Search

The soils of southeast Asia include regionally extensive layers of generally sandy material, in some places 5m or more in depth, observed throughout Vietnam, Cambodia and Thailand, and upland areas of Myanmar and Malaysia, and even the Punjab. Various explanations for the origin of these layers have been proposed, with clarification of their ages and modes of emplacement remaining a significant issue. In many locations, these cover sands overlay a laterite layer containing tektites associated with a 750-800ka old meteorite impact in the region. \ud \ud Luminescence measurements have been used to date and characterise these sand layers, and in this report such measurements from five locations in Thailand and one site in Vietnam have been reviewed. This suggests that luminescence methods can readily distinguish between two distinct classes of material within these sand layers: 1. Sands with lower luminescence sensitivity and OSL depletion indices with ages in excess of ~50ka (the limit of SAR OSL methods); 2. Sands with high luminescence sensitivity and OSL depletion indices with ages less than 35ka. At four locations in Thailand only the younger material is present, with ages for basal samples of 9-35ka. At the other Thai site (Huai Om) both are present, with the older material in the lower 50cm of the section, and the young material immediately above this giving an age of approximately 30ka. At the site in Vietnam (Hue), there is evidence that the materials have experienced mixing, with some younger material within the older layer. The use of OSL intensities and depletion indices from the Portable OSL reader would be a method of rapidly distinguishing between these two classes of sand in the field. \ud \ud Dose extension methods have been used to estimate equivalent doses for the older materials. Applied to the younger materials, these give equivalent doses within 20% of the OSL method. For the older materials at Huai Om and Hue these give equivalent doses consistent with an age of 100-150ka, although the data suggest that the traps associated with these measurements have lifetimes of ~105 years at environmental temperatures of 25°C, which could significantly underestimate the age of these minerals. Further investigations into trap stability may be useful, including (if possible) collection of samples from equivalent contexts with lower environmental temperatures (eg: at higher altitude).

Previous optically stimulated luminescence (OSL) dating measurements conducted on samples collected from a sedimentary cover sands sequence in Vietnam indicated basal ages of 14.4 ± 2.1 ka from aliquots yielding finite age estimates. However, some aliquots were beyond the saturation point of the OSL dose response curve (>100Gy, or c. 50 ka). This implies the presence of older material within the deposits. Further investigations have therefore been under taken to investigate luminescence signals associated with deeper traps in these quartzes to extend the range of the dose response. \ud \ud Investigation using aliquots previously measured for OSL has shown that:\ud • Thermally transferred OSL (TT-OSL) produces signals at 1% or lower intensities than the OSL signals. For these quartzes the resulting signal intensities are too low to yield precise dose estimates. \ud • However both the thermoluminescence (TL) during the heating ramp to thermal transfer temperatures (TL-ramp) and isothermal decay (ID) during the thermal transfer period produce large signals whose dose response continues to beyond 500Gy. Since these signals also originate from deep traps following OSL stimulation and grow to high doses they were investigated further. \ud Using freshly dispensed aliquots of the quartz from the basal sample a new SAR dating run was performed, combined OSL, TL-ramp, I-Decay, and TT-OSL readout. As before TT-OSL intensities were low. However the other signals were measured at dose up to 1 kGy. It was possible to obtain finite dose estimates in the range of 200-250 Gy using TL-ramp and I-Decay signals. These correspond to ages of 100-125ka. This confirms the presence of older material in the basal samples. \ud \ud Since the basal samples may also be associated with microtektites of even greater age, a short kinetic analysis of the thermal activation energy and frequency factors associated with these signals was undertaken to evaluate their likely stability over a range of environmental temperatures. The outcome suggests thermal mean lives of 105-106 years at ambient temperatures in the 20-30°C region, with a strong dependence on environmental temperatures. Further work to extend the data sets to other cover sands in the region would potentially be useful.

The Pacific coast of the state of Nayarit, Mexico, is dominated by extensive sand dune systems and lagoons. 16 samples from three transects through dunes near the town of Santa Cruz were collected to establish ages of the beach dune ridges and establish a robust chronology, to assist in understanding the depositional rates associated with different phases of the evolution of the strand plain. In addition, three samples were collected from a fluvial terrace on the San Pedro River which enters the Pacific near the southernmost of the dune transects. Quartz grains were extracted from the samples, and analysed using an Optically Stimulated Luminescence (OSL) method to determine stored dose and ages.\ud \ud The samples collected nearest the current coast have produced dates of 1500-1900AD, with samples further from the coast being progressively older, spanning a period of over 2000 years with oldest measured date of 400BC. The dates for the upper samples from the San Pedro River is consistent with the ages of the dunes nearest the coast, with the lower sample date closer to the dates of the older dunes further from the coast, indicating that this fluvial deposit was laid down over the same time period as the dune formation.

Luminescence measurements have been conducted on small samples from a stratigraphic horizon in Vietnam overlaying a regionally extensive gravel layer containing tektites and shocked quartz that are evidence for a meteorite impact dated to approximately 700 ka. The lower part of this stratigraphic horizon contains coarser grains and smashed granules which may also be associated with the impact event. Profiling measurements of the same sedimentary feature in Thailand showed an inverted luminescence profile. The measurements conducted here show that these materials had been very well bleached prior to deposition, with bright rapidly depleting OSL signals from quartz grains. These samples do not reproduce the inverted sequence observed in Thailand. The OSL measurements suggest three distinct zones within the sedimentary sequence; the youngest 6-7 samples showing a steady increase in stored dose estimates, the middle 7-8 samples show approximately constant dose estimates, with a discontinuity in dose estimate above the oldest 7-8 samples which also show a higher OSL depletion rate and IRSL:OSL ratio. It is suggested that the data represent a history of rapid sedimentation depositing the lower zone, followed by an erosional event removing the upper part of this sequence, before a second period of rapid sedimentation with material potentially from a different source, and finally a more recent period of lower sedimentation rate. These samples appear to be very suitable for quantitative dating with sufficient material for dose rate determination in some instances, and could be considered for establishing a chronology for this stratigraphic sequence. Quantitative SAR OSL analysis has been conducted on three samples, one from each of the three zones, where control samples had been collected providing sufficient material for dose rate calculation. There are differences between the three samples in both dose rate (upper sample with the lowest dose rate and the lower sample the highest) and luminescence sensitivity (with the lowest sample being less sensitive), suggestive of differences in the source materials for each of the three zones. The SAR ages for the upper two samples are inverted and significantly different from the profiling apparent ages (16.0 ± 2.3 ka for the upper and 5.4 ± 0.7 ka for the middle sample). The lowest sample, just above the gravel layer containing shocked quartz and tektites, has an equivalent dose distribution with a broad peak corresponding to an age of 14 ± 2 ka, with several aliquots with equivalent doses that correspond to ages significantly in excess of 50 ka. The 14 ± 2 ka age is consistent with previous OSL ages for the corresponding sedimentary layer in Thailand (8 and 19 ka), which is significantly younger than the impact date and suggest that these layers are not associated with the impact. However, the significantly older ages for some samples may suggest an earlier deposition with subsequent disturbance introducing the younger material. Alternative quartz analysis methods would be needed to extend the range of measurement to explore the age of these older components.

This report concerns optically stimulated luminescence (OSL) investigations of sediments from the the foreshore at Burga Sands, Underhoull, and a dune section at Lund, in south-west Unst (Shetland). Samples were collected in February 2016 to establish the timing of sand accumulation, adding to an expanding set of dated sand blows in the Northern Isles and Scotland. The resulting chronologies define the local environmental record of sand movements in the vicinity of Underhoull and Lund, with their adjacent Norse longhouses and chapel. The sediment stratigraphies on the foreshore of Burga Sands were explored through four profiles, comprising the natural accumulations adjacent to two noosts (profiles 1 and 2), and the substrate sequences immediately beneath the noosts (P3&4). The dune section at Lund was explored in a single profile (P5).\ud This report describes the progression from fieldwork and sampling, through initial luminescence screening measurements made with the portable OSL reader (on 45 samples), to subsequent calibrated analysis in the laboratory, first, to characterise the OSL and IRSL signals from each sample, then by targeted quantitative OSL dating on a further set of 10 samples. The ‘field profiles’ provided the first indication that the substrate stratigraphies at Underhoull, extend from the late glacial period to the modern day. The maxima and dynamic ranges in signal intensities for the sequences beneath the noosts, suggest that the construction and modification of these structures were temporally distinct. For the Lund section, the range in signal intensities through\ud these sediments, indicate a shorter chronology, which was confirmed by subsequent characterisation of the profiling samples in the laboratory.\ud The following chronology was obtained for the Underhoull section:\ud 1) onset of sand activity, as recorded in the sedimentary archives of profiles 1 and 2, at 3.22 ± 0.29 ka (1210 ± 290BC; SUTL2861) and 1.99 ± 0.15 ka (AD30 ± 150; SUTL2863)\ud 2) modification and re-build of the first noost at 0.48 ± 0.06 ka (AD1540 ± 60; SUTL2866)\ud 3) construction of the second noost at 0.81 ± 0.07 ka (AD1210 ± 70; SUTL2867)\ud 4) continued sand movements into the early 20th century AD (0.12 ± 0.06 ka; AD1900 ± 60; SUTL2862), with arguably heightened activity at the onset of the Little Ice Age (0.64 ± 0.10 ka; AD 1380 ± 60; SUTL2866).\ud For the Lund dune section, the sediment chronology spans from the early 14th century AD through to the early 18th century AD (0.70 ± 0.05 ka; SUTL2868, through 0.52 ± 0.04 ka; SUTL2869, to 0.31 ± 0.02 ka; SUTL2870), corresponding with the onset and waning stages of the Little Ice Age. \ud The chronology presented here is consistent with an emerging regional framework of sand movements in the Northern Isles and Scotland, with activity in the Neolithic, Early and Late Bronze Ages, the Iron Age, the Viking/Medieval period, and Little Ice Age. The Underhoull section dated here provides a broad chronology for sand blow and, importantly, places sediments underneath two noosts into the late Norse/ Mediaeval period. The dune section dates a high resolution local record within the last 700 years. Opportunities to extend the high resolution palaeoenvironmental record were identified in the adjacent land and dune-scape, and especially in the palaeo-loch landward of the Lund section, which has received sand in the past.

Single grain optically stimulated luminescence (OSL) measurements have been conducted on retained material from sediment samples collected during excavations of Neolithic monuments at Capu di Locu, Belvédère, SW Corsica. One sample was taken from a presumed burial chamber at Tola and two from the lower fill of the construction pit of a menhir at Stantare. Analysis was conducted on 150-250 µm quartz grains previously separated for single aliquot regeneration (SAR) measurements, and on 250-500 µm grains prepared for this analysis. Single grain measurements, including analysis of blank discs prior to dispensing mineral grains, were conducting on a Risø DA-20 automatic reader, with 800-1000 grains measured for each of two samples, and approximately 350 grains for the third sample. \ud \ud These exploratory measurements have demonstrated that a relatively large proportion (>20%) of mineral grains produce significant OSL counts for both the natural stored dose and following a 25 Gy artificial dose. Previous analysis of these samples using multi-grain aliquots measured using a single aliquot regeneration (SAR) protocol had shown broad dose distributions, with mixtures of aliquots of different ages. The single grain measurements have confirmed that these are mixed age deposits. Two samples show stored dose distributions around mean values which correspond to archaeological ages, for the third the stored dose distribution is significantly broader with no apparent archaeological age component. Further statistical analysis of these data would be required to attempt to resolve archaeological age material, that could potentially be used to further constrain construction dates for these monuments. It is expected that similar luminescence properties would be exhibited by mineral grains from other samples collected during the excavations of these sites, and it is possible that further single grain OSL analysis of other parts of the site may produce dose distributions with less mixing and more readily resolved components with archaeological ages. \ud \ud Meanwhile SG apparent ages were obtained from the Tola sample which are consistent with previous estimates, and two new estimates have been achieved from the Stantare site which indicate potential for recovering archaeological ages in the 3rd to 4th millennium BC from the Menhir site.

This report is concerned with optically stimulated luminescence (OSL) investigations of a number of sediment stratigraphies in the Battle River Valley area, near Hardisty, east-central Alberta. Archaeological investigations in this region, led by Rob Wondrasek, have identified thousands of historical artefacts, including projectile points and lithic fragments indicative of occupation. Ken Munyikwa visited the archaeological sites at Hardisty in June 2014 and January 2015 to sample key units within the sediment stratigraphies for OSL dating. The sediments associated with the artefacts were appraised through five profiles, Hardisty-1 (HD01) to Hardisty-5 (HD05), comprised of 43 field-profiling and 14 dating samples. Profiles HD01 and HD02 were sampled in June 2014; and profiles HD03 through to HD05 in January 2015. The dating questions associated with these materials relate to the age of artefact-bearing horizon, through dating the enclosing sediments above and beneath the archaeological soil, it should be possible to provide terminus post quem (TPQ) and terminus ante quem (TAQ) on the age of the artefacts. \ud The conventional quartz SAR OSL approach was examined as a potential method for providing the depositional ages of the sediment enclosing the artefacts. Luminescence profiling during fieldwork had revealed stratigraphically progressive IRSL and OSL signals, indicating sediment with dating potential. Dose rate estimates from these sediments were assessed using a combination of high resolution gamma spectrometry (HRGS) and thick source beta counting (TSBC), reconciled with each other, water contents and modelled micro-dosimetry. Where appropriate, the external gamma dose rates received at the position of the dating sample were reconstructed from the adjacent bulk gamma spectrometry samples, yielding wet gamma dose rates between 0.42 and 0.54 mGy a-1, which are comparable with those recorded at each sampling position.\ud Equivalent doses were determined by OSL from 16-48 aliquots of quartz per sample (depending on quartz yields) using a single-aliquot-regenerative (SAR) approach. The material exhibited good OSL sensitivity and produced acceptable SAR internal quality control performance. Radial plotting methods revealed some heterogeneity in the equivalent dose distributions of each sample, indicating that each sample enclosed mixed-age materials, reflecting variable bleaching at deposition. The field profiles provide some measure of control on this. Luminescence ages were calculated using standard microdosimetric models, with uncertainties that combined measurement and fitting errors from the SAR analysis, all dose rate evaluation uncertainties, and allowance for the calibration uncertainties of the sources and reference materials.\ud The quartz OSL ages reported here for the sand sequences at HD03 to HD05, contribute to the expanding catalogue of chronological data on the depositional sequences at Hardisty, and further, provide the means to assess the temporal and spatial distribution of artefacts across the site. The sediment chronologies established for each profile are internally and mutually coherent, spanning at HD03 from 7.3 ± 0.3 ka (SUTL2778) to 9.0 ± 0.5 ka (SUTL2780), at HD04 from 7.0 ± 0.3 ka (SUTL2781) to 8.3 ± 0.4 ka (SUTL2782), and at HD05 from 8.3 ± 0.5 ka (SUTL2783) to 9.6 ± 0.6 ka (SUTL2785). The field profile at HD05 reveals some complexity to its depositional history, with notable maxima and inversions in intensities from 150cm depth, potentially reflecting reworking and re-deposition of sediment within this sequence. TAQ for this phase of reworking is provided by the youngest unit examined in the profile, which at 7.5 ± 0.6 ka (SUTL2784), is consistent with the occupational phase recorded in the adjacent sections. The sediment chronologies established in this dating campaign, and in the 2014 campaign, are synchronous suggesting contemporaneous deposition across the site, and presumably, with local knowledge, scope for further age modelling including the use of Bayesian methods to refine the TAQ and TPQ age limits.

This report provides a temporal framework to support University of Stirling geo-archaeological investigations near Huesbreck, Broo Pennisula (Shetland), examining how the early modern population there, adapted to harsh climate conditions in the 18-19th centuries, when enhanced aeolian activity led to an influx of sand to the area, leading to adaption’s in farming practices, and abandonment of several sites. Five sediment samples were submitted to the luminescence laboratories at SUERC for dating. \ud \ud All samples were subjected to laboratory preparation of sand-sized quartz, and purity checked using scanning electron microscopy. Dose rates for the bulk sediment were evaluated using analyses of the uranium, thorium and potassium concentrations obtained by high resolution gamma spectrometry coupled with beta dose rate measurement using thick source beta counting, and in situ field gamma spectroscopy. Equivalent doses were determined by OSL from 32 aliquots of quartz per sample using the quartz single-aliquot-regenerative (SAR) procedure. The material exhibited good OSL sensitivity and produced acceptable SAR internal quality control performance. Radial plotting methods revealed good internal homogeneity in the dose distributions obtained for each sample.\ud \ud The chronology established for the sampled sands on the site spans from the mid 16th century (AD 1540 ± 40; SUTL2441) through to the early 19th century (AD 1810 ± 25), with the dates falling within three clusters - the waning stages of the Little Ice Age, the mid 18th century (AD 1730 ± 25 to 1760 ± 25) and the early 19th century (AD 1810 ± 25). In the wider region, periods of sand movement and deposition in the mid 18th century, and early to late 18th century, are documented in sediment statigraphies sectioned at the Old Scatness Broch, Scatness.

Luminescence has the potential to elucidate glacial geomorphic processes because primary glacial sediment sources and transport pathways are associated with contrasting degrees of exposure to light. Most notably, sediment entrained from extraglacial sources should be at least partially reset, whereas sediment produced by glacial erosion of subglacial bedrock should retain substantial luminescence commensurate with a geological irradiation history. We set out to test the validity of this assumption at Haut Glacier d'Arolla, Switzerland using sediment sampled extraglacially and from the glacier bed. Contrary to our expectations, the subglacial samples exhibited natural signals that were substantially lower than those of other sample groups, and further (albeit limited) analyses have indicated no obvious differences in sample‐group luminescence characteristics or behaviour that could account for this observation. For glaciological reasons, we can eliminate the possibilities that the subglacial sediment has been extraglacially reset or exposed in situ to heat or light. We therefore advocate investigation of possible resetting processes related to subglacial crushing and grinding, and speculate that such processes, if more generally present, may enable the dating of subglacially deposited tills using luminescence‐based techniques.

Environmental radioactivity arises from natural geological sources, the redistribution of natural activity through industrial processes, the nuclear industry including routine and accidental discharges into the environment, and various medical or industrial uses of radioisotopes. Mobile gamma spectrometry provides a powerful means of measuring the distribution of radioactivity in the environment. Data collected by such methods provide measures of environmental quality, references for public health assurance, means to assess environmental change, and other uses. Airborne Gamma Spectrometry (AGS) has been developed at SUERC for environmental purposes since 1988, and provides a capability for very rapid and cost effective surveys of large areas, and provides for visualisation and classification of enhanced features of radioactivity within the context of natural variations. Ground based approaches, with equipment mounted on vehicles or backpacks, provide more detailed spatial resolution for smaller areas at significantly reduced area coverage rates.\ud \ud A portable gamma spectrometry system has been developed at SUERC, consisting of a 3x3” NaI(Tl) detector with a digital spectrometer and GPS receiver using a netbook computer for\ud data acquisition. This system can be carried as a backpack and used to conduct surveys of environmental radioactivity in urban areas, where people spend their time.\ud \ud Detector backgrounds and stripping matrices have been measured. A survey of approximately 50,000 m2 of the Scottish Enterprise Technology Park (SETP) has been conducted with two detector systems. The SETP is on the site of the National Engineering Laboratory (NEL) established in East Kilbride in 1948, and acquired by Scottish Enterprise in 1994. In recent years there has been an ongoing programme of renovation on the site, including demolition of old buildings and new construction along with landscaping operations.\ud \ud This report presents the results of initial detector characterisation and the survey of part of the SETP site. Detector stripping matrices were determined from measurements made on the 18th August 2009, with background measurements on Loch Lomond collected on the 28th. The site\ud survey was conducted between 17th and 19th August 2009, with over 4600 spectra with 10s integration time collected. Maps of the distribution of 137Cs, 40K, 214Bi, 208Tl and gamma dose rate were produced. The 137Cs activity clearly shows areas undisturbed since 1986, with fallout from the Chernobyl accident still present on the grass. The footprint of the demolished research reactor at SUERC is evident as a negative feature in the 137Cs map. The natural\ud series activities and gamma dose rate show the range of materials used for building and road construction, including one small area of Technologically Enhanced Naturally Occurring Radioactive Material (TENORM), and the local geology and soils. This demonstrates the capability of the SUERC portable gamma spectrometry system to collect high quality data of an area with a complex history, land use and range of buildings. Further application of the\ud technique to other urban areas, and the rest of the SETP site, would allow similar assessments of the radiation environments of a range of different locations.

Previous Optical Stimulated Luminescence (OSL) investigations of irrigation features and archaeological sites in the hinterland around Anuradhapura, Sri Lanka, had observed highly heterogeneous dose distributions and apparent ages older than expected for bunds and similar constructions. These observations are consistent with utilising older sedimentary materials, which did not have their luminescence signals reset during construction.\ud The work reported here consists of OSL measurements from two sites in the Anuradhapura region. The first is a modern bund, sampled to examine the degree of heterogeneity of the dose distributions from a control structure. Two samples were taken from within this bund, one near the top and the other just above the land surface the bund was built upon. These show dose distributions that are highly heterogeneous with apparent ages in excess of 1500 years. The third sample from this site is from the truncated land surface beneath the bund, and gives a luminescence age of 150 ± 40 years with just one much older aliquot.\ud The second site in this work is an abandoned red-earth platform site, covered by an extensive layer of cultural deposits. A sample from the overlying deposits just above the constructed platform gives a luminescence age of 540 ± 70 years, with a homogenous dose distribution. A sample from near the top of the constructed platform gives a heterogeneous dose distribution and apparent ages up to 4000 years.\ud The results support the inferences from earlier sampling, providing clear confirmation that platform sites contain unbleached, re-deposited sediments, with significant residual OSL ages. The OSL results from the underlying land surfaces, and from slowly accumulated abandonment layers, appear to be consistent with external age control where available and thus are to be preferred as targets for OSL dating in such geo-archaeological investigations.

This study supports a new investigation into the construction, occupation and utilisation history of a Mediaeval ring fort near Newry, southwest Northern Ireland\ud (section 2). Optically stimulated luminescence (OSL) profiling and age determinations have been made for two sequences of sediments accumulated in the ring ditch surrounding the fort, and potential has been assessed for TL dating of a Souterrain-Ware sherd from a pit feature within the site complex (section 3). The archaeological significance of the age determinations has been reviewed in the light of the luminescence results and the samples’ depositional contexts, to constrain the deposition/formation dates of the sampled sediments (section 6).\ud \ud A total of 31 profiling (sections 5.1, 5.2) and 12 age (section 5.5) determinations were made. Profiling measurements were made using simplified equivalent dose\ud determination procedures on polymineral coarse and hydrofluoric etched sand-sized mineral grains (sections 4.2.2). Dose rate determinations were made using thick\ud source beta counting, high-resolution gamma spectrometry, field gamma spectrometry, measured water contents and calculated cosmic dose rates (sections 4.2.1 and 5.3). Equivalent dose determinations were made (sections 4.2.2, 5.4) using the OSL signals from sand sized grains of quartz separated from each sample.\ud \ud The luminescence behaviour of the Newry Ringfort samples was generally very good. Profiling indicated variable levels of residual luminescence signal through the\ud sections (sections 5.1, 5.2), but OSL on the etched fraction was found to be least affected, and measurements on fully prepared quartz for dating appeared even less so\ud (sections 6.1, 6.2). Dose rates ranged from 2.6 to 3.9 mGy/a, De values from the dating samples ranged from 0.7 to 5.0 Gy. Estimates of sediment accumulation date ranged from 410AD to 1750AD (section 5.5). Uncertainties on the age estimates were commonly around 3%, but young samples with scattered equivalent dose distributions had estimated age uncertainties of up to 11%.\ud \ud The external dose rate to the sherd was estimated to be 1.33 mGy/a ± 0.12 (sections 6.3, 7). Precision was limited by uncertainties in average water content during burial\ud rather than heterogeneity in the gamma radiation field: providing the range of sediment radioactivity at a site can be assessed, and the average burial water contents\ud of sherds excavated from it can be well constrained, then it is likely that sherds from around a site could be dated with sufficient precision to establish a broad chronology\ud for Souterrain-Ware.\ud \ud The earliest sediments in the ditch of the ringfort indicated that its construction predates the end of the 6th Century AD (sections 6.4, 7). These and other OSL age\ud estimates indicated continued occupation until the mid 11th Century, or phases of occupation in the 7th, 9th and 11th Centuries. Results from the base of a colluvial soil\ud sealing these layers indicate that the site was set to cultivation at or around the time of the Norman invasion of Ireland (1169AD), rather than in the post Mediaeval period.\ud Abandonment of the ringfort must have occurred at the time of the invasion or in the century before it. Samples from throughout the colluvial soil also indicated that it\ud continued to accumulate until at least the 18th Century, and probably into the 20th Century.

Airborne Gamma Spectrometry (AGS) is well suited to the mapping of radioactivity in the environment. Flight parameters (e.g. speed and line spacing) directly affect the rate of area coverage, cost, and data quality of any survey. The influences of line spacing have been investigated for data from inter‐tidal, coastal and upland environments with a range of 137Cs activity concentrations and depositional histories. Estimates of the integrated 137Cs activity (‘inventory’) within specified areas and the shapes of depositional features were calculated for subsets of the data at different line spacings. Features with dimensions greater than the line spacing show variations in inventory and area of less than 3%, and features with dimensions less than the line spacing show larger variations and a decreased probability of detection. The choice of line spacing for a task is dependent on the dimensions of the features of interest and required edge definition. Options for line spacing for different tasks are suggested. It is noted that for regional mapping, even 5–10 km line spacing can produce useful data.