Whether caused by natural erosion or human activity (urbanisation, pollution, climate events, rising sea levels, etc.), more and more archaeological sites are under threat. Archaeologists are working against the clock to identify, document, and preserve places of interest before they are lost forever.
Thankfully, archaeology has come a long way over the years. Modern practitioners now have the help of analytical techniques to document artefacts and imaging technologies to find and map sites. Armed with new tools, the field aims to accelerate discoveries and better preserve historically significant locations.
One of these new technologies finding greater use across the field is hyperspectral imaging (HSI). A non-destructive technique, HSI provides data for imaging both large areas (to map archaeological sites and identify new areas for investigation) and smaller artefacts (delivering a more comprehensive analysis of archaeological objects).
HSI uses advanced optical techniques to deliver spectral information on top of a typical 2D image. While traditional cameras provide a 2D array of coloured pixels, HSI outputs a 3D hypercube with 30 or more data points representing the spectra incident on each pixel of the camera. These data points reveal spectral information and signatures to identify subtle differences in materials, surface characteristics, and pigments that would go unnoticed using traditional photography.
Multispectral imaging (a reduced form of HSI with roughly 10 data points per pixel) began to be used in art conservation during the early 1990s. Over the last ten years, HSI technology has crossed over from the art world, becoming a valuable imaging tool for archaeologists in the field. Hyperspectral systems are now robust and stable enough to provide fast and meaningful data outside of controlled environments. Allowing archaeologists to perform:
- Large-scale remote sensing with aerial and satellite data, mapping new sites and finding
- Non-destructive analysis of artefacts in significant detail, uncovering hidden details and
increasing our understanding of the history and culture behind archaeological finds
Identifying and mapping archaeological sites with more data than ever before
HSI’s main application within archaeology has been the use of satellite imaging to discover hidden features underground. This form of remote sensing offers unique data that would not be possible using more traditional techniques.
While satellite-based HSI provides useful archaeological information, the limited spatial resolution is not well suited to the discovery of small archaeological features. Therefore, HSI is also being utilised in aerial photography.
For the last hundred years, archaeological surveys for site discovery have been conducted using low-flying aircraft and traditional photography. This approach offers high spatial resolution, but vegetation and soil marks can go undetected in sub-optimal conditions with only three colour bands per pixel. Small differences in height or crop colour might be too low in contrast to be noticeable with traditional cameras.
With greater spectral resolution, hyperspectral cameras offer the extra detail needed to detect signs of subsurface structures key for discovering archaeological sites.
Previous hyperspectral systems were limited in their use for archaeological site discovery due to their reduced spatial resolution and the tremendous amount of data processing they required. Newer systems now offer the spectral and spatial resolution needed to improve the detection of archaeological markings and the data processing techniques required for high frame rates, extracting meaningful image cubes much faster than before.
With HSI, archaeologists can now:
- Highlight similarities and dissimilarities in the composition of materials to increase the
likelihood of detecting hidden subsurface structures
- Comprehensively map existing archaeological sites
- Highlight specific locations for further investigation and implement data-driven sampling
strategies for targeted analysis
- Track changes over time in order to protect and preserve historically significant locations
Analysing archaeological sites and artefacts in greater detail
HSI has also found use closer to the ground, with portable systems operating in the field to deliver enhanced analysis of archaeological sites and artefacts. Hyperspectral data offers a range of benefits to archaeologists, with use cases in material identification, vegetation analysis, preservation and restoration, and dating and chronology.
The key benefit of HSI, beyond its added spectral information, is that it is non-destructive.
Archaeological manuscripts, parchments, and artworks degrade with time. With hyperspectral systems, we can understand these artefacts without causing any further damage. HSI simply measures the reflected spectra an artefact produces, allowing researchers to examine its spectral response, returning previously undetected data. From this, it can:
- Reveal hidden information: Archaeological artefacts typically have secrets beyond what we can detect with the naked eye or traditional photography. Writings and artwork may have alterations, underlying sketches, or faded and hidden information. Perhaps there have been previous attempts to restore them over the centuries. All these can be revealed by analysing the reflected light across different wavelengths.
- Identifying pigments and dyes: HSI can also identify different types of pigments and dyes
used in ancient artworks or for decorating ceramics and pottery. Different pigments have
different spectral fingerprints that show up in the hyperspectral data. Previous techniques may require destructive chemical analysis to reveal the same information.
- Conservation: With accurate, high spectral resolution data, archaeologists and conservators can monitor changes over time, tracking natural degradation or issues caused by the transportation and storage of artefacts. This data can help improve conservation techniques and treatments, such as laser cleaning or tracking water absorption.
- Restoration: Beyond conservation, hyperspectral data can also be used to improve the
accuracy of restoration efforts for damaged or degraded antiques and relics. Hyperspectral data reveals the original pigments, materials, and even the artistic techniques first used. This information helps conservators make better decisions about how best to restore items.
The added information provided by HSI leads to new discoveries, improved preservation, and a greater understanding of the history and culture behind archaeological sites and artefacts.
Combining HSI with other techniques
While a great tool for archaeologists, HSI is just one of many available to them. Effective
archaeological practices utilise and combine various techniques to build the fullest picture available to them.
Hyperspectral data can be enriched by other techniques that, for example, provide chemical or molecular information about ancient remnants or relics. HSI is commonly combined with x-ray fluorescence, Raman spectroscopy, laser scanning, and micro-destructive techniques that deliver detailed chemical analysis of small samples.
Recent examples include:
- Combining HSI and x-ray fluorescence to uncover hidden details in two Egyptian paintings. Researchers discovered alterations made by the original artists by analysis on-site in the tombs using portable devices.
- Combining HSI with a chemometric model to generate chemical images of ancient bones, quantifying the distribution of collagen present.
Getting hyperspectral systems into the field
HSI is becoming a highly valuable tool for archaeology, providing non-destructive spectral and spatial data. For the technique to proliferate further, researchers need access to low-cost, portable, robust, and easy-to-use imagers capable of delivering accurate results in the field. They also need fast systems capable of compressing the tremendous amount of data collected to produce real-time images.
Get in touch today and learn more about how Living Optics is redefining the future of hyperspectral imaging.
Kama ni kutokana na uharibifu wa asili au shughuli za binadamu (urbanization, uchafuzi wa mazingira, matukio ya hali ya hewa, kuongezeka kwa viwango vya bahari, nk. Sehemu nyingi za kiakiolojia ziko hatarini. Wataalamu wa vitu vya kale wanafanya kazi kwa bidii ili kutambua, kuorodhesha, na kuhifadhi mahali penye kupendeza kabla ya kupotea milele. Kwa bahati nzuri, uchunguzi wa vitu vya kale umefanya maendeleo makubwa katika miaka iliyopita. Wataalamu wa kisasa sasa wana msaada wa mbinu za uchambuzi za kurekodi vitu vya kale na teknolojia za upigaji picha za kupata na kupanga ramani za maeneo. Kwa kuwa wana vifaa vipya, wataalamu hao wanataka kuharakisha uvumbuzi na kuhifadhi vizuri maeneo yenye umuhimu wa kihistoria. Moja ya teknolojia hizi mpya kupata matumizi makubwa katika uwanja ni hyperspectral imaging (HSI). HSI ni mbinu ya kugundua maeneo makubwa (kuchora ramani ya maeneo ya kiakiolojia na kutambua maeneo mapya ya uchunguzi) na vitu vidogo (kuandaa uchambuzi wa kina zaidi wa vitu vya kiakiolojia). HSI hutumia mbinu za hali ya juu za macho kutoa habari ya spectral juu ya picha ya kawaida ya 2D. Kamera za kawaida hutoa safu ya 2D ya pikseli za rangi, HSI hutoa hypercube ya 3D na pointi za data 30 au zaidi zinazowakilisha matukio ya spectra kwenye kila pixel ya kamera. Vitu hivi vya data hufunua habari za wigo na saini ili kutambua tofauti ndogo katika vifaa, sifa za uso, na rangi ambazo hazingegunduliwa kwa kutumia upigaji picha wa jadi. Picha za multispectral (a) ni aina ya HSI iliyopunguzwa na takriban pointi za data 10 kwa pixel, na (b) ni aina ya HSI iliyopunguzwa na kipimo cha data 10 kwa pixel. Katika miaka ya hivi karibuni, teknolojia ya HSI imepita kutoka ulimwengu wa sanaa, na kuwa chombo muhimu cha picha kwa wataalamu wa akiolojia katika uwanja. Mifumo ya hyperspectral sasa ni imara na imara ya kutosha kutoa data ya haraka na yenye maana nje ya mazingira kudhibitiwa. HSI inasaidia wataalamu wa vitu vya kale kufanya uchunguzi wa mbali kwa kiwango kikubwa na data ya anga na satellite, na kuunda ramani ya maeneo mapya na kugundua uchambuzi usio na uharibifu wa vitu vya kale kwa undani mkubwa, kufunua maelezo yaliyofichwa na kuongeza uelewa wetu wa historia na utamaduni nyuma ya vitu vya kale. Aina hii ya uchunguzi wa mbali hutoa data ya kipekee ambayo haiwezekani kutumia mbinu za jadi zaidi. Wakati satellite-msingi HSI hutoa muhimu archeological habari, mapungufu spatial azimio si vizuri suti kwa ajili ya ugunduzi wa vipengele vidogo archeological. Kwa hiyo, HSI pia ni kutumika katika upigaji picha wa angani. Kwa miaka mia moja iliyopita, uchunguzi wa kiakiolojia wa kugundua maeneo umefanywa kwa kutumia ndege zinazoruka kwa urefu wa chini na upigaji picha wa kitamaduni. Njia hii inatoa azimio la juu la nafasi, lakini mimea na alama za udongo zinaweza kutambuliwa katika hali za chini ya bora na bendi tatu tu za rangi kwa pixel. Tofauti ndogo katika urefu au rangi ya mazao inaweza kuwa chini sana katika tofauti kuwa noticeable na kamera ya jadi. Kwa azimio kubwa la spectral, kamera za hyperspectral hutoa maelezo ya ziada yanayohitajika kugundua ishara za miundo ya chini ya ardhi muhimu kwa kugundua maeneo ya akiolojia. Mifumo ya hyperspectral ya zamani ilikuwa na kikomo katika matumizi yao kwa ajili ya uvumbuzi wa tovuti ya akiolojia kutokana na azimio lao la nafasi iliyopunguzwa na kiasi kikubwa cha usindikaji wa data waliohitaji. Mifumo mpya sasa hutoa azimio la spectral na nafasi inayohitajika kuboresha utambuzi wa alama za akiolojia na mbinu za usindikaji wa data zinazohitajika kwa viwango vya fremu za juu, kutoa mchanganyiko wa picha zenye maana haraka zaidi kuliko hapo awali. HSI inaweza kuongeza uwezekano wa kugundua miundo ya chini ya ardhi iliyofichwa, na pia kuangazia maeneo maalum kwa uchunguzi zaidi na kutekeleza mikakati ya sampuli inayoendeshwa na data kwa uchambuzi wa lengo, kufuatilia mabadiliko kwa muda ili kulinda na kuhifadhi maeneo muhimu ya kihistoria, na kuchambua maeneo ya akiolojia na vitu vya kale kwa undani zaidi. Data ya hyperspectral inatoa faida mbalimbali kwa wataalamu wa akiolojia, na kesi za matumizi katika utambulisho wa vifaa, uchambuzi wa mimea, uhifadhi na ukarabati, na tarehe na kronolojia. Faida kuu ya HSI, zaidi ya habari yake ya wigo iliyoongezwa, ni kwamba sio ya uharibifu. Hati-mkono za kiakiolojia, maandishi ya ngozi, na kazi za sanaa huharibika kadiri wakati unavyopita. Kwa kutumia mifumo ya hyperspectral, tunaweza kuelewa vitu hivyo bila kusababisha uharibifu zaidi. HSI hupima tu spectra iliyoonyeshwa ambayo kiumbe hutengeneza, ikiruhusu watafiti kuchunguza majibu yake ya spectral, kurudisha data ambazo hazikuonekana hapo awali. "Kutokana na hili, inaweza: ""kufunua habari zilizofichwa: vitu vya kale vya kiakiolojia kwa kawaida vina siri zaidi ya kile tunachoweza kugundua kwa jicho la kawaida au upigaji picha wa jadi.""" Maandishi na michoro yaweza kuwa na marekebisho, michoro iliyo chini, au habari zilizofichwa na kufichwa. Labda kumekuwa na majaribio ya awali ya kuwarudisha kwa karne nyingi. Yote haya yanaweza kufunuliwa kwa kuchanganua mwanga unaorudishwa katika urefu tofauti wa mawimbi. HSI pia inaweza kutambua aina tofauti za rangi na rangi zilizotumiwa katika kazi za sanaa za kale au kwa mapambo ya kauri na udongo. Rangi tofauti zina alama tofauti za spectral ambazo huonekana katika data ya hyperspectral. Mbinu za awali zaweza kuhitaji uchambuzi wa kemikali wenye kuharibu ili kufunua habari ileile. - Uhifadhi: Kwa data sahihi, ya azimio la juu la spectral, wataalamu wa akiolojia na wasimamizi wanaweza kufuatilia mabadiliko kwa muda, kufuatilia uharibifu wa asili au masuala yanayosababishwa na usafirishaji na uhifadhi wa vitu vya kale. Takwimu hizi zinaweza kusaidia kuboresha mbinu za uhifadhi na matibabu, kama vile kusafisha kwa laser au kufuatilia kunyonya maji. - Kurudishwa: Mbali na uhifadhi, data ya hyperspectral pia inaweza kutumika kuboresha usahihi wa juhudi za kurudishwa kwa vitu vya kale na vitu vya kale vilivyoharibiwa au kuharibika. Takwimu za hyperspectral hufunua rangi za awali, vifaa, na hata mbinu za kisanii zilizotumiwa kwa mara ya kwanza. Habari hiyo husaidia wasimamizi wa vitu kufanya maamuzi mazuri kuhusu jinsi ya kurudisha vitu vizuri. Habari za ziada zinazotolewa na HSI husababisha uvumbuzi mpya, uhifadhi ulioboreshwa, na uelewa mkubwa wa historia na utamaduni nyuma ya maeneo ya akiolojia na vitu vya kale. HSI ni mojawapo ya mbinu nyingi zinazotumiwa na wataalamu wa vitu vya kale. Mazoea yenye matokeo ya akiolojia hutumia na kuchanganya mbinu mbalimbali ili kujenga picha kamili zaidi inayopatikana kwao. Takwimu za hyperspectral zinaweza kutajwa na mbinu nyingine ambazo, kwa mfano, hutoa habari za kemikali au molekuli kuhusu mabaki ya kale au mabaki. HSI kwa kawaida huunganishwa na X-ray fluorescence, Raman spectroscopy, laser scanning, na mbinu za kuharibu ndogo ambazo hutoa uchambuzi wa kina wa kemikali ya sampuli ndogo. Mifano ya hivi karibuni ni pamoja na: - Kuchanganya HSI na X-ray fluorescence kufunua maelezo yaliyofichwa katika michoro miwili ya Misri. Watafiti waligundua marekebisho yaliyofanywa na wasanii wa awali kwa kuchanganua makaburi hayo mahali hapo kwa kutumia vifaa vinavyoweza kubebwa. - Kuchanganya HSI na mfano chemometric kuzalisha picha za kemikali ya mifupa ya kale, quantifying usambazaji wa collagen sasa. HSI ni chombo muhimu sana kwa ajili ya akiolojia, kutoa data ya spectral na nafasi isiyo ya uharibifu. Ili mbinu hiyo iendelee kuenea, watafiti wanahitaji vifaa vya kupigia picha vya bei nafuu, vinavyoweza kubebwa, vyenye nguvu, na rahisi kutumia vinavyoweza kutoa matokeo sahihi shambani. Pia wanahitaji mifumo ya haraka inayoweza kukusanya kiasi kikubwa cha data zilizokusanywa ili kutokeza picha za wakati halisi. Kujiunga leo na kujifunza zaidi kuhusu jinsi Living Optics ni redefining siku zijazo ya hyperspectral imaging.