/photos/soilscience/5104676427Spectro-radiometrySoilVegetationEvery 2 weeksCrop phenologyHeightGrowth (tillering)Flash res 64Including induced events
- ResistivityGround penetrating radarEmbedded Soil Moisture and Temperature probesLogging every hour Weather stationLogging every half hour
- Image reused under a Creative Commons Licence:http://www.flickr.com/photos/kubina/279523019Geotechnical analysesGeochemical analysesPlant Biology
- Aerial dataHyperspectral surveysCASIEAGLEHAWKLiDARTraditional Aerial Photographs
- Image reused under a Creative Commons Licence:http://www.flickr.com/photos/kubina/279523019Geotechnical analysesGeochemical analysesPlant Biology
- Image reused under a Creative Commons Licence:http://www.flickr.com/photos/kubina/279523019Geotechnical analysesGeochemical analysesPlant Biology
- TDR - How does it workSends a pulse of EM energyDue to changes in impedance, at the start and at the end of the probe, the pulse is reflected back and the reflections can be identified on the waveform traceThe distance between these two reflection points is used to determine the Dielectric permittivity Different soils have different dielectric permittivityThis needs calibrating before soil moisture can be derived from the sensors
- Further analysis of permittivity and conductivity against rainfall Linking the changes to the weather patternsComparisons can be made betweenSoils at different depthsArchaeological and non-archaeological featuresDifferent soil types at the different locations
- Conversion to moisture content is also a priorityRequires calibration using different mixing models including:empiricalsemi-empiricalphysical volumetric phenomenological modelsThis will help us to link the changes in geophysical responses to the composition of the soil and predict future responses, as well as supporting investigations into crop stress and vigour.
- Conversion to moisture content is also a priorityRequires calibration using different mixing models including:empiricalsemi-empiricalphysical volumetric phenomenological modelsThis will help us to link the changes in geophysical responses to the composition of the soil and predict future responses, as well as supporting investigations into crop stress and vigour.
- methodology similar to that employed by Parkyn et al. (2011)Overviewdata pointslie within the ditch featureover the non-archaeological featurefind an average data value for the feature and the surrounding soilThe percentage difference between these two figures can then be considered the amount of contrast within the test area.The higher the percentage, the better the feature is able to be defined.
- © NevitDilmen [CC-BY-SA-3.0 (www.creativecommons.org/licenses/by-sa/3.0) or GFDL (w